2 /* pngread.c - read a PNG file
4 * Last changed in libpng 1.6.17 [March 26, 2015]
5 * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
22 #ifdef PNG_READ_SUPPORTED
24 /* Create a PNG structure for reading, and allocate any memory needed. */
25 PNG_FUNCTION(png_structp,PNGAPI
26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
29 #ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
31 error_fn, warn_fn, NULL, NULL, NULL);
33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
34 warn_fn, NULL, NULL, NULL);
37 /* Alternate create PNG structure for reading, and allocate any memory
40 PNG_FUNCTION(png_structp,PNGAPI
41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
51 png_ptr->mode = PNG_IS_READ_STRUCT;
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
63 /* In stable builds only warn if an application error can be completely
66 # if PNG_RELEASE_BUILD
67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
75 png_set_read_fn(png_ptr, NULL, NULL);
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
92 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
98 png_debug(1, "in png_read_info");
100 if (png_ptr == NULL || info_ptr == NULL)
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
111 /* IDAT logic needs to happen here to simplify getting the two flags
114 if (chunk_name == png_IDAT)
116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
126 png_ptr->mode |= PNG_HAVE_IDAT;
129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
130 png_ptr->mode |= PNG_AFTER_IDAT;
132 /* This should be a binary subdivision search or a hash for
133 * matching the chunk name rather than a linear search.
135 if (chunk_name == png_IHDR)
136 png_handle_IHDR(png_ptr, info_ptr, length);
138 else if (chunk_name == png_IEND)
139 png_handle_IEND(png_ptr, info_ptr, length);
141 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
142 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
144 png_handle_unknown(png_ptr, info_ptr, length, keep);
146 if (chunk_name == png_PLTE)
147 png_ptr->mode |= PNG_HAVE_PLTE;
149 else if (chunk_name == png_IDAT)
151 png_ptr->idat_size = 0; /* It has been consumed */
156 else if (chunk_name == png_PLTE)
157 png_handle_PLTE(png_ptr, info_ptr, length);
159 else if (chunk_name == png_IDAT)
161 png_ptr->idat_size = length;
165 #ifdef PNG_READ_bKGD_SUPPORTED
166 else if (chunk_name == png_bKGD)
167 png_handle_bKGD(png_ptr, info_ptr, length);
170 #ifdef PNG_READ_cHRM_SUPPORTED
171 else if (chunk_name == png_cHRM)
172 png_handle_cHRM(png_ptr, info_ptr, length);
175 #ifdef PNG_READ_gAMA_SUPPORTED
176 else if (chunk_name == png_gAMA)
177 png_handle_gAMA(png_ptr, info_ptr, length);
180 #ifdef PNG_READ_hIST_SUPPORTED
181 else if (chunk_name == png_hIST)
182 png_handle_hIST(png_ptr, info_ptr, length);
185 #ifdef PNG_READ_oFFs_SUPPORTED
186 else if (chunk_name == png_oFFs)
187 png_handle_oFFs(png_ptr, info_ptr, length);
190 #ifdef PNG_READ_pCAL_SUPPORTED
191 else if (chunk_name == png_pCAL)
192 png_handle_pCAL(png_ptr, info_ptr, length);
195 #ifdef PNG_READ_sCAL_SUPPORTED
196 else if (chunk_name == png_sCAL)
197 png_handle_sCAL(png_ptr, info_ptr, length);
200 #ifdef PNG_READ_pHYs_SUPPORTED
201 else if (chunk_name == png_pHYs)
202 png_handle_pHYs(png_ptr, info_ptr, length);
205 #ifdef PNG_READ_sBIT_SUPPORTED
206 else if (chunk_name == png_sBIT)
207 png_handle_sBIT(png_ptr, info_ptr, length);
210 #ifdef PNG_READ_sRGB_SUPPORTED
211 else if (chunk_name == png_sRGB)
212 png_handle_sRGB(png_ptr, info_ptr, length);
215 #ifdef PNG_READ_iCCP_SUPPORTED
216 else if (chunk_name == png_iCCP)
217 png_handle_iCCP(png_ptr, info_ptr, length);
220 #ifdef PNG_READ_sPLT_SUPPORTED
221 else if (chunk_name == png_sPLT)
222 png_handle_sPLT(png_ptr, info_ptr, length);
225 #ifdef PNG_READ_tEXt_SUPPORTED
226 else if (chunk_name == png_tEXt)
227 png_handle_tEXt(png_ptr, info_ptr, length);
230 #ifdef PNG_READ_tIME_SUPPORTED
231 else if (chunk_name == png_tIME)
232 png_handle_tIME(png_ptr, info_ptr, length);
235 #ifdef PNG_READ_tRNS_SUPPORTED
236 else if (chunk_name == png_tRNS)
237 png_handle_tRNS(png_ptr, info_ptr, length);
240 #ifdef PNG_READ_zTXt_SUPPORTED
241 else if (chunk_name == png_zTXt)
242 png_handle_zTXt(png_ptr, info_ptr, length);
245 #ifdef PNG_READ_iTXt_SUPPORTED
246 else if (chunk_name == png_iTXt)
247 png_handle_iTXt(png_ptr, info_ptr, length);
251 png_handle_unknown(png_ptr, info_ptr, length,
252 PNG_HANDLE_CHUNK_AS_DEFAULT);
255 #endif /* SEQUENTIAL_READ */
257 /* Optional call to update the users info_ptr structure */
259 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
261 png_debug(1, "in png_read_update_info");
265 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
267 png_read_start_row(png_ptr);
269 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
270 png_read_transform_info(png_ptr, info_ptr);
276 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
278 png_app_error(png_ptr,
279 "png_read_update_info/png_start_read_image: duplicate call");
283 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
284 /* Initialize palette, background, etc, after transformations
285 * are set, but before any reading takes place. This allows
286 * the user to obtain a gamma-corrected palette, for example.
287 * If the user doesn't call this, we will do it ourselves.
290 png_start_read_image(png_structrp png_ptr)
292 png_debug(1, "in png_start_read_image");
296 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
297 png_read_start_row(png_ptr);
299 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
301 png_app_error(png_ptr,
302 "png_start_read_image/png_read_update_info: duplicate call");
305 #endif /* SEQUENTIAL_READ */
307 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
308 #ifdef PNG_MNG_FEATURES_SUPPORTED
309 /* Undoes intrapixel differencing,
310 * NOTE: this is apparently only supported in the 'sequential' reader.
313 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
315 png_debug(1, "in png_do_read_intrapixel");
318 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
321 png_uint_32 row_width = row_info->width;
323 if (row_info->bit_depth == 8)
328 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
331 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
337 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
339 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
340 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
343 else if (row_info->bit_depth == 16)
348 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
351 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
357 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
359 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
360 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
361 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
362 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
363 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
364 *(rp ) = (png_byte)((red >> 8) & 0xff);
365 *(rp + 1) = (png_byte)(red & 0xff);
366 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
367 *(rp + 5) = (png_byte)(blue & 0xff);
372 #endif /* MNG_FEATURES */
375 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
377 png_row_info row_info;
382 png_debug2(1, "in png_read_row (row %lu, pass %d)",
383 (unsigned long)png_ptr->row_number, png_ptr->pass);
385 /* png_read_start_row sets the information (in particular iwidth) for this
388 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
389 png_read_start_row(png_ptr);
391 /* 1.5.6: row_info moved out of png_struct to a local here. */
392 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
393 row_info.color_type = png_ptr->color_type;
394 row_info.bit_depth = png_ptr->bit_depth;
395 row_info.channels = png_ptr->channels;
396 row_info.pixel_depth = png_ptr->pixel_depth;
397 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
399 #ifdef PNG_WARNINGS_SUPPORTED
400 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
402 /* Check for transforms that have been set but were defined out */
403 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
404 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
405 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
408 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
409 if ((png_ptr->transformations & PNG_FILLER) != 0)
410 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
413 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
414 !defined(PNG_READ_PACKSWAP_SUPPORTED)
415 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
416 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
419 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
420 if ((png_ptr->transformations & PNG_PACK) != 0)
421 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
424 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
425 if ((png_ptr->transformations & PNG_SHIFT) != 0)
426 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
429 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
430 if ((png_ptr->transformations & PNG_BGR) != 0)
431 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
434 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
435 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
436 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
439 #endif /* WARNINGS */
441 #ifdef PNG_READ_INTERLACING_SUPPORTED
442 /* If interlaced and we do not need a new row, combine row and return.
443 * Notice that the pixels we have from previous rows have been transformed
444 * already; we can only combine like with like (transformed or
445 * untransformed) and, because of the libpng API for interlaced images, this
446 * means we must transform before de-interlacing.
448 if (png_ptr->interlaced != 0 &&
449 (png_ptr->transformations & PNG_INTERLACE) != 0)
451 switch (png_ptr->pass)
454 if (png_ptr->row_number & 0x07)
457 png_combine_row(png_ptr, dsp_row, 1/*display*/);
458 png_read_finish_row(png_ptr);
464 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
467 png_combine_row(png_ptr, dsp_row, 1/*display*/);
469 png_read_finish_row(png_ptr);
475 if ((png_ptr->row_number & 0x07) != 4)
477 if (dsp_row != NULL && (png_ptr->row_number & 4))
478 png_combine_row(png_ptr, dsp_row, 1/*display*/);
480 png_read_finish_row(png_ptr);
486 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
489 png_combine_row(png_ptr, dsp_row, 1/*display*/);
491 png_read_finish_row(png_ptr);
497 if ((png_ptr->row_number & 3) != 2)
499 if (dsp_row != NULL && (png_ptr->row_number & 2))
500 png_combine_row(png_ptr, dsp_row, 1/*display*/);
502 png_read_finish_row(png_ptr);
508 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
511 png_combine_row(png_ptr, dsp_row, 1/*display*/);
513 png_read_finish_row(png_ptr);
520 if ((png_ptr->row_number & 1) == 0)
522 png_read_finish_row(png_ptr);
530 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
531 png_error(png_ptr, "Invalid attempt to read row data");
533 /* Fill the row with IDAT data: */
534 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
536 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
538 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
539 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
540 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
542 png_error(png_ptr, "bad adaptive filter value");
545 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
546 * 1.5.6, while the buffer really is this big in current versions of libpng
547 * it may not be in the future, so this was changed just to copy the
550 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
552 #ifdef PNG_MNG_FEATURES_SUPPORTED
553 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
554 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
556 /* Intrapixel differencing */
557 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
561 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
562 if (png_ptr->transformations)
563 png_do_read_transformations(png_ptr, &row_info);
566 /* The transformed pixel depth should match the depth now in row_info. */
567 if (png_ptr->transformed_pixel_depth == 0)
569 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
570 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
571 png_error(png_ptr, "sequential row overflow");
574 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
575 png_error(png_ptr, "internal sequential row size calculation error");
577 #ifdef PNG_READ_INTERLACING_SUPPORTED
578 /* Expand interlaced rows to full size */
579 if (png_ptr->interlaced != 0 &&
580 (png_ptr->transformations & PNG_INTERLACE) != 0)
582 if (png_ptr->pass < 6)
583 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
584 png_ptr->transformations);
587 png_combine_row(png_ptr, dsp_row, 1/*display*/);
590 png_combine_row(png_ptr, row, 0/*row*/);
597 png_combine_row(png_ptr, row, -1/*ignored*/);
600 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
602 png_read_finish_row(png_ptr);
604 if (png_ptr->read_row_fn != NULL)
605 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
608 #endif /* SEQUENTIAL_READ */
610 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
611 /* Read one or more rows of image data. If the image is interlaced,
612 * and png_set_interlace_handling() has been called, the rows need to
613 * contain the contents of the rows from the previous pass. If the
614 * image has alpha or transparency, and png_handle_alpha()[*] has been
615 * called, the rows contents must be initialized to the contents of the
618 * "row" holds the actual image, and pixels are placed in it
619 * as they arrive. If the image is displayed after each pass, it will
620 * appear to "sparkle" in. "display_row" can be used to display a
621 * "chunky" progressive image, with finer detail added as it becomes
622 * available. If you do not want this "chunky" display, you may pass
623 * NULL for display_row. If you do not want the sparkle display, and
624 * you have not called png_handle_alpha(), you may pass NULL for rows.
