2 /* pngwutil.c - utilities to write a PNG file
4 * Copyright (c) 2018 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * 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
16 #ifdef PNG_WRITE_SUPPORTED
18 #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
19 /* Place a 32-bit number into a buffer in PNG byte order. We work
20 * with unsigned numbers for convenience, although one supported
21 * ancillary chunk uses signed (two's complement) numbers.
24 png_save_uint_32(png_bytep buf, png_uint_32 i)
26 buf[0] = (png_byte)((i >> 24) & 0xffU);
27 buf[1] = (png_byte)((i >> 16) & 0xffU);
28 buf[2] = (png_byte)((i >> 8) & 0xffU);
29 buf[3] = (png_byte)( i & 0xffU);
32 /* Place a 16-bit number into a buffer in PNG byte order.
33 * The parameter is declared unsigned int, not png_uint_16,
34 * just to avoid potential problems on pre-ANSI C compilers.
37 png_save_uint_16(png_bytep buf, unsigned int i)
39 buf[0] = (png_byte)((i >> 8) & 0xffU);
40 buf[1] = (png_byte)( i & 0xffU);
44 /* Simple function to write the signature. If we have already written
45 * the magic bytes of the signature, or more likely, the PNG stream is
46 * being embedded into another stream and doesn't need its own signature,
47 * we should call png_set_sig_bytes() to tell libpng how many of the
48 * bytes have already been written.
51 png_write_sig(png_structrp png_ptr)
53 png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
55 #ifdef PNG_IO_STATE_SUPPORTED
56 /* Inform the I/O callback that the signature is being written */
57 png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
60 /* Write the rest of the 8 byte signature */
61 png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
62 (size_t)(8 - png_ptr->sig_bytes));
64 if (png_ptr->sig_bytes < 3)
65 png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
68 /* Write the start of a PNG chunk. The type is the chunk type.
69 * The total_length is the sum of the lengths of all the data you will be
70 * passing in png_write_chunk_data().
73 png_write_chunk_header(png_structrp png_ptr, png_uint_32 chunk_name,
78 #if defined(PNG_DEBUG) && (PNG_DEBUG > 0)
79 PNG_CSTRING_FROM_CHUNK(buf, chunk_name);
80 png_debug2(0, "Writing %s chunk, length = %lu", buf, (unsigned long)length);
86 #ifdef PNG_IO_STATE_SUPPORTED
87 /* Inform the I/O callback that the chunk header is being written.
88 * PNG_IO_CHUNK_HDR requires a single I/O call.
90 png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
93 /* Write the length and the chunk name */
94 png_save_uint_32(buf, length);
95 png_save_uint_32(buf + 4, chunk_name);
96 png_write_data(png_ptr, buf, 8);
98 /* Put the chunk name into png_ptr->chunk_name */
99 png_ptr->chunk_name = chunk_name;
101 /* Reset the crc and run it over the chunk name */
102 png_reset_crc(png_ptr);
104 png_calculate_crc(png_ptr, buf + 4, 4);
106 #ifdef PNG_IO_STATE_SUPPORTED
107 /* Inform the I/O callback that chunk data will (possibly) be written.
108 * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
110 png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
115 png_write_chunk_start(png_structrp png_ptr, png_const_bytep chunk_string,
118 png_write_chunk_header(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), length);
121 /* Write the data of a PNG chunk started with png_write_chunk_header().
122 * Note that multiple calls to this function are allowed, and that the
123 * sum of the lengths from these calls *must* add up to the total_length
124 * given to png_write_chunk_header().
127 png_write_chunk_data(png_structrp png_ptr, png_const_bytep data, size_t length)
129 /* Write the data, and run the CRC over it */
133 if (data != NULL && length > 0)
135 png_write_data(png_ptr, data, length);
137 /* Update the CRC after writing the data,
138 * in case the user I/O routine alters it.
140 png_calculate_crc(png_ptr, data, length);
144 /* Finish a chunk started with png_write_chunk_header(). */
146 png_write_chunk_end(png_structrp png_ptr)
150 if (png_ptr == NULL) return;
152 #ifdef PNG_IO_STATE_SUPPORTED
153 /* Inform the I/O callback that the chunk CRC is being written.
154 * PNG_IO_CHUNK_CRC requires a single I/O function call.