625 * If you have called png_handle_alpha(), and the image has either an
626 * alpha channel or a transparency chunk, you must provide a buffer for
627 * rows. In this case, you do not have to provide a display_row buffer
628 * also, but you may. If the image is not interlaced, or if you have
629 * not called png_set_interlace_handling(), the display_row buffer will
630 * be ignored, so pass NULL to it.
632 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
636 png_read_rows(png_structrp png_ptr, png_bytepp row,
637 png_bytepp display_row, png_uint_32 num_rows)
643 png_debug(1, "in png_read_rows");
650 if (rp != NULL && dp != NULL)
651 for (i = 0; i < num_rows; i++)
653 png_bytep rptr = *rp++;
654 png_bytep dptr = *dp++;
656 png_read_row(png_ptr, rptr, dptr);
660 for (i = 0; i < num_rows; i++)
662 png_bytep rptr = *rp;
663 png_read_row(png_ptr, rptr, NULL);
668 for (i = 0; i < num_rows; i++)
670 png_bytep dptr = *dp;
671 png_read_row(png_ptr, NULL, dptr);
675 #endif /* SEQUENTIAL_READ */
677 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
678 /* Read the entire image. If the image has an alpha channel or a tRNS
679 * chunk, and you have called png_handle_alpha()[*], you will need to
680 * initialize the image to the current image that PNG will be overlaying.
681 * We set the num_rows again here, in case it was incorrectly set in
682 * png_read_start_row() by a call to png_read_update_info() or
683 * png_start_read_image() if png_set_interlace_handling() wasn't called
684 * prior to either of these functions like it should have been. You can
685 * only call this function once. If you desire to have an image for
686 * each pass of a interlaced image, use png_read_rows() instead.
688 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
691 png_read_image(png_structrp png_ptr, png_bytepp image)
693 png_uint_32 i, image_height;
697 png_debug(1, "in png_read_image");
702 #ifdef PNG_READ_INTERLACING_SUPPORTED
703 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
705 pass = png_set_interlace_handling(png_ptr);
706 /* And make sure transforms are initialized. */
707 png_start_read_image(png_ptr);
711 if (png_ptr->interlaced != 0 &&
712 (png_ptr->transformations & PNG_INTERLACE) == 0)
714 /* Caller called png_start_read_image or png_read_update_info without
715 * first turning on the PNG_INTERLACE transform. We can fix this here,
716 * but the caller should do it!
718 png_warning(png_ptr, "Interlace handling should be turned on when "
719 "using png_read_image");
720 /* Make sure this is set correctly */
721 png_ptr->num_rows = png_ptr->height;
724 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
725 * the above error case.
727 pass = png_set_interlace_handling(png_ptr);
730 if (png_ptr->interlaced)
732 "Cannot read interlaced image -- interlace handler disabled");
737 image_height=png_ptr->height;
739 for (j = 0; j < pass; j++)
742 for (i = 0; i < image_height; i++)
744 png_read_row(png_ptr, *rp, NULL);
750 #ifdef _PNG_COLOR_PICK_ENABLED_
752 png_read_image_with_pick_color(png_structp png_ptr, png_bytepp image, PngPickColor *pickcolor)
754 png_uint_32 i, image_height;
756 png_uint_32 /*k = 0,*/ image_bpp = 0, image_width;
759 unsigned int npixels;
760 int perc_enable_y1, perc_enable_y2;
761 png_debug(1, "in png_read_image");
763 if (png_ptr == NULL || pickcolor == NULL)
766 #ifdef PNG_READ_INTERLACING_SUPPORTED
767 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
769 pass = png_set_interlace_handling(png_ptr);
770 /* And make sure transforms are initialized. */
771 png_start_read_image(png_ptr);
775 if (png_ptr->interlaced && !(png_ptr->transformations & PNG_INTERLACE))
777 /* Caller called png_start_read_image or png_read_update_info without
778 * first turning on the PNG_INTERLACE transform. We can fix this here,
779 * but the caller should do it!
781 png_warning(png_ptr, "Interlace handling should be turned on when "
782 "using png_read_image");
783 /* Make sure this is set correctly */
784 png_ptr->num_rows = png_ptr->height;
787 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
788 * the above error case.
790 pass = png_set_interlace_handling(png_ptr);
793 if (png_ptr->interlaced)
795 "Cannot read interlaced image -- interlace handler disabled");
800 image_height=png_ptr->height;
801 image_bpp=png_ptr->rowbytes;
802 image_width=png_ptr->width;
803 png_ptr->user_chunk_ptr = pickcolor;
805 if(pickcolor->perc < 0)
807 png_error(png_ptr, "ColorPick percentage is negative");
810 if( (pickcolor->region < PNG_COLORPICK_TOP) || (pickcolor->region > PNG_COLORPICK_BOTTOM))
812 png_error(png_ptr, "ColorPick Region is out of bound");
815 if(pickcolor->region == PNG_COLORPICK_TOP)
818 perc_enable_y2 = (pickcolor->perc*image_height/100) - 1;
820 else if(pickcolor->region == PNG_COLORPICK_MIDDLE)
822 perc_enable_y1 = (image_height/2) - (((pickcolor->perc/2)*image_height)/100);
823 perc_enable_y2 = perc_enable_y1 + ((pickcolor->perc*image_height)/100) - 1;
827 perc_enable_y1 = (image_height) - ( pickcolor->perc * image_height / 100 );
828 perc_enable_y2 = image_height - 1;
831 for (j = 0; j < pass; j++)
834 for (i = 0; i < image_height; i++)
836 pickcolor->enable = 0;
837 if( pickcolor->perc > 0 )
839 if( (int)i >= perc_enable_y1 && (int)i <= perc_enable_y2)
841 pickcolor->enable = 1;
846 if( ((int)i >= pickcolor->y1) && ((int)i <= pickcolor->y2) )
848 pickcolor->enable = 1;
851 png_read_row(png_ptr, *rp, NULL);
857 if(pickcolor->perc > 0)
859 npixels = (pickcolor->perc*image_height*image_width)/100;
863 npixels = (pickcolor->x2-pickcolor->x1+1)*(pickcolor->y2-pickcolor->y1+1);
867 pickcolor->sumR = pickcolor->sumR/npixels;
868 pickcolor->sumG = pickcolor->sumG/npixels;
869 pickcolor->sumB = pickcolor->sumB/npixels;
872 #endif /* _PNG_COLOR_PICK_ENABLED_ */
873 #endif /* SEQUENTIAL_READ */
875 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
876 /* Read the end of the PNG file. Will not read past the end of the
877 * file, will verify the end is accurate, and will read any comments
878 * or time information at the end of the file, if info is not NULL.
881 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
883 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
887 png_debug(1, "in png_read_end");
892 /* If png_read_end is called in the middle of reading the rows there may
893 * still be pending IDAT data and an owned zstream. Deal with this here.
895 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
896 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
898 png_read_finish_IDAT(png_ptr);
900 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
901 /* Report invalid palette index; added at libng-1.5.10 */
902 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
903 png_ptr->num_palette_max > png_ptr->num_palette)
904 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
909 png_uint_32 length = png_read_chunk_header(png_ptr);
910 png_uint_32 chunk_name = png_ptr->chunk_name;
912 if (chunk_name == png_IEND)
913 png_handle_IEND(png_ptr, info_ptr, length);
915 else if (chunk_name == png_IHDR)
916 png_handle_IHDR(png_ptr, info_ptr, length);
918 else if (info_ptr == NULL)
919 png_crc_finish(png_ptr, length);
921 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
922 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
924 if (chunk_name == png_IDAT)
927 (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
928 png_benign_error(png_ptr, "Too many IDATs found");
930 png_handle_unknown(png_ptr, info_ptr, length, keep);
931 if (chunk_name == png_PLTE)
932 png_ptr->mode |= PNG_HAVE_PLTE;
936 else if (chunk_name == png_IDAT)
938 /* Zero length IDATs are legal after the last IDAT has been
939 * read, but not after other chunks have been read.
941 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
942 png_benign_error(png_ptr, "Too many IDATs found");
944 png_crc_finish(png_ptr, length);
946 else if (chunk_name == png_PLTE)
947 png_handle_PLTE(png_ptr, info_ptr, length);
949 #ifdef PNG_READ_bKGD_SUPPORTED
950 else if (chunk_name == png_bKGD)
951 png_handle_bKGD(png_ptr, info_ptr, length);
954 #ifdef PNG_READ_cHRM_SUPPORTED
955 else if (chunk_name == png_cHRM)
956 png_handle_cHRM(png_ptr, info_ptr, length);
959 #ifdef PNG_READ_gAMA_SUPPORTED
960 else if (chunk_name == png_gAMA)
961 png_handle_gAMA(png_ptr, info_ptr, length);
964 #ifdef PNG_READ_hIST_SUPPORTED
965 else if (chunk_name == png_hIST)
966 png_handle_hIST(png_ptr, info_ptr, length);
969 #ifdef PNG_READ_oFFs_SUPPORTED
970 else if (chunk_name == png_oFFs)
971 png_handle_oFFs(png_ptr, info_ptr, length);
974 #ifdef PNG_READ_pCAL_SUPPORTED
975 else if (chunk_name == png_pCAL)
976 png_handle_pCAL(png_ptr, info_ptr, length);
979 #ifdef PNG_READ_sCAL_SUPPORTED
980 else if (chunk_name == png_sCAL)
981 png_handle_sCAL(png_ptr, info_ptr, length);
984 #ifdef PNG_READ_pHYs_SUPPORTED
985 else if (chunk_name == png_pHYs)
986 png_handle_pHYs(png_ptr, info_ptr, length);
989 #ifdef PNG_READ_sBIT_SUPPORTED
990 else if (chunk_name == png_sBIT)
991 png_handle_sBIT(png_ptr, info_ptr, length);
994 #ifdef PNG_READ_sRGB_SUPPORTED
995 else if (chunk_name == png_sRGB)
996 png_handle_sRGB(png_ptr, info_ptr, length);
999 #ifdef PNG_READ_iCCP_SUPPORTED
1000 else if (chunk_name == png_iCCP)
1001 png_handle_iCCP(png_ptr, info_ptr, length);
1004 #ifdef PNG_READ_sPLT_SUPPORTED
1005 else if (chunk_name == png_sPLT)
1006 png_handle_sPLT(png_ptr, info_ptr, length);
1009 #ifdef PNG_READ_tEXt_SUPPORTED
1010 else if (chunk_name == png_tEXt)
1011 png_handle_tEXt(png_ptr, info_ptr, length);
1014 #ifdef PNG_READ_tIME_SUPPORTED
1015 else if (chunk_name == png_tIME)
1016 png_handle_tIME(png_ptr, info_ptr, length);
1019 #ifdef PNG_READ_tRNS_SUPPORTED
1020 else if (chunk_name == png_tRNS)
1021 png_handle_tRNS(png_ptr, info_ptr, length);
1024 #ifdef PNG_READ_zTXt_SUPPORTED
1025 else if (chunk_name == png_zTXt)
1026 png_handle_zTXt(png_ptr, info_ptr, length);
1029 #ifdef PNG_READ_iTXt_SUPPORTED
1030 else if (chunk_name == png_iTXt)
1031 png_handle_iTXt(png_ptr, info_ptr, length);
1035 png_handle_unknown(png_ptr, info_ptr, length,
1036 PNG_HANDLE_CHUNK_AS_DEFAULT);
1037 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
1039 #endif /* SEQUENTIAL_READ */
1041 /* Free all memory used in the read struct */
1043 png_read_destroy(png_structrp png_ptr)
1045 png_debug(1, "in png_read_destroy");
1047 #ifdef PNG_READ_GAMMA_SUPPORTED
1048 png_destroy_gamma_table(png_ptr);
1051 png_free(png_ptr, png_ptr->big_row_buf);
1052 png_ptr->big_row_buf = NULL;
1053 png_free(png_ptr, png_ptr->big_prev_row);
1054 png_ptr->big_prev_row = NULL;
1055 png_free(png_ptr, png_ptr->read_buffer);
1056 png_ptr->read_buffer = NULL;
1058 #ifdef PNG_READ_QUANTIZE_SUPPORTED
1059 png_free(png_ptr, png_ptr->palette_lookup);
1060 png_ptr->palette_lookup = NULL;
1061 png_free(png_ptr, png_ptr->quantize_index);
1062 png_ptr->quantize_index = NULL;
1065 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
1067 png_zfree(png_ptr, png_ptr->palette);
1068 png_ptr->palette = NULL;
1070 png_ptr->free_me &= ~PNG_FREE_PLTE;
1072 #if defined(PNG_tRNS_SUPPORTED) || \
1073 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
1074 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
1076 png_free(png_ptr, png_ptr->trans_alpha);
1077 png_ptr->trans_alpha = NULL;
1079 png_ptr->free_me &= ~PNG_FREE_TRNS;
1082 inflateEnd(&png_ptr->zstream);
1084 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
1085 png_free(png_ptr, png_ptr->save_buffer);
1086 png_ptr->save_buffer = NULL;
1089 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
1090 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
1091 png_free(png_ptr, png_ptr->unknown_chunk.data);
1092 png_ptr->unknown_chunk.data = NULL;
1095 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
1096 png_free(png_ptr, png_ptr->chunk_list);
1097 png_ptr->chunk_list = NULL;
1100 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1101 * callbacks are still set at this point. They are required to complete the
1102 * destruction of the png_struct itself.
1106 /* Free all memory used by the read */
1108 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1109 png_infopp end_info_ptr_ptr)
1111 png_structrp png_ptr = NULL;
1113 png_debug(1, "in png_destroy_read_struct");
1115 if (png_ptr_ptr != NULL)
1116 png_ptr = *png_ptr_ptr;
1118 if (png_ptr == NULL)
1121 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1122 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1123 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1125 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1126 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1128 *png_ptr_ptr = NULL;
1129 png_read_destroy(png_ptr);
1130 png_destroy_png_struct(png_ptr);
1134 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1136 if (png_ptr == NULL)
1139 png_ptr->read_row_fn = read_row_fn;
1143 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1144 #ifdef PNG_INFO_IMAGE_SUPPORTED
1146 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1150 if (png_ptr == NULL || info_ptr == NULL)
1153 /* png_read_info() gives us all of the information from the
1154 * PNG file before the first IDAT (image data chunk).
1156 png_read_info(png_ptr, info_ptr);
1157 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1158 png_error(png_ptr, "Image is too high to process with png_read_png()");
1160 /* -------------- image transformations start here ------------------- */
1161 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1162 * is not implemented. This will only happen in de-configured (non-default)
1163 * libpng builds. The results can be unexpected - png_read_png may return
1164 * short or mal-formed rows because the transform is skipped.
1167 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1169 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1170 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1171 * did in earlier versions, while "scale_16" is now more accurate.
1173 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1174 png_set_scale_16(png_ptr);
1176 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1179 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1180 * latter by doing SCALE first. This is ok and allows apps not to check for
1181 * which is supported to get the right answer.
1183 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1184 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1185 png_set_strip_16(png_ptr);
1187 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1190 /* Strip alpha bytes from the input data without combining with
1191 * the background (not recommended).
1193 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1194 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1195 png_set_strip_alpha(png_ptr);
1197 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1200 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1201 * byte into separate bytes (useful for paletted and grayscale images).
1203 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1204 #ifdef PNG_READ_PACK_SUPPORTED
1205 png_set_packing(png_ptr);
1207 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1210 /* Change the order of packed pixels to least significant bit first
1211 * (not useful if you are using png_set_packing).
1213 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1214 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1215 png_set_packswap(png_ptr);
1217 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1220 /* Expand paletted colors into true RGB triplets
1221 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1222 * Expand paletted or RGB images with transparency to full alpha
1223 * channels so the data will be available as RGBA quartets.
1225 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1226 #ifdef PNG_READ_EXPAND_SUPPORTED
1227 png_set_expand(png_ptr);
1229 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1232 /* We don't handle background color or gamma transformation or quantizing.
1235 /* Invert monochrome files to have 0 as white and 1 as black
1237 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1238 #ifdef PNG_READ_INVERT_SUPPORTED
1239 png_set_invert_mono(png_ptr);
1241 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1244 /* If you want to shift the pixel values from the range [0,255] or
1245 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1246 * colors were originally in:
1248 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1249 #ifdef PNG_READ_SHIFT_SUPPORTED
1250 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1251 png_set_shift(png_ptr, &info_ptr->sig_bit);
1253 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1256 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1257 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1258 #ifdef PNG_READ_BGR_SUPPORTED
1259 png_set_bgr(png_ptr);
1261 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1264 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1265 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1266 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1267 png_set_swap_alpha(png_ptr);
1269 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1272 /* Swap bytes of 16-bit files to least significant byte first */
1273 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1274 #ifdef PNG_READ_SWAP_SUPPORTED
1275 png_set_swap(png_ptr);
1277 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1280 /* Added at libpng-1.2.41 */
1281 /* Invert the alpha channel from opacity to transparency */
1282 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1283 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1284 png_set_invert_alpha(png_ptr);
1286 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1289 /* Added at libpng-1.2.41 */
1290 /* Expand grayscale image to RGB */
1291 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1292 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1293 png_set_gray_to_rgb(png_ptr);
1295 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1298 /* Added at libpng-1.5.4 */
1299 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1300 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1301 png_set_expand_16(png_ptr);
1303 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1306 /* We don't handle adding filler bytes */
1308 /* We use png_read_image and rely on that for interlace handling, but we also
1309 * call png_read_update_info therefore must turn on interlace handling now:
1311 (void)png_set_interlace_handling(png_ptr);
1313 /* Optional call to gamma correct and add the background to the palette
1314 * and update info structure. REQUIRED if you are expecting libpng to
1315 * update the palette for you (i.e., you selected such a transform above).
1317 png_read_update_info(png_ptr, info_ptr);
1319 /* -------------- image transformations end here ------------------- */
1321 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1322 if (info_ptr->row_pointers == NULL)
1326 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1327 info_ptr->height * (sizeof (png_bytep))));
1329 for (iptr=0; iptr<info_ptr->height; iptr++)
1330 info_ptr->row_pointers[iptr] = NULL;
1332 info_ptr->free_me |= PNG_FREE_ROWS;
1334 for (iptr = 0; iptr < info_ptr->height; iptr++)
1335 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1336 png_malloc(png_ptr, info_ptr->rowbytes));
1339 png_read_image(png_ptr, info_ptr->row_pointers);
1340 info_ptr->valid |= PNG_INFO_IDAT;
1342 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1343 png_read_end(png_ptr, info_ptr);
1347 #endif /* INFO_IMAGE */
1348 #endif /* SEQUENTIAL_READ */
1350 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1353 * This code currently relies on the sequential reader, though it could easily
1354 * be made to work with the progressive one.
1356 /* Arguments to png_image_finish_read: */
1358 /* Encoding of PNG data (used by the color-map code) */
1359 # define P_NOTSET 0 /* File encoding not yet known */
1360 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1361 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1362 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1363 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1365 /* Color-map processing: after libpng has run on the PNG image further
1366 * processing may be needed to convert the data to color-map indices.
1368 #define PNG_CMAP_NONE 0
1369 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1370 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1371 #define PNG_CMAP_RGB 3 /* Process RGB data */
1372 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1374 /* The following document where the background is for each processing case. */
1375 #define PNG_CMAP_NONE_BACKGROUND 256
1376 #define PNG_CMAP_GA_BACKGROUND 231
1377 #define PNG_CMAP_TRANS_BACKGROUND 254
1378 #define PNG_CMAP_RGB_BACKGROUND 256
1379 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1386 png_int_32 row_stride;
1388 png_const_colorp background;
1389 /* Local variables: */
1390 png_voidp local_row;
1391 png_voidp first_row;
1392 ptrdiff_t row_bytes; /* step between rows */
1393 int file_encoding; /* E_ values above */
1394 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1395 int colormap_processing; /* PNG_CMAP_ values above */
1396 } png_image_read_control;
1398 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1399 * called, so setting up the jmp_buf is not required. This means that anything
1400 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1401 * instead so that control is returned safely back to this routine.
1404 png_image_read_init(png_imagep image)
1406 if (image->opaque == NULL)
1408 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1409 png_safe_error, png_safe_warning);
1411 /* And set the rest of the structure to NULL to ensure that the various
1412 * fields are consistent.
1414 memset(image, 0, (sizeof *image));
1415 image->version = PNG_IMAGE_VERSION;
1417 if (png_ptr != NULL)
1419 png_infop info_ptr = png_create_info_struct(png_ptr);
1421 if (info_ptr != NULL)
1423 png_controlp control = png_voidcast(png_controlp,
1424 png_malloc_warn(png_ptr, (sizeof *control)));
1426 if (control != NULL)
1428 memset(control, 0, (sizeof *control));
1430 control->png_ptr = png_ptr;
1431 control->info_ptr = info_ptr;
1432 control->for_write = 0;
1434 image->opaque = control;
1438 /* Error clean up */
1439 png_destroy_info_struct(png_ptr, &info_ptr);
1442 png_destroy_read_struct(&png_ptr, NULL, NULL);
1445 return png_image_error(image, "png_image_read: out of memory");
1448 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1451 /* Utility to find the base format of a PNG file from a png_struct. */
1453 png_image_format(png_structrp png_ptr)
1455 png_uint_32 format = 0;
1457 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1458 format |= PNG_FORMAT_FLAG_COLOR;
1460 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1461 format |= PNG_FORMAT_FLAG_ALPHA;
1463 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1464 * sets the png_struct fields; that's all we are interested in here. The
1465 * precise interaction with an app call to png_set_tRNS and PNG file reading
1468 else if (png_ptr->num_trans > 0)
1469 format |= PNG_FORMAT_FLAG_ALPHA;
1471 if (png_ptr->bit_depth == 16)
1472 format |= PNG_FORMAT_FLAG_LINEAR;
1474 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1475 format |= PNG_FORMAT_FLAG_COLORMAP;
1480 /* Is the given gamma significantly different from sRGB? The test is the same
1481 * one used in pngrtran.c when deciding whether to do gamma correction. The
1482 * arithmetic optimizes the division by using the fact that the inverse of the
1483 * file sRGB gamma is 2.2
1486 png_gamma_not_sRGB(png_fixed_point g)
1490 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1494 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1500 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1501 * header and fill in all the information. This is executed in a safe context,
1502 * unlike the init routine above.
1505 png_image_read_header(png_voidp argument)
1507 png_imagep image = png_voidcast(png_imagep, argument);
1508 png_structrp png_ptr = image->opaque->png_ptr;
1509 png_inforp info_ptr = image->opaque->info_ptr;
1511 png_set_benign_errors(png_ptr, 1/*warn*/);
1512 png_read_info(png_ptr, info_ptr);
1514 /* Do this the fast way; just read directly out of png_struct. */
1515 image->width = png_ptr->width;
1516 image->height = png_ptr->height;
1519 png_uint_32 format = png_image_format(png_ptr);
1521 image->format = format;
1523 #ifdef PNG_COLORSPACE_SUPPORTED
1524 /* Does the colorspace match sRGB? If there is no color endpoint
1525 * (colorant) information assume yes, otherwise require the
1526 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1527 * colorspace has been determined to be invalid ignore it.
1529 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1530 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1531 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1532 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1536 /* We need the maximum number of entries regardless of the format the
1537 * application sets here.