156 png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
159 /* Write the crc in a single operation */
160 png_save_uint_32(buf, png_ptr->crc);
162 png_write_data(png_ptr, buf, 4);
165 /* Write a PNG chunk all at once. The type is an array of ASCII characters
166 * representing the chunk name. The array must be at least 4 bytes in
167 * length, and does not need to be null terminated. To be safe, pass the
168 * pre-defined chunk names here, and if you need a new one, define it
169 * where the others are defined. The length is the length of the data.
170 * All the data must be present. If that is not possible, use the
171 * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
175 png_write_complete_chunk(png_structrp png_ptr, png_uint_32 chunk_name,
176 png_const_bytep data, size_t length)
181 /* On 64-bit architectures 'length' may not fit in a png_uint_32. */
182 if (length > PNG_UINT_31_MAX)
183 png_error(png_ptr, "length exceeds PNG maximum");
185 png_write_chunk_header(png_ptr, chunk_name, (png_uint_32)length);
186 png_write_chunk_data(png_ptr, data, length);
187 png_write_chunk_end(png_ptr);
190 /* This is the API that calls the internal function above. */
192 png_write_chunk(png_structrp png_ptr, png_const_bytep chunk_string,
193 png_const_bytep data, size_t length)
195 png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
199 /* This is used below to find the size of an image to pass to png_deflate_claim,
200 * so it only needs to be accurate if the size is less than 16384 bytes (the
201 * point at which a lower LZ window size can be used.)
203 static png_alloc_size_t
204 png_image_size(png_structrp png_ptr)
206 /* Only return sizes up to the maximum of a png_uint_32; do this by limiting
207 * the width and height used to 15 bits.
209 png_uint_32 h = png_ptr->height;
211 if (png_ptr->rowbytes < 32768 && h < 32768)
213 if (png_ptr->interlaced != 0)
215 /* Interlacing makes the image larger because of the replication of
216 * both the filter byte and the padding to a byte boundary.
218 png_uint_32 w = png_ptr->width;
219 unsigned int pd = png_ptr->pixel_depth;
220 png_alloc_size_t cb_base;
223 for (cb_base=0, pass=0; pass<=6; ++pass)
225 png_uint_32 pw = PNG_PASS_COLS(w, pass);
228 cb_base += (PNG_ROWBYTES(pd, pw)+1) * PNG_PASS_ROWS(h, pass);
235 return (png_ptr->rowbytes+1) * h;
242 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
243 /* This is the code to hack the first two bytes of the deflate stream (the
244 * deflate header) to correct the windowBits value to match the actual data
245 * size. Note that the second argument is the *uncompressed* size but the
246 * first argument is the *compressed* data (and it must be deflate
250 optimize_cmf(png_bytep data, png_alloc_size_t data_size)
252 /* Optimize the CMF field in the zlib stream. The resultant zlib stream is
253 * still compliant to the stream specification.
255 if (data_size <= 16384) /* else windowBits must be 15 */
257 unsigned int z_cmf = data[0]; /* zlib compression method and flags */
259 if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
261 unsigned int z_cinfo;
262 unsigned int half_z_window_size;
264 z_cinfo = z_cmf >> 4;
265 half_z_window_size = 1U << (z_cinfo + 7);
267 if (data_size <= half_z_window_size) /* else no change */
273 half_z_window_size >>= 1;
276 while (z_cinfo > 0 && data_size <= half_z_window_size);
278 z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
280 data[0] = (png_byte)z_cmf;
281 tmp = data[1] & 0xe0;
282 tmp += 0x1f - ((z_cmf << 8) + tmp) % 0x1f;
283 data[1] = (png_byte)tmp;
288 #endif /* WRITE_OPTIMIZE_CMF */
290 /* Initialize the compressor for the appropriate type of compression. */
292 png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
293 png_alloc_size_t data_size)
295 if (png_ptr->zowner != 0)
297 #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_ERROR_TEXT_SUPPORTED)
300 PNG_STRING_FROM_CHUNK(msg, owner);
303 PNG_STRING_FROM_CHUNK(msg+6, png_ptr->zowner);
304 /* So the message that results is "<chunk> using zstream"; this is an
305 * internal error, but is very useful for debugging. i18n requirements