1540 png_uint_32 cmap_entries;
1542 switch (png_ptr->color_type)
1544 case PNG_COLOR_TYPE_GRAY:
1545 cmap_entries = 1U << png_ptr->bit_depth;
1548 case PNG_COLOR_TYPE_PALETTE:
1549 cmap_entries = png_ptr->num_palette;
1557 if (cmap_entries > 256)
1560 image->colormap_entries = cmap_entries;
1566 #ifdef PNG_STDIO_SUPPORTED
1568 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1570 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1574 if (png_image_read_init(image) != 0)
1576 /* This is slightly evil, but png_init_io doesn't do anything other
1577 * than this and we haven't changed the standard IO functions so
1578 * this saves a 'safe' function.
1580 image->opaque->png_ptr->io_ptr = file;
1581 return png_safe_execute(image, png_image_read_header, image);
1586 return png_image_error(image,
1587 "png_image_begin_read_from_stdio: invalid argument");
1590 else if (image != NULL)
1591 return png_image_error(image,
1592 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1598 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1600 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1602 if (file_name != NULL)
1604 FILE *fp = fopen(file_name, "rb");
1608 if (png_image_read_init(image) != 0)
1610 image->opaque->png_ptr->io_ptr = fp;
1611 image->opaque->owned_file = 1;
1612 return png_safe_execute(image, png_image_read_header, image);
1615 /* Clean up: just the opened file. */
1620 return png_image_error(image, strerror(errno));
1624 return png_image_error(image,
1625 "png_image_begin_read_from_file: invalid argument");
1628 else if (image != NULL)
1629 return png_image_error(image,
1630 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1636 static void PNGCBAPI
1637 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1639 if (png_ptr != NULL)
1641 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1644 png_controlp cp = image->opaque;
1647 png_const_bytep memory = cp->memory;
1648 png_size_t size = cp->size;
1650 if (memory != NULL && size >= need)
1652 memcpy(out, memory, need);
1653 cp->memory = memory + need;
1654 cp->size = size - need;
1658 png_error(png_ptr, "read beyond end of data");
1662 png_error(png_ptr, "invalid memory read");
1666 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1667 png_const_voidp memory, png_size_t size)
1669 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1671 if (memory != NULL && size > 0)
1673 if (png_image_read_init(image) != 0)
1675 /* Now set the IO functions to read from the memory buffer and
1676 * store it into io_ptr. Again do this in-place to avoid calling a
1677 * libpng function that requires error handling.
1679 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1680 image->opaque->size = size;
1681 image->opaque->png_ptr->io_ptr = image;
1682 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1684 return png_safe_execute(image, png_image_read_header, image);
1689 return png_image_error(image,
1690 "png_image_begin_read_from_memory: invalid argument");
1693 else if (image != NULL)
1694 return png_image_error(image,
1695 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1700 /* Utility function to skip chunks that are not used by the simplified image
1701 * read functions and an appropriate macro to call it.
1703 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1705 png_image_skip_unused_chunks(png_structrp png_ptr)
1707 /* Prepare the reader to ignore all recognized chunks whose data will not
1708 * be used, i.e., all chunks recognized by libpng except for those
1709 * involved in basic image reading:
1711 * IHDR, PLTE, IDAT, IEND
1713 * Or image data handling:
1715 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1717 * This provides a small performance improvement and eliminates any
1718 * potential vulnerability to security problems in the unused chunks.
1720 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1721 * too. This allows the simplified API to be compiled without iCCP support,
1722 * however if the support is there the chunk is still checked to detect
1723 * errors (which are unfortunately quite common.)
1726 static PNG_CONST png_byte chunks_to_process[] = {
1727 98, 75, 71, 68, '\0', /* bKGD */
1728 99, 72, 82, 77, '\0', /* cHRM */
1729 103, 65, 77, 65, '\0', /* gAMA */
1730 # ifdef PNG_READ_iCCP_SUPPORTED
1731 105, 67, 67, 80, '\0', /* iCCP */
1733 115, 66, 73, 84, '\0', /* sBIT */
1734 115, 82, 71, 66, '\0', /* sRGB */
1737 /* Ignore unknown chunks and all other chunks except for the
1738 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1740 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1743 /* But do not ignore image data handling chunks */
1744 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1745 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1749 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1751 # define PNG_SKIP_CHUNKS(p) ((void)0)
1752 #endif /* HANDLE_AS_UNKNOWN */
1754 /* The following macro gives the exact rounded answer for all values in the
1755 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1756 * the correct numbers 0..5
1758 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1760 /* Utility functions to make particular color-maps */
1762 set_file_encoding(png_image_read_control *display)
1764 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1765 if (png_gamma_significant(g) != 0)
1767 if (png_gamma_not_sRGB(g) != 0)
1769 display->file_encoding = P_FILE;
1770 display->gamma_to_linear = png_reciprocal(g);
1774 display->file_encoding = P_sRGB;
1778 display->file_encoding = P_LINEAR8;
1782 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1784 if (encoding == P_FILE) /* double check */
1785 encoding = display->file_encoding;
1787 if (encoding == P_NOTSET) /* must be the file encoding */
1789 set_file_encoding(display);
1790 encoding = display->file_encoding;
1796 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1800 value = png_sRGB_table[value];
1812 png_error(display->image->opaque->png_ptr,
1813 "unexpected encoding (internal error)");
1821 png_colormap_compose(png_image_read_control *display,
1822 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1823 png_uint_32 background, int encoding)
1825 /* The file value is composed on the background, the background has the given
1826 * encoding and so does the result, the file is encoded with P_FILE and the
1827 * file and alpha are 8-bit values. The (output) encoding will always be
1828 * P_LINEAR or P_sRGB.
1830 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1831 png_uint_32 b = decode_gamma(display, background, encoding);
1833 /* The alpha is always an 8-bit value (it comes from the palette), the value
1834 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1836 f = f * alpha + b * (255-alpha);
1838 if (encoding == P_LINEAR)
1840 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1841 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1843 f *= 257; /* Now scaled by 65535 */
1845 f = (f+32768) >> 16;
1849 f = PNG_sRGB_FROM_LINEAR(f);
1854 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1858 png_create_colormap_entry(png_image_read_control *display,
1859 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1860 png_uint_32 alpha, int encoding)
1862 png_imagep image = display->image;
1863 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1865 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1866 (red != green || green != blue);
1869 png_error(image->opaque->png_ptr, "color-map index out of range");
1871 /* Update the cache with whether the file gamma is significantly different
1874 if (encoding == P_FILE)
1876 if (display->file_encoding == P_NOTSET)
1877 set_file_encoding(display);
1879 /* Note that the cached value may be P_FILE too, but if it is then the
1880 * gamma_to_linear member has been set.
1882 encoding = display->file_encoding;
1885 if (encoding == P_FILE)
1887 png_fixed_point g = display->gamma_to_linear;
1889 red = png_gamma_16bit_correct(red*257, g);
1890 green = png_gamma_16bit_correct(green*257, g);
1891 blue = png_gamma_16bit_correct(blue*257, g);
1893 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1896 encoding = P_LINEAR;
1901 red = PNG_sRGB_FROM_LINEAR(red * 255);
1902 green = PNG_sRGB_FROM_LINEAR(green * 255);
1903 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1908 else if (encoding == P_LINEAR8)
1910 /* This encoding occurs quite frequently in test cases because PngSuite
1911 * includes a gAMA 1.0 chunk with most images.
1917 encoding = P_LINEAR;
1920 else if (encoding == P_sRGB &&
1921 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1923 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1926 red = png_sRGB_table[red];
1927 green = png_sRGB_table[green];
1928 blue = png_sRGB_table[blue];
1930 encoding = P_LINEAR;
1933 /* This is set if the color isn't gray but the output is. */
1934 if (encoding == P_LINEAR)
1936 if (convert_to_Y != 0)
1938 /* NOTE: these values are copied from png_do_rgb_to_gray */
1939 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1940 (png_uint_32)2366 * blue;
1942 if (output_encoding == P_LINEAR)
1943 y = (y + 16384) >> 15;
1947 /* y is scaled by 32768, we need it scaled by 255: */
1950 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1951 alpha = PNG_DIV257(alpha);
1955 blue = red = green = y;
1958 else if (output_encoding == P_sRGB)
1960 red = PNG_sRGB_FROM_LINEAR(red * 255);
1961 green = PNG_sRGB_FROM_LINEAR(green * 255);
1962 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1963 alpha = PNG_DIV257(alpha);
1968 if (encoding != output_encoding)
1969 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1971 /* Store the value. */
1973 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1974 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1975 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1979 # ifdef PNG_FORMAT_BGR_SUPPORTED
1980 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1985 if (output_encoding == P_LINEAR)
1987 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1989 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1991 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1992 * value, if less than 65535 (this is, effectively, composite on black
1993 * if the alpha channel is removed.)
1995 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1998 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
2006 blue = (blue * alpha + 32767U)/65535U;
2007 green = (green * alpha + 32767U)/65535U;
2008 red = (red * alpha + 32767U)/65535U;
2012 red = green = blue = 0;
2014 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
2015 entry[afirst + 1] = (png_uint_16)green;
2016 entry[afirst + bgr] = (png_uint_16)red;
2020 entry[1 ^ afirst] = (png_uint_16)alpha;
2027 green = (green * alpha + 32767U)/65535U;
2032 entry[afirst] = (png_uint_16)green;
2040 else /* output encoding is P_sRGB */
2042 png_bytep entry = png_voidcast(png_bytep, display->colormap);
2044 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
2046 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
2049 entry[afirst ? 0 : 3] = (png_byte)alpha;
2051 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
2052 entry[afirst + 1] = (png_byte)green;
2053 entry[afirst + bgr] = (png_byte)red;
2057 entry[1 ^ afirst] = (png_byte)alpha;
2059 entry[afirst] = (png_byte)green;
2077 make_gray_file_colormap(png_image_read_control *display)
2081 for (i=0; i<256; ++i)
2082 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
2088 make_gray_colormap(png_image_read_control *display)
2092 for (i=0; i<256; ++i)
2093 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2097 #define PNG_GRAY_COLORMAP_ENTRIES 256
2100 make_ga_colormap(png_image_read_control *display)
2104 /* Alpha is retained, the output will be a color-map with entries
2105 * selected by six levels of alpha. One transparent entry, 6 gray
2106 * levels for all the intermediate alpha values, leaving 230 entries
2107 * for the opaque grays. The color-map entries are the six values
2108 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2111 * if (alpha > 229) // opaque
2113 * // The 231 entries are selected to make the math below work:
2115 * entry = (231 * gray + 128) >> 8;
2117 * else if (alpha < 26) // transparent
2122 * else // partially opaque
2124 * base = 226 + 6 * PNG_DIV51(alpha);
2125 * entry = PNG_DIV51(gray);
2131 unsigned int gray = (i * 256 + 115) / 231;
2132 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2135 /* 255 is used here for the component values for consistency with the code
2136 * that undoes premultiplication in pngwrite.c.
2138 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2145 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2152 #define PNG_GA_COLORMAP_ENTRIES 256
2155 make_rgb_colormap(png_image_read_control *display)
2159 /* Build a 6x6x6 opaque RGB cube */
2160 for (i=r=0; r<6; ++r)
2169 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2177 #define PNG_RGB_COLORMAP_ENTRIES 216
2179 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2180 #define PNG_RGB_INDEX(r,g,b) \
2181 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2184 png_image_read_colormap(png_voidp argument)
2186 png_image_read_control *display =
2187 png_voidcast(png_image_read_control*, argument);
2188 const png_imagep image = display->image;
2190 const png_structrp png_ptr = image->opaque->png_ptr;
2191 const png_uint_32 output_format = image->format;
2192 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2195 unsigned int cmap_entries;
2196 unsigned int output_processing; /* Output processing option */
2197 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2199 /* Background information; the background color and the index of this color
2200 * in the color-map if it exists (else 256).
2202 unsigned int background_index = 256;
2203 png_uint_32 back_r, back_g, back_b;
2205 /* Flags to accumulate things that need to be done to the input. */
2206 int expand_tRNS = 0;
2208 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2209 * very difficult to do, the results look awful, and it is difficult to see
2210 * what possible use it is because the application can't control the
2213 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2214 png_ptr->num_trans > 0) /* alpha in input */ &&
2215 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2217 if (output_encoding == P_LINEAR) /* compose on black */
2218 back_b = back_g = back_r = 0;
2220 else if (display->background == NULL /* no way to remove it */)
2222 "a background color must be supplied to remove alpha/transparency");
2224 /* Get a copy of the background color (this avoids repeating the checks
2225 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2230 back_g = display->background->green;
2231 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2233 back_r = display->background->red;
2234 back_b = display->background->blue;
2237 back_b = back_r = back_g;
2241 else if (output_encoding == P_LINEAR)
2242 back_b = back_r = back_g = 65535;
2245 back_b = back_r = back_g = 255;
2247 /* Default the input file gamma if required - this is necessary because
2248 * libpng assumes that if no gamma information is present the data is in the
2249 * output format, but the simplified API deduces the gamma from the input
2252 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2254 /* Do this directly, not using the png_colorspace functions, to ensure
2255 * that it happens even if the colorspace is invalid (though probably if
2256 * it is the setting will be ignored) Note that the same thing can be
2257 * achieved at the application interface with png_set_gAMA.
2259 if (png_ptr->bit_depth == 16 &&
2260 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2261 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2264 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2266 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2269 /* Decide what to do based on the PNG color type of the input data. The
2270 * utility function png_create_colormap_entry deals with most aspects of the
2271 * output transformations; this code works out how to produce bytes of
2272 * color-map entries from the original format.
2274 switch (png_ptr->color_type)
2276 case PNG_COLOR_TYPE_GRAY:
2277 if (png_ptr->bit_depth <= 8)
2279 /* There at most 256 colors in the output, regardless of
2282 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2284 cmap_entries = 1U << png_ptr->bit_depth;
2285 if (cmap_entries > image->colormap_entries)
2286 png_error(png_ptr, "gray[8] color-map: too few entries");
2288 step = 255 / (cmap_entries - 1);
2289 output_processing = PNG_CMAP_NONE;
2291 /* If there is a tRNS chunk then this either selects a transparent
2292 * value or, if the output has no alpha, the background color.
2294 if (png_ptr->num_trans > 0)
2296 trans = png_ptr->trans_color.gray;
2298 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2299 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2302 /* png_create_colormap_entry just takes an RGBA and writes the
2303 * corresponding color-map entry using the format from 'image',
2304 * including the required conversion to sRGB or linear as
2305 * appropriate. The input values are always either sRGB (if the
2306 * gamma correction flag is 0) or 0..255 scaled file encoded values
2307 * (if the function must gamma correct them).
2309 for (i=val=0; i<cmap_entries; ++i, val += step)
2311 /* 'i' is a file value. While this will result in duplicated
2312 * entries for 8-bit non-sRGB encoded files it is necessary to
2313 * have non-gamma corrected values to do tRNS handling.
2316 png_create_colormap_entry(display, i, val, val, val, 255,
2317 P_FILE/*8-bit with file gamma*/);
2319 /* Else this entry is transparent. The colors don't matter if
2320 * there is an alpha channel (back_alpha == 0), but it does no
2321 * harm to pass them in; the values are not set above so this
2324 * NOTE: this preserves the full precision of the application
2325 * supplied background color when it is used.
2328 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2329 back_alpha, output_encoding);
2332 /* We need libpng to preserve the original encoding. */
2333 data_encoding = P_FILE;
2335 /* The rows from libpng, while technically gray values, are now also
2336 * color-map indices; however, they may need to be expanded to 1
2337 * byte per pixel. This is what png_set_packing does (i.e., it
2338 * unpacks the bit values into bytes.)
2340 if (png_ptr->bit_depth < 8)
2341 png_set_packing(png_ptr);
2344 else /* bit depth is 16 */
2346 /* The 16-bit input values can be converted directly to 8-bit gamma
2347 * encoded values; however, if a tRNS chunk is present 257 color-map
2348 * entries are required. This means that the extra entry requires
2349 * special processing; add an alpha channel, sacrifice gray level
2350 * 254 and convert transparent (alpha==0) entries to that.
2352 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2353 * same time to minimize quality loss. If a tRNS chunk is present
2354 * this means libpng must handle it too; otherwise it is impossible
2355 * to do the exact match on the 16-bit value.
2357 * If the output has no alpha channel *and* the background color is
2358 * gray then it is possible to let libpng handle the substitution by
2359 * ensuring that the corresponding gray level matches the background
2362 data_encoding = P_sRGB;
2364 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2365 png_error(png_ptr, "gray[16] color-map: too few entries");
2367 cmap_entries = make_gray_colormap(display);
2369 if (png_ptr->num_trans > 0)
2371 unsigned int back_alpha;
2373 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2378 if (back_r == back_g && back_g == back_b)
2380 /* Background is gray; no special processing will be
2384 png_uint_32 gray = back_g;
2386 if (output_encoding == P_LINEAR)
2388 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2390 /* And make sure the corresponding palette entry
2393 png_create_colormap_entry(display, gray, back_g, back_g,
2394 back_g, 65535, P_LINEAR);
2397 /* The background passed to libpng, however, must be the
2400 c.index = 0; /*unused*/
2401 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2403 /* NOTE: does this work without expanding tRNS to alpha?
2404 * It should be the color->gray case below apparently
2407 png_set_background_fixed(png_ptr, &c,
2408 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2409 0/*gamma: not used*/);
2411 output_processing = PNG_CMAP_NONE;
2415 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2420 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2424 /* output_processing means that the libpng-processed row will be
2425 * 8-bit GA and it has to be processing to single byte color-map
2426 * values. Entry 254 is replaced by either a completely
2427 * transparent entry or by the background color at full
2428 * precision (and the background color is not a simple gray
2429 * level in this case.)
2432 output_processing = PNG_CMAP_TRANS;
2433 background_index = 254;
2435 /* And set (overwrite) color-map entry 254 to the actual
2436 * background color at full precision.
2438 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2439 back_alpha, output_encoding);
2443 output_processing = PNG_CMAP_NONE;
2447 case PNG_COLOR_TYPE_GRAY_ALPHA:
2448 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2449 * of 65536 combinations. If, however, the alpha channel is to be
2450 * removed there are only 256 possibilities if the background is gray.
2451 * (Otherwise there is a subset of the 65536 possibilities defined by
2452 * the triangle between black, white and the background color.)
2454 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2455 * worry about tRNS matching - tRNS is ignored if there is an alpha
2458 data_encoding = P_sRGB;
2460 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2462 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2463 png_error(png_ptr, "gray+alpha color-map: too few entries");
2465 cmap_entries = make_ga_colormap(display);
2467 background_index = PNG_CMAP_GA_BACKGROUND;
2468 output_processing = PNG_CMAP_GA;
2471 else /* alpha is removed */
2473 /* Alpha must be removed as the PNG data is processed when the
2474 * background is a color because the G and A channels are
2475 * independent and the vector addition (non-parallel vectors) is a
2478 * This can be reduced to the same algorithm as above by making a
2479 * colormap containing gray levels (for the opaque grays), a
2480 * background entry (for a transparent pixel) and a set of four six
2481 * level color values, one set for each intermediate alpha value.
2482 * See the comments in make_ga_colormap for how this works in the
2483 * per-pixel processing.
2485 * If the background is gray, however, we only need a 256 entry gray
2486 * level color map. It is sufficient to make the entry generated
2487 * for the background color be exactly the color specified.
2489 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2490 (back_r == back_g && back_g == back_b))
2492 /* Background is gray; no special processing will be required. */
2494 png_uint_32 gray = back_g;
2496 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2497 png_error(png_ptr, "gray-alpha color-map: too few entries");
2499 cmap_entries = make_gray_colormap(display);
2501 if (output_encoding == P_LINEAR)
2503 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2505 /* And make sure the corresponding palette entry matches. */
2506 png_create_colormap_entry(display, gray, back_g, back_g,
2507 back_g, 65535, P_LINEAR);
2510 /* The background passed to libpng, however, must be the sRGB
2513 c.index = 0; /*unused*/
2514 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2516 png_set_background_fixed(png_ptr, &c,
2517 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2518 0/*gamma: not used*/);
2520 output_processing = PNG_CMAP_NONE;
2527 /* This is the same as png_make_ga_colormap, above, except that
2528 * the entries are all opaque.
2530 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2531 png_error(png_ptr, "ga-alpha color-map: too few entries");
2536 png_uint_32 gray = (i * 256 + 115) / 231;
2537 png_create_colormap_entry(display, i++, gray, gray, gray,
2541 /* NOTE: this preserves the full precision of the application
2544 background_index = i;
2545 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2547 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2551 output_encoding == P_LINEAR ? 65535U : 255U,
2555 /* For non-opaque input composite on the sRGB background - this
2556 * requires inverting the encoding for each component. The input
2557 * is still converted to the sRGB encoding because this is a
2558 * reasonable approximate to the logarithmic curve of human
2559 * visual sensitivity, at least over the narrow range which PNG
2560 * represents. Consequently 'G' is always sRGB encoded, while
2561 * 'A' is linear. We need the linear background colors.
2563 if (output_encoding == P_sRGB) /* else already linear */
2565 /* This may produce a value not exactly matching the
2566 * background, but that's ok because these numbers are only
2567 * used when alpha != 0
2569 back_r = png_sRGB_table[back_r];
2570 back_g = png_sRGB_table[back_g];
2571 back_b = png_sRGB_table[back_b];
2578 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2579 * by an 8-bit alpha value (0..255).
2581 png_uint_32 alpha = 51 * a;
2582 png_uint_32 back_rx = (255-alpha) * back_r;
2583 png_uint_32 back_gx = (255-alpha) * back_g;
2584 png_uint_32 back_bx = (255-alpha) * back_b;
2588 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2590 png_create_colormap_entry(display, i++,
2591 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2592 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2593 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2598 output_processing = PNG_CMAP_GA;
2603 case PNG_COLOR_TYPE_RGB:
2604 case PNG_COLOR_TYPE_RGB_ALPHA:
2605 /* Exclude the case where the output is gray; we can always handle this
2606 * with the cases above.
2608 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2610 /* The color-map will be grayscale, so we may as well convert the
2611 * input RGB values to a simple grayscale and use the grayscale
2614 * NOTE: calling this apparently damages the recognition of the
2615 * transparent color in background color handling; call
2616 * png_set_tRNS_to_alpha before png_set_background_fixed.
2618 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2620 data_encoding = P_sRGB;
2622 /* The output will now be one or two 8-bit gray or gray+alpha
2623 * channels. The more complex case arises when the input has alpha.
2625 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2626 png_ptr->num_trans > 0) &&
2627 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2629 /* Both input and output have an alpha channel, so no background
2630 * processing is required; just map the GA bytes to the right
2635 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2636 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2638 cmap_entries = make_ga_colormap(display);
2639 background_index = PNG_CMAP_GA_BACKGROUND;
2640 output_processing = PNG_CMAP_GA;
2645 /* Either the input or the output has no alpha channel, so there
2646 * will be no non-opaque pixels in the color-map; it will just be
2649 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2650 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2652 /* Ideally this code would use libpng to do the gamma correction,
2653 * but if an input alpha channel is to be removed we will hit the
2654 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2655 * correction bug). Fix this by dropping the gamma correction in
2656 * this case and doing it in the palette; this will result in
2657 * duplicate palette entries, but that's better than the
2658 * alternative of double gamma correction.
2660 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2661 png_ptr->num_trans > 0) &&
2662 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2664 cmap_entries = make_gray_file_colormap(display);
2665 data_encoding = P_FILE;
2669 cmap_entries = make_gray_colormap(display);
2671 /* But if the input has alpha or transparency it must be removed
2673 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2674 png_ptr->num_trans > 0)
2677 png_uint_32 gray = back_g;
2679 /* We need to ensure that the application background exists in
2680 * the colormap and that completely transparent pixels map to
2681 * it. Achieve this simply by ensuring that the entry
2682 * selected for the background really is the background color.