308 (void)png_safecat(msg, (sizeof msg), 10, " using zstream");
310 #if PNG_RELEASE_BUILD
311 png_warning(png_ptr, msg);
313 /* Attempt sane error recovery */
314 if (png_ptr->zowner == png_IDAT) /* don't steal from IDAT */
316 png_ptr->zstream.msg = PNGZ_MSG_CAST("in use by IDAT");
317 return Z_STREAM_ERROR;
322 png_error(png_ptr, msg);
327 int level = png_ptr->zlib_level;
328 int method = png_ptr->zlib_method;
329 int windowBits = png_ptr->zlib_window_bits;
330 int memLevel = png_ptr->zlib_mem_level;
331 int strategy; /* set below */
332 int ret; /* zlib return code */
334 if (owner == png_IDAT)
336 if ((png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY) != 0)
337 strategy = png_ptr->zlib_strategy;
339 else if (png_ptr->do_filter != PNG_FILTER_NONE)
340 strategy = PNG_Z_DEFAULT_STRATEGY;
343 strategy = PNG_Z_DEFAULT_NOFILTER_STRATEGY;
348 #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
349 level = png_ptr->zlib_text_level;
350 method = png_ptr->zlib_text_method;
351 windowBits = png_ptr->zlib_text_window_bits;
352 memLevel = png_ptr->zlib_text_mem_level;
353 strategy = png_ptr->zlib_text_strategy;
355 /* If customization is not supported the values all come from the
356 * IDAT values except for the strategy, which is fixed to the
357 * default. (This is the pre-1.6.0 behavior too, although it was
358 * implemented in a very different way.)
360 strategy = Z_DEFAULT_STRATEGY;
364 /* Adjust 'windowBits' down if larger than 'data_size'; to stop this
365 * happening just pass 32768 as the data_size parameter. Notice that zlib
366 * requires an extra 262 bytes in the window in addition to the data to be
367 * able to see the whole of the data, so if data_size+262 takes us to the
368 * next windowBits size we need to fix up the value later. (Because even
369 * though deflate needs the extra window, inflate does not!)
371 if (data_size <= 16384)
373 /* IMPLEMENTATION NOTE: this 'half_window_size' stuff is only here to
374 * work round a Microsoft Visual C misbehavior which, contrary to C-90,
375 * widens the result of the following shift to 64-bits if (and,
376 * apparently, only if) it is used in a test.
378 unsigned int half_window_size = 1U << (windowBits-1);
380 while (data_size + 262 <= half_window_size)
382 half_window_size >>= 1;
387 /* Check against the previous initialized values, if any. */
388 if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0 &&
389 (png_ptr->zlib_set_level != level ||
390 png_ptr->zlib_set_method != method ||
391 png_ptr->zlib_set_window_bits != windowBits ||
392 png_ptr->zlib_set_mem_level != memLevel ||
393 png_ptr->zlib_set_strategy != strategy))
395 if (deflateEnd(&png_ptr->zstream) != Z_OK)
396 png_warning(png_ptr, "deflateEnd failed (ignored)");
398 png_ptr->flags &= ~PNG_FLAG_ZSTREAM_INITIALIZED;
401 /* For safety clear out the input and output pointers (currently zlib
402 * doesn't use them on Init, but it might in the future).
404 png_ptr->zstream.next_in = NULL;
405 png_ptr->zstream.avail_in = 0;
406 png_ptr->zstream.next_out = NULL;
407 png_ptr->zstream.avail_out = 0;
409 /* Now initialize if required, setting the new parameters, otherwise just
410 * do a simple reset to the previous parameters.
412 if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
413 ret = deflateReset(&png_ptr->zstream);
417 ret = deflateInit2(&png_ptr->zstream, level, method, windowBits,
421 png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
424 /* The return code is from either deflateReset or deflateInit2; they have
425 * pretty much the same set of error codes.
428 png_ptr->zowner = owner;
431 png_zstream_error(png_ptr, ret);
437 /* Clean up (or trim) a linked list of compression buffers. */
439 png_free_buffer_list(png_structrp png_ptr, png_compression_bufferp *listp)
441 png_compression_bufferp list = *listp;
449 png_compression_bufferp next = list->next;
451 png_free(png_ptr, list);
454 while (list != NULL);
458 #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
459 /* This pair of functions encapsulates the operation of (a) compressing a
460 * text string, and (b) issuing it later as a series of chunk data writes.