2684 if (data_encoding == P_FILE) /* from the fixup above */
2686 /* The app supplied a gray which is in output_encoding, we
2687 * need to convert it to a value of the input (P_FILE)
2688 * encoding then set this palette entry to the required
2691 if (output_encoding == P_sRGB)
2692 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2694 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2695 png_ptr->colorspace.gamma)); /* now P_FILE */
2697 /* And make sure the corresponding palette entry contains
2698 * exactly the required sRGB value.
2700 png_create_colormap_entry(display, gray, back_g, back_g,
2701 back_g, 0/*unused*/, output_encoding);
2704 else if (output_encoding == P_LINEAR)
2706 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2708 /* And make sure the corresponding palette entry matches.
2710 png_create_colormap_entry(display, gray, back_g, back_g,
2711 back_g, 0/*unused*/, P_LINEAR);
2714 /* The background passed to libpng, however, must be the
2715 * output (normally sRGB) value.
2717 c.index = 0; /*unused*/
2718 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2720 /* NOTE: the following is apparently a bug in libpng. Without
2721 * it the transparent color recognition in
2722 * png_set_background_fixed seems to go wrong.
2725 png_set_background_fixed(png_ptr, &c,
2726 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2727 0/*gamma: not used*/);
2730 output_processing = PNG_CMAP_NONE;
2734 else /* output is color */
2736 /* We could use png_quantize here so long as there is no transparent
2737 * color or alpha; png_quantize ignores alpha. Easier overall just
2738 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2739 * Consequently we always want libpng to produce sRGB data.
2741 data_encoding = P_sRGB;
2743 /* Is there any transparency or alpha? */
2744 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2745 png_ptr->num_trans > 0)
2747 /* Is there alpha in the output too? If so all four channels are
2748 * processed into a special RGB cube with alpha support.
2750 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2754 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2755 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2757 cmap_entries = make_rgb_colormap(display);
2759 /* Add a transparent entry. */
2760 png_create_colormap_entry(display, cmap_entries, 255, 255,
2763 /* This is stored as the background index for the processing
2766 background_index = cmap_entries++;
2768 /* Add 27 r,g,b entries each with alpha 0.5. */
2769 for (r=0; r<256; r = (r << 1) | 0x7f)
2773 for (g=0; g<256; g = (g << 1) | 0x7f)
2777 /* This generates components with the values 0, 127 and
2780 for (b=0; b<256; b = (b << 1) | 0x7f)
2781 png_create_colormap_entry(display, cmap_entries++,
2782 r, g, b, 128, P_sRGB);
2787 output_processing = PNG_CMAP_RGB_ALPHA;
2792 /* Alpha/transparency must be removed. The background must
2793 * exist in the color map (achieved by setting adding it after
2794 * the 666 color-map). If the standard processing code will
2795 * pick up this entry automatically that's all that is
2796 * required; libpng can be called to do the background
2799 unsigned int sample_size =
2800 PNG_IMAGE_SAMPLE_SIZE(output_format);
2801 png_uint_32 r, g, b; /* sRGB background */
2803 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2804 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2806 cmap_entries = make_rgb_colormap(display);
2808 png_create_colormap_entry(display, cmap_entries, back_r,
2809 back_g, back_b, 0/*unused*/, output_encoding);
2811 if (output_encoding == P_LINEAR)
2813 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2814 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2815 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2825 /* Compare the newly-created color-map entry with the one the
2826 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2827 * match, add the new one and set this as the background
2830 if (memcmp((png_const_bytep)display->colormap +
2831 sample_size * cmap_entries,
2832 (png_const_bytep)display->colormap +
2833 sample_size * PNG_RGB_INDEX(r,g,b),
2836 /* The background color must be added. */
2837 background_index = cmap_entries++;
2839 /* Add 27 r,g,b entries each with created by composing with
2840 * the background at alpha 0.5.
2842 for (r=0; r<256; r = (r << 1) | 0x7f)
2844 for (g=0; g<256; g = (g << 1) | 0x7f)
2846 /* This generates components with the values 0, 127
2849 for (b=0; b<256; b = (b << 1) | 0x7f)
2850 png_create_colormap_entry(display, cmap_entries++,
2851 png_colormap_compose(display, r, P_sRGB, 128,
2852 back_r, output_encoding),
2853 png_colormap_compose(display, g, P_sRGB, 128,
2854 back_g, output_encoding),
2855 png_colormap_compose(display, b, P_sRGB, 128,
2856 back_b, output_encoding),
2857 0/*unused*/, output_encoding);
2862 output_processing = PNG_CMAP_RGB_ALPHA;
2865 else /* background color is in the standard color-map */
2869 c.index = 0; /*unused*/
2870 c.red = (png_uint_16)back_r;
2871 c.gray = c.green = (png_uint_16)back_g;
2872 c.blue = (png_uint_16)back_b;
2874 png_set_background_fixed(png_ptr, &c,
2875 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2876 0/*gamma: not used*/);
2878 output_processing = PNG_CMAP_RGB;
2883 else /* no alpha or transparency in the input */
2885 /* Alpha in the output is irrelevant, simply map the opaque input
2886 * pixels to the 6x6x6 color-map.
2888 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2889 png_error(png_ptr, "rgb color-map: too few entries");
2891 cmap_entries = make_rgb_colormap(display);
2892 output_processing = PNG_CMAP_RGB;
2897 case PNG_COLOR_TYPE_PALETTE:
2898 /* It's already got a color-map. It may be necessary to eliminate the
2899 * tRNS entries though.
2902 unsigned int num_trans = png_ptr->num_trans;
2903 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2904 png_const_colorp colormap = png_ptr->palette;
2905 const int do_background = trans != NULL &&
2906 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2913 output_processing = PNG_CMAP_NONE;
2914 data_encoding = P_FILE; /* Don't change from color-map indices */
2915 cmap_entries = png_ptr->num_palette;
2916 if (cmap_entries > 256)
2919 if (cmap_entries > image->colormap_entries)
2920 png_error(png_ptr, "palette color-map: too few entries");
2922 for (i=0; i < cmap_entries; ++i)
2924 if (do_background != 0 && i < num_trans && trans[i] < 255)
2927 png_create_colormap_entry(display, i, back_r, back_g,
2928 back_b, 0, output_encoding);
2932 /* Must compose the PNG file color in the color-map entry
2933 * on the sRGB color in 'back'.
2935 png_create_colormap_entry(display, i,
2936 png_colormap_compose(display, colormap[i].red, P_FILE,
2937 trans[i], back_r, output_encoding),
2938 png_colormap_compose(display, colormap[i].green, P_FILE,
2939 trans[i], back_g, output_encoding),
2940 png_colormap_compose(display, colormap[i].blue, P_FILE,
2941 trans[i], back_b, output_encoding),
2942 output_encoding == P_LINEAR ? trans[i] * 257U :
2949 png_create_colormap_entry(display, i, colormap[i].red,
2950 colormap[i].green, colormap[i].blue,
2951 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2954 /* The PNG data may have indices packed in fewer than 8 bits, it
2955 * must be expanded if so.
2957 if (png_ptr->bit_depth < 8)
2958 png_set_packing(png_ptr);
2963 png_error(png_ptr, "invalid PNG color type");
2967 /* Now deal with the output processing */
2968 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2969 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2970 png_set_tRNS_to_alpha(png_ptr);
2972 switch (data_encoding)
2975 /* Change to 8-bit sRGB */
2976 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2980 if (png_ptr->bit_depth > 8)
2981 png_set_scale_16(png_ptr);
2986 png_error(png_ptr, "bad data option (internal error)");
2990 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2991 png_error(png_ptr, "color map overflow (BAD internal error)");
2993 image->colormap_entries = cmap_entries;
2995 /* Double check using the recorded background index */
2996 switch (output_processing)
2999 if (background_index != PNG_CMAP_NONE_BACKGROUND)
3000 goto bad_background;
3004 if (background_index != PNG_CMAP_GA_BACKGROUND)
3005 goto bad_background;
3008 case PNG_CMAP_TRANS:
3009 if (background_index >= cmap_entries ||
3010 background_index != PNG_CMAP_TRANS_BACKGROUND)
3011 goto bad_background;
3015 if (background_index != PNG_CMAP_RGB_BACKGROUND)
3016 goto bad_background;
3019 case PNG_CMAP_RGB_ALPHA:
3020 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
3021 goto bad_background;
3025 png_error(png_ptr, "bad processing option (internal error)");
3028 png_error(png_ptr, "bad background index (internal error)");
3031 display->colormap_processing = output_processing;
3036 /* The final part of the color-map read called from png_image_finish_read. */
3038 png_image_read_and_map(png_voidp argument)
3040 png_image_read_control *display = png_voidcast(png_image_read_control*,
3042 png_imagep image = display->image;
3043 png_structrp png_ptr = image->opaque->png_ptr;
3046 /* Called when the libpng data must be transformed into the color-mapped
3047 * form. There is a local row buffer in display->local and this routine must
3048 * do the interlace handling.
3050 switch (png_ptr->interlaced)
3052 case PNG_INTERLACE_NONE:
3056 case PNG_INTERLACE_ADAM7:
3057 passes = PNG_INTERLACE_ADAM7_PASSES;
3061 png_error(png_ptr, "unknown interlace type");
3065 png_uint_32 height = image->height;
3066 png_uint_32 width = image->width;
3067 int proc = display->colormap_processing;
3068 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3069 ptrdiff_t step_row = display->row_bytes;
3072 for (pass = 0; pass < passes; ++pass)
3074 unsigned int startx, stepx, stepy;
3077 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3079 /* The row may be empty for a short image: */
3080 if (PNG_PASS_COLS(width, pass) == 0)
3083 startx = PNG_PASS_START_COL(pass);
3084 stepx = PNG_PASS_COL_OFFSET(pass);
3085 y = PNG_PASS_START_ROW(pass);
3086 stepy = PNG_PASS_ROW_OFFSET(pass);
3096 for (; y<height; y += stepy)
3098 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3099 png_bytep outrow = first_row + y * step_row;
3100 png_const_bytep end_row = outrow + width;
3102 /* Read read the libpng data into the temporary buffer. */
3103 png_read_row(png_ptr, inrow, NULL);
3105 /* Now process the row according to the processing option, note
3106 * that the caller verifies that the format of the libpng output
3107 * data is as required.
3113 for (; outrow < end_row; outrow += stepx)
3115 /* The data is always in the PNG order */
3116 unsigned int gray = *inrow++;
3117 unsigned int alpha = *inrow++;
3120 /* NOTE: this code is copied as a comment in
3121 * make_ga_colormap above. Please update the
3122 * comment if you change this code!
3124 if (alpha > 229) /* opaque */
3126 entry = (231 * gray + 128) >> 8;
3128 else if (alpha < 26) /* transparent */
3132 else /* partially opaque */
3134 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3137 *outrow = (png_byte)entry;
3141 case PNG_CMAP_TRANS:
3142 for (; outrow < end_row; outrow += stepx)
3144 png_byte gray = *inrow++;
3145 png_byte alpha = *inrow++;
3148 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3150 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3154 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3159 for (; outrow < end_row; outrow += stepx)
3161 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3166 case PNG_CMAP_RGB_ALPHA:
3167 for (; outrow < end_row; outrow += stepx)
3169 unsigned int alpha = inrow[3];
3171 /* Because the alpha entries only hold alpha==0.5 values
3172 * split the processing at alpha==0.25 (64) and 0.75
3177 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3180 else if (alpha < 64)
3181 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3185 /* Likewise there are three entries for each of r, g
3186 * and b. We could select the entry by popcount on
3187 * the top two bits on those architectures that
3188 * support it, this is what the code below does,
3191 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3193 /* Here are how the values map:
3199 * So, as above with the explicit alpha checks, the
3200 * breakpoints are at 64 and 196.