461 * The compression_state structure is shared context for these functions
462 * set up by the caller to allow access to the relevant local variables.
464 * compression_buffer (new in 1.6.0) is just a linked list of zbuffer_size
465 * temporary buffers. From 1.6.0 it is retained in png_struct so that it will
466 * be correctly freed in the event of a write error (previous implementations
467 * just leaked memory.)
471 png_const_bytep input; /* The uncompressed input data */
472 png_alloc_size_t input_len; /* Its length */
473 png_uint_32 output_len; /* Final compressed length */
474 png_byte output[1024]; /* First block of output */
478 png_text_compress_init(compression_state *comp, png_const_bytep input,
479 png_alloc_size_t input_len)
482 comp->input_len = input_len;
483 comp->output_len = 0;
486 /* Compress the data in the compression state input */
488 png_text_compress(png_structrp png_ptr, png_uint_32 chunk_name,
489 compression_state *comp, png_uint_32 prefix_len)
493 /* To find the length of the output it is necessary to first compress the
494 * input. The result is buffered rather than using the two-pass algorithm
495 * that is used on the inflate side; deflate is assumed to be slower and a
496 * PNG writer is assumed to have more memory available than a PNG reader.
498 * IMPLEMENTATION NOTE: the zlib API deflateBound() can be used to find an
499 * upper limit on the output size, but it is always bigger than the input
500 * size so it is likely to be more efficient to use this linked-list
503 ret = png_deflate_claim(png_ptr, chunk_name, comp->input_len);
508 /* Set up the compression buffers, we need a loop here to avoid overflowing a
509 * uInt. Use ZLIB_IO_MAX to limit the input. The output is always limited
510 * by the output buffer size, so there is no need to check that. Since this
511 * is ANSI-C we know that an 'int', hence a uInt, is always at least 16 bits
515 png_compression_bufferp *end = &png_ptr->zbuffer_list;
516 png_alloc_size_t input_len = comp->input_len; /* may be zero! */
517 png_uint_32 output_len;
519 /* zlib updates these for us: */
520 png_ptr->zstream.next_in = PNGZ_INPUT_CAST(comp->input);
521 png_ptr->zstream.avail_in = 0; /* Set below */
522 png_ptr->zstream.next_out = comp->output;
523 png_ptr->zstream.avail_out = (sizeof comp->output);
525 output_len = png_ptr->zstream.avail_out;
529 uInt avail_in = ZLIB_IO_MAX;
531 if (avail_in > input_len)
532 avail_in = (uInt)input_len;
534 input_len -= avail_in;
536 png_ptr->zstream.avail_in = avail_in;
538 if (png_ptr->zstream.avail_out == 0)
540 png_compression_buffer *next;
542 /* Chunk data is limited to 2^31 bytes in length, so the prefix
543 * length must be counted here.
545 if (output_len + prefix_len > PNG_UINT_31_MAX)
551 /* Need a new (malloc'ed) buffer, but there may be one present
557 next = png_voidcast(png_compression_bufferp, png_malloc_base
558 (png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
566 /* Link in this buffer (so that it will be freed later) */
571 png_ptr->zstream.next_out = next->output;
572 png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
573 output_len += png_ptr->zstream.avail_out;
575 /* Move 'end' to the next buffer pointer. */
579 /* Compress the data */
580 ret = deflate(&png_ptr->zstream,
581 input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
583 /* Claw back input data that was not consumed (because avail_in is
584 * reset above every time round the loop).
586 input_len += png_ptr->zstream.avail_in;
587 png_ptr->zstream.avail_in = 0; /* safety */
591 /* There may be some space left in the last output buffer. This needs to
592 * be subtracted from output_len.
594 output_len -= png_ptr->zstream.avail_out;
595 png_ptr->zstream.avail_out = 0; /* safety */
596 comp->output_len = output_len;
598 /* Now double check the output length, put in a custom message if it is
599 * too long. Otherwise ensure the z_stream::msg pointer is set to
602 if (output_len + prefix_len >= PNG_UINT_31_MAX)
604 png_ptr->zstream.msg = PNGZ_MSG_CAST("compressed data too long");
609 png_zstream_error(png_ptr, ret);
611 /* Reset zlib for another zTXt/iTXt or image data */
614 /* The only success case is Z_STREAM_END, input_len must be 0; if not this
615 * is an internal error.
617 if (ret == Z_STREAM_END && input_len == 0)
619 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
620 /* Fix up the deflate header, if required */
621 optimize_cmf(comp->output, comp->input_len);
623 /* But Z_OK is returned, not Z_STREAM_END; this allows the claim
624 * function above to return Z_STREAM_END on an error (though it never
625 * does in the current versions of zlib.)
635 /* Ship the compressed text out via chunk writes */
637 png_write_compressed_data_out(png_structrp png_ptr, compression_state *comp)
639 png_uint_32 output_len = comp->output_len;
640 png_const_bytep output = comp->output;
641 png_uint_32 avail = (sizeof comp->output);
642 png_compression_buffer *next = png_ptr->zbuffer_list;
646 if (avail > output_len)
649 png_write_chunk_data(png_ptr, output, avail);
653 if (output_len == 0 || next == NULL)
656 avail = png_ptr->zbuffer_size;
657 output = next->output;
661 /* This is an internal error; 'next' must have been NULL! */
663 png_error(png_ptr, "error writing ancillary chunked compressed data");
665 #endif /* WRITE_COMPRESSED_TEXT */
667 /* Write the IHDR chunk, and update the png_struct with the necessary
668 * information. Note that the rest of this code depends upon this
669 * information being correct.
672 png_write_IHDR(png_structrp png_ptr, png_uint_32 width, png_uint_32 height,
673 int bit_depth, int color_type, int compression_type, int filter_type,
676 png_byte buf[13]; /* Buffer to store the IHDR info */
677 int is_invalid_depth;
679 png_debug(1, "in png_write_IHDR");
681 /* Check that we have valid input data from the application info */
684 case PNG_COLOR_TYPE_GRAY:
691 #ifdef PNG_WRITE_16BIT_SUPPORTED
694 png_ptr->channels = 1; break;
698 "Invalid bit depth for grayscale image");
702 case PNG_COLOR_TYPE_RGB:
703 is_invalid_depth = (bit_depth != 8);
704 #ifdef PNG_WRITE_16BIT_SUPPORTED
705 is_invalid_depth = (is_invalid_depth && bit_depth != 16);
707 if (is_invalid_depth)
708 png_error(png_ptr, "Invalid bit depth for RGB image");
710 png_ptr->channels = 3;
713 case PNG_COLOR_TYPE_PALETTE:
720 png_ptr->channels = 1;
724 png_error(png_ptr, "Invalid bit depth for paletted image");
728 case PNG_COLOR_TYPE_GRAY_ALPHA:
729 is_invalid_depth = (bit_depth != 8);
730 #ifdef PNG_WRITE_16BIT_SUPPORTED
731 is_invalid_depth = (is_invalid_depth && bit_depth != 16);
733 if (is_invalid_depth)
734 png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
736 png_ptr->channels = 2;
739 case PNG_COLOR_TYPE_RGB_ALPHA:
740 is_invalid_depth = (bit_depth != 8);
741 #ifdef PNG_WRITE_16BIT_SUPPORTED
742 is_invalid_depth = (is_invalid_depth && bit_depth != 16);
744 if (is_invalid_depth)
745 png_error(png_ptr, "Invalid bit depth for RGBA image");
747 png_ptr->channels = 4;
751 png_error(png_ptr, "Invalid image color type specified");
754 if (compression_type != PNG_COMPRESSION_TYPE_BASE)
756 png_warning(png_ptr, "Invalid compression type specified");
757 compression_type = PNG_COMPRESSION_TYPE_BASE;
760 /* Write filter_method 64 (intrapixel differencing) only if
761 * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
762 * 2. Libpng did not write a PNG signature (this filter_method is only
763 * used in PNG datastreams that are embedded in MNG datastreams) and
764 * 3. The application called png_permit_mng_features with a mask that
765 * included PNG_FLAG_MNG_FILTER_64 and
766 * 4. The filter_method is 64 and
767 * 5. The color_type is RGB or RGBA
770 #ifdef PNG_MNG_FEATURES_SUPPORTED
771 !((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
772 ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
773 (color_type == PNG_COLOR_TYPE_RGB ||
774 color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
775 (filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
777 filter