3202 if (inrow[0] & 0x80) back_i += 9; /* red */
3203 if (inrow[0] & 0x40) back_i += 9;
3204 if (inrow[0] & 0x80) back_i += 3; /* green */
3205 if (inrow[0] & 0x40) back_i += 3;
3206 if (inrow[0] & 0x80) back_i += 1; /* blue */
3207 if (inrow[0] & 0x40) back_i += 1;
3209 *outrow = (png_byte)back_i;
3227 png_image_read_colormapped(png_voidp argument)
3229 png_image_read_control *display = png_voidcast(png_image_read_control*,
3231 png_imagep image = display->image;
3232 png_controlp control = image->opaque;
3233 png_structrp png_ptr = control->png_ptr;
3234 png_inforp info_ptr = control->info_ptr;
3236 int passes = 0; /* As a flag */
3238 PNG_SKIP_CHUNKS(png_ptr);
3240 /* Update the 'info' structure and make sure the result is as required; first
3241 * make sure to turn on the interlace handling if it will be required
3242 * (because it can't be turned on *after* the call to png_read_update_info!)
3244 if (display->colormap_processing == PNG_CMAP_NONE)
3245 passes = png_set_interlace_handling(png_ptr);
3247 png_read_update_info(png_ptr, info_ptr);
3249 /* The expected output can be deduced from the colormap_processing option. */
3250 switch (display->colormap_processing)
3253 /* Output must be one channel and one byte per pixel, the output
3254 * encoding can be anything.
3256 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3257 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3258 info_ptr->bit_depth == 8)
3263 case PNG_CMAP_TRANS:
3265 /* Output must be two channels and the 'G' one must be sRGB, the latter
3266 * can be checked with an exact number because it should have been set
3267 * to this number above!
3269 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3270 info_ptr->bit_depth == 8 &&
3271 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3272 image->colormap_entries == 256)
3278 /* Output must be 8-bit sRGB encoded RGB */
3279 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3280 info_ptr->bit_depth == 8 &&
3281 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3282 image->colormap_entries == 216)
3287 case PNG_CMAP_RGB_ALPHA:
3288 /* Output must be 8-bit sRGB encoded RGBA */
3289 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3290 info_ptr->bit_depth == 8 &&
3291 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3292 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3295 /* goto bad_output; */
3300 png_error(png_ptr, "bad color-map processing (internal error)");
3303 /* Now read the rows. Do this here if it is possible to read directly into
3304 * the output buffer, otherwise allocate a local row buffer of the maximum
3305 * size libpng requires and call the relevant processing routine safely.
3308 png_voidp first_row = display->buffer;
3309 ptrdiff_t row_bytes = display->row_stride;
3311 /* The following expression is designed to work correctly whether it gives
3312 * a signed or an unsigned result.
3316 char *ptr = png_voidcast(char*, first_row);
3317 ptr += (image->height-1) * (-row_bytes);
3318 first_row = png_voidcast(png_voidp, ptr);
3321 display->first_row = first_row;
3322 display->row_bytes = row_bytes;
3328 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3330 display->local_row = row;
3331 result = png_safe_execute(image, png_image_read_and_map, display);
3332 display->local_row = NULL;
3333 png_free(png_ptr, row);
3340 png_alloc_size_t row_bytes = display->row_bytes;
3342 while (--passes >= 0)
3344 png_uint_32 y = image->height;
3345 png_bytep row = png_voidcast(png_bytep, display->first_row);
3349 png_read_row(png_ptr, row, NULL);
3358 /* Just the row reading part of png_image_read. */
3360 png_image_read_composite(png_voidp argument)
3362 png_image_read_control *display = png_voidcast(png_image_read_control*,
3364 png_imagep image = display->image;
3365 png_structrp png_ptr = image->opaque->png_ptr;
3368 switch (png_ptr->interlaced)
3370 case PNG_INTERLACE_NONE:
3374 case PNG_INTERLACE_ADAM7:
3375 passes = PNG_INTERLACE_ADAM7_PASSES;
3379 png_error(png_ptr, "unknown interlace type");
3383 png_uint_32 height = image->height;
3384 png_uint_32 width = image->width;
3385 ptrdiff_t step_row = display->row_bytes;
3386 unsigned int channels =
3387 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3390 for (pass = 0; pass < passes; ++pass)
3392 unsigned int startx, stepx, stepy;
3395 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3397 /* The row may be empty for a short image: */
3398 if (PNG_PASS_COLS(width, pass) == 0)
3401 startx = PNG_PASS_START_COL(pass) * channels;
3402 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3403 y = PNG_PASS_START_ROW(pass);
3404 stepy = PNG_PASS_ROW_OFFSET(pass);
3415 for (; y<height; y += stepy)
3417 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3419 png_const_bytep end_row;
3421 /* Read the row, which is packed: */
3422 png_read_row(png_ptr, inrow, NULL);
3424 outrow = png_voidcast(png_bytep, display->first_row);
3425 outrow += y * step_row;
3426 end_row = outrow + width * channels;
3428 /* Now do the composition on each pixel in this row. */
3430 for (; outrow < end_row; outrow += stepx)
3432 png_byte alpha = inrow[channels];
3434 if (alpha > 0) /* else no change to the output */
3438 for (c=0; c<channels; ++c)
3440 png_uint_32 component = inrow[c];
3442 if (alpha < 255) /* else just use component */
3444 /* This is PNG_OPTIMIZED_ALPHA, the component value
3445 * is a linear 8-bit value. Combine this with the
3446 * current outrow[c] value which is sRGB encoded.
3447 * Arithmetic here is 16-bits to preserve the output
3450 component *= 257*255; /* =65535 */
3451 component += (255-alpha)*png_sRGB_table[outrow[c]];
3453 /* So 'component' is scaled by 255*65535 and is
3454 * therefore appropriate for the sRGB to linear
3457 component = PNG_sRGB_FROM_LINEAR(component);
3460 outrow[c] = (png_byte)component;
3464 inrow += channels+1; /* components and alpha channel */
3473 /* The do_local_background case; called when all the following transforms are to
3480 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3481 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3482 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3483 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3484 * row and handles the removal or pre-multiplication of the alpha channel.
3487 png_image_read_background(png_voidp argument)
3489 png_image_read_control *display = png_voidcast(png_image_read_control*,
3491 png_imagep image = display->image;
3492 png_structrp png_ptr = image->opaque->png_ptr;
3493 png_inforp info_ptr = image->opaque->info_ptr;
3494 png_uint_32 height = image->height;
3495 png_uint_32 width = image->width;
3498 /* Double check the convoluted logic below. We expect to get here with
3499 * libpng doing rgb to gray and gamma correction but background processing
3500 * left to the png_image_read_background function. The rows libpng produce
3501 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3503 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3504 png_error(png_ptr, "lost rgb to gray");
3506 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3507 png_error(png_ptr, "unexpected compose");
3509 if (png_get_channels(png_ptr, info_ptr) != 2)
3510 png_error(png_ptr, "lost/gained channels");
3512 /* Expect the 8-bit case to always remove the alpha channel */
3513 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3514 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3515 png_error(png_ptr, "unexpected 8-bit transformation");
3517 switch (png_ptr->interlaced)
3519 case PNG_INTERLACE_NONE:
3523 case PNG_INTERLACE_ADAM7:
3524 passes = PNG_INTERLACE_ADAM7_PASSES;
3528 png_error(png_ptr, "unknown interlace type");
3531 /* Use direct access to info_ptr here because otherwise the simplified API
3532 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3533 * checking the value after libpng expansions, not the original value in the
3536 switch (info_ptr->bit_depth)
3539 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3540 * to be removed by composing on a background: either the row if
3541 * display->background is NULL or display->background->green if not.
3542 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3545 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3546 ptrdiff_t step_row = display->row_bytes;
3548 for (pass = 0; pass < passes; ++pass)
3550 png_bytep row = png_voidcast(png_bytep,
3551 display->first_row);
3552 unsigned int startx, stepx, stepy;
3555 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3557 /* The row may be empty for a short image: */
3558 if (PNG_PASS_COLS(width, pass) == 0)
3561 startx = PNG_PASS_START_COL(pass);
3562 stepx = PNG_PASS_COL_OFFSET(pass);
3563 y = PNG_PASS_START_ROW(pass);
3564 stepy = PNG_PASS_ROW_OFFSET(pass);
3574 if (display->background == NULL)
3576 for (; y<height; y += stepy)
3578 png_bytep inrow = png_voidcast(png_bytep,
3579 display->local_row);
3580 png_bytep outrow = first_row + y * step_row;
3581 png_const_bytep end_row = outrow + width;
3583 /* Read the row, which is packed: */
3584 png_read_row(png_ptr, inrow, NULL);
3586 /* Now do the composition on each pixel in this row. */
3588 for (; outrow < end_row; outrow += stepx)
3590 png_byte alpha = inrow[1];
3592 if (alpha > 0) /* else no change to the output */
3594 png_uint_32 component = inrow[0];
3596 if (alpha < 255) /* else just use component */
3598 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3599 * necessary to invert the sRGB transfer
3600 * function and multiply the alpha out.
3602 component = png_sRGB_table[component] * alpha;
3603 component += png_sRGB_table[outrow[0]] *
3605 component = PNG_sRGB_FROM_LINEAR(component);
3608 outrow[0] = (png_byte)component;
3611 inrow += 2; /* gray and alpha channel */
3616 else /* constant background value */
3618 png_byte background8 = display->background->green;
3619 png_uint_16 background = png_sRGB_table[background8];
3621 for (; y<height; y += stepy)
3623 png_bytep inrow = png_voidcast(png_bytep,
3624 display->local_row);
3625 png_bytep outrow = first_row + y * step_row;
3626 png_const_bytep end_row = outrow + width;
3628 /* Read the row, which is packed: */
3629 png_read_row(png_ptr, inrow, NULL);
3631 /* Now do the composition on each pixel in this row. */
3633 for (; outrow < end_row; outrow += stepx)
3635 png_byte alpha = inrow[1];
3637 if (alpha > 0) /* else use background */
3639 png_uint_32 component = inrow[0];
3641 if (alpha < 255) /* else just use component */
3643 component = png_sRGB_table[component] * alpha;
3644 component += background * (255-alpha);
3645 component = PNG_sRGB_FROM_LINEAR(component);
3648 outrow[0] = (png_byte)component;
3652 outrow[0] = background8;
3654 inrow += 2; /* gray and alpha channel */
3657 row += display->row_bytes;
3665 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3666 * still be done and, maybe, the alpha channel removed. This code also
3667 * handles the alpha-first option.
3670 png_uint_16p first_row = png_voidcast(png_uint_16p,
3671 display->first_row);
3672 /* The division by two is safe because the caller passed in a
3673 * stride which was multiplied by 2 (below) to get row_bytes.
3675 ptrdiff_t step_row = display->row_bytes / 2;
3676 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3677 unsigned int outchannels = 1+preserve_alpha;
3680 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3681 if (preserve_alpha != 0 &&
3682 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3686 for (pass = 0; pass < passes; ++pass)
3688 unsigned int startx, stepx, stepy;
3691 /* The 'x' start and step are adjusted to output components here.
3693 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3695 /* The row may be empty for a short image: */
3696 if (PNG_PASS_COLS(width, pass) == 0)
3699 startx = PNG_PASS_START_COL(pass) * outchannels;
3700 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3701 y = PNG_PASS_START_ROW(pass);
3702 stepy = PNG_PASS_ROW_OFFSET(pass);
3709 stepx = outchannels;
3713 for (; y<height; y += stepy)
3715 png_const_uint_16p inrow;
3716 png_uint_16p outrow = first_row + y*step_row;
3717 png_uint_16p end_row = outrow + width * outchannels;
3719 /* Read the row, which is packed: */
3720 png_read_row(png_ptr, png_voidcast(png_bytep,
3721 display->local_row), NULL);
3722 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3724 /* Now do the pre-multiplication on each pixel in this row.
3727 for (; outrow < end_row; outrow += stepx)
3729 png_uint_32 component = inrow[0];
3730 png_uint_16 alpha = inrow[1];
3732 if (alpha > 0) /* else 0 */
3734 if (alpha < 65535) /* else just use component */
3745 outrow[swap_alpha] = (png_uint_16)component;
3746 if (preserve_alpha != 0)
3747 outrow[1 ^ swap_alpha] = alpha;
3749 inrow += 2; /* components and alpha channel */
3758 png_error(png_ptr, "unexpected bit depth");
3765 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3767 png_image_read_direct(png_voidp argument)
3769 png_image_read_control *display = png_voidcast(png_image_read_control*,
3771 png_imagep image = display->image;
3772 png_structrp png_ptr = image->opaque->png_ptr;
3773 png_inforp info_ptr = image->opaque->info_ptr;
3775 png_uint_32 format = image->format;
3776 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3777 int do_local_compose = 0;
3778 int do_local_background = 0; /* to avoid double gamma correction bug */
3781 /* Add transforms to ensure the correct output format is produced then check
3782 * that the required implementation support is there. Always expand; always
3783 * need 8 bits minimum, no palette and expanded tRNS.
3785 png_set_expand(png_ptr);
3787 /* Now check the format to see if it was modified. */
3789 png_uint_32 base_format = png_image_format(png_ptr) &
3790 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3791 png_uint_32 change = format ^ base_format;
3792 png_fixed_point output_gamma;
3793 int mode; /* alpha mode */
3795 /* Do this first so that we have a record if rgb to gray is happening. */
3796 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3798 /* gray<->color transformation required. */
3799 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3800 png_set_gray_to_rgb(png_ptr);
3804 /* libpng can't do both rgb to gray and
3805 * background/pre-multiplication if there is also significant gamma
3806 * correction, because both operations require linear colors and
3807 * the code only supports one transform doing the gamma correction.
3808 * Handle this by doing the pre-multiplication or background
3809 * operation in this code, if necessary.
3811 * TODO: fix this by rewriting pngrtran.c (!)
3813 * For the moment (given that fixing this in pngrtran.c is an
3814 * enormous change) 'do_local_background' is used to indicate that
3815 * the problem exists.
3817 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3818 do_local_background = 1/*maybe*/;
3820 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3821 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3824 change &= ~PNG_FORMAT_FLAG_COLOR;
3827 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3830 png_fixed_point input_gamma_default;
3832 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3833 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3834 input_gamma_default = PNG_GAMMA_LINEAR;
3836 input_gamma_default = PNG_DEFAULT_sRGB;
3838 /* Call png_set_alpha_mode to set the default for the input gamma; the
3839 * output gamma is set by a second call below.
3841 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3846 /* If there *is* an alpha channel in the input it must be multiplied
3847 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3849 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3850 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3853 mode = PNG_ALPHA_PNG;
3855 output_gamma = PNG_GAMMA_LINEAR;
3860 mode = PNG_ALPHA_PNG;
3861 output_gamma = PNG_DEFAULT_sRGB;
3864 /* If 'do_local_background' is set check for the presence of gamma
3865 * correction; this is part of the work-round for the libpng bug
3868 * TODO: fix libpng and remove this.
3870 if (do_local_background != 0)
3872 png_fixed_point gtest;
3874 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3875 * gamma correction, the screen gamma hasn't been set on png_struct
3876 * yet; it's set below. png_struct::gamma, however, is set to the
3879 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3880 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3881 do_local_background = 0;
3883 else if (mode == PNG_ALPHA_STANDARD)
3885 do_local_background = 2/*required*/;
3886 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3889 /* else leave as 1 for the checks below */
3892 /* If the bit-depth changes then handle that here. */
3893 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3895 if (linear != 0 /*16-bit output*/)
3896 png_set_expand_16(png_ptr);
3898 else /* 8-bit output */
3899 png_set_scale_16(png_ptr);
3901 change &= ~PNG_FORMAT_FLAG_LINEAR;
3904 /* Now the background/alpha channel changes. */
3905 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3907 /* Removing an alpha channel requires composition for the 8-bit
3908 * formats; for the 16-bit it is already done, above, by the
3909 * pre-multiplication and the channel just needs to be stripped.
3911 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3913 /* If RGB->gray is happening the alpha channel must be left and the
3914 * operation completed locally.
3916 * TODO: fix libpng and remove this.
3918 if (do_local_background != 0)
3919 do_local_background = 2/*required*/;
3921 /* 16-bit output: just remove the channel */
3922 else if (linear != 0) /* compose on black (well, pre-multiply) */
3923 png_set_strip_alpha(png_ptr);
3925 /* 8-bit output: do an appropriate compose */
3926 else if (display->background != NULL)
3930 c.index = 0; /*unused*/
3931 c.red = display->background->red;
3932 c.green = display->background->green;
3933 c.blue = display->background->blue;
3934 c.gray = display->background->green;
3936 /* This is always an 8-bit sRGB value, using the 'green' channel
3937 * for gray is much better than calculating the luminance here;
3938 * we can get off-by-one errors in that calculation relative to
3939 * the app expectations and that will show up in transparent
3942 png_set_background_fixed(png_ptr, &c,
3943 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3944 0/*gamma: not used*/);
3947 else /* compose on row: implemented below. */
3949 do_local_compose = 1;
3950 /* This leaves the alpha channel in the output, so it has to be
3951 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3952 * one so the code only has to hack on the pixels that require
3955 mode = PNG_ALPHA_OPTIMIZED;
3959 else /* output needs an alpha channel */
3961 /* This is tricky because it happens before the swap operation has
3962 * been accomplished; however, the swap does *not* swap the added
3963 * alpha channel (weird API), so it must be added in the correct
3966 png_uint_32 filler; /* opaque filler */
3975 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3976 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3978 where = PNG_FILLER_BEFORE;
3979 change &= ~PNG_FORMAT_FLAG_AFIRST;
3984 where = PNG_FILLER_AFTER;
3986 png_set_add_alpha(png_ptr, filler, where);
3989 /* This stops the (irrelevant) call to swap_alpha below. */
3990 change &= ~PNG_FORMAT_FLAG_ALPHA;
3993 /* Now set the alpha mode correctly; this is always done, even if there is
3994 * no alpha channel in either the input or the output because it correctly
3995 * sets the output gamma.
3997 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3999 # ifdef PNG_FORMAT_BGR_SUPPORTED
4000 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
4002 /* Check only the output format; PNG is never BGR; don't do this if
4003 * the output is gray, but fix up the 'format' value in that case.
4005 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
4006 png_set_bgr(png_ptr);
4009 format &= ~PNG_FORMAT_FLAG_BGR;
4011 change &= ~PNG_FORMAT_FLAG_BGR;
4015 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4016 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
4018 /* Only relevant if there is an alpha channel - it's particularly
4019 * important to handle this correctly because do_local_compose may
4020 * be set above and then libpng will keep the alpha channel for this
4023 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
4025 /* Disable this if doing a local background,
4026 * TODO: remove this when local background is no longer required.
4028 if (do_local_background != 2)
4029 png_set_swap_alpha(png_ptr);
4033 format &= ~PNG_FORMAT_FLAG_AFIRST;
4035 change &= ~PNG_FORMAT_FLAG_AFIRST;
4039 /* If the *output* is 16-bit then we need to check for a byte-swap on this
4044 PNG_CONST png_uint_16 le = 0x0001;
4046 if ((*(png_const_bytep) & le) != 0)
4047 png_set_swap(png_ptr);
4050 /* If change is not now 0 some transformation is missing - error out. */
4052 png_error(png_ptr, "png_read_image: unsupported transformation");
4055 PNG_SKIP_CHUNKS(png_ptr);
4057 /* Update the 'info' structure and make sure the result is as required; first
4058 * make sure to turn on the interlace handling if it will be required
4059 * (because it can't be turned on *after* the call to png_read_update_info!)
4061 * TODO: remove the do_local_background fixup below.
4063 if (do_local_compose == 0 && do_local_background != 2)
4064 passes = png_set_interlace_handling(png_ptr);
4066 png_read_update_info(png_ptr, info_ptr);
4069 png_uint_32 info_format = 0;
4071 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
4072 info_format |= PNG_FORMAT_FLAG_COLOR;
4074 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
4076 /* do_local_compose removes this channel below. */
4077 if (do_local_compose == 0)
4079 /* do_local_background does the same if required. */
4080 if (do_local_background != 2 ||
4081 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
4082 info_format |= PNG_FORMAT_FLAG_ALPHA;
4086 else if (do_local_compose != 0) /* internal error */
4087 png_error(png_ptr, "png_image_read: alpha channel lost");
4089 if (info_ptr->bit_depth == 16)
4090 info_format |= PNG_FORMAT_FLAG_LINEAR;
4092 # ifdef PNG_FORMAT_BGR_SUPPORTED
4093 if ((png_ptr->transformations & PNG_BGR) != 0)
4094 info_format |= PNG_FORMAT_FLAG_BGR;
4097 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4098 if (do_local_background == 2)
4100 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4101 info_format |= PNG_FORMAT_FLAG_AFIRST;
4104 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4105 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4106 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4108 if (do_local_background == 2)
4109 png_error(png_ptr, "unexpected alpha swap transformation");
4111 info_format |= PNG_FORMAT_FLAG_AFIRST;
4115 /* This is actually an internal error. */
4116 if (info_format != format)
4117 png_error(png_ptr, "png_read_image: invalid transformations");
4120 /* Now read the rows. If do_local_compose is set then it is necessary to use
4121 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4122 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4123 * display acts as a flag.
4126 png_voidp first_row = display->buffer;
4127 ptrdiff_t row_bytes = display->row_stride;
4132 /* The following expression is designed to work correctly whether it gives
4133 * a signed or an unsigned result.
4137 char *ptr = png_voidcast(char*, first_row);
4138 ptr += (image->height-1) * (-row_bytes);
4139 first_row = png_voidcast(png_voidp, ptr);
4142 display->first_row = first_row;
4143 display->row_bytes = row_bytes;
4146 if (do_local_compose != 0)
4149 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4151 display->local_row = row;
4152 result = png_safe_execute(image, png_image_read_composite, display);
4153 display->local_row = NULL;
4154 png_free(png_ptr, row);
4159 else if (do_local_background == 2)
4162 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4164 display->local_row = row;
4165 result = png_safe_execute(image, png_image_read_background, display);
4166 display->local_row = NULL;
4167 png_free(png_ptr, row);
4174 png_alloc_size_t row_bytes = display->row_bytes;
4176 while (--passes >= 0)
4178 png_uint_32 y = image->height;
4179 png_bytep row = png_voidcast(png_bytep, display->first_row);
4183 png_read_row(png_ptr, row, NULL);
4193 png_image_finish_read(png_imagep image, png_const_colorp background,
4194 void *buffer, png_int_32 row_stride, void *colormap)
4196 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4200 if (row_stride == 0)
4201 row_stride = PNG_IMAGE_ROW_STRIDE(*image);
4204 check = -row_stride;
4209 if (image->opaque != NULL && buffer != NULL &&
4210 check >= PNG_IMAGE_ROW_STRIDE(*image))
4212 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4213 (image->colormap_entries > 0 && colormap != NULL))
4216 png_image_read_control display;
4218 memset(&display, 0, (sizeof display));
4219 display.image = image;
4220 display.buffer = buffer;
4221 display.row_stride = row_stride;
4222 display.colormap = colormap;
4223 display.background = background;
4224 display.local_row = NULL;
4226 /* Choose the correct 'end' routine; for the color-map case all the
4227 * setup has already been done.
4229 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4231 png_safe_execute(image, png_image_read_colormap, &display) &&
4232 png_safe_execute(image, png_image_read_colormapped, &display);
4236 png_safe_execute(image, png_image_read_direct, &display);
4238 png_image_free(image);
4243 return png_image_error(image,
4244 "png_image_finish_read[color-map]: no color-map");
4248 return png_image_error(image,
4249 "png_image_finish_read: invalid argument");
4252 else if (image != NULL)
4253 return png_image_error(image,
4254 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4259 #endif /* SIMPLIFIED_READ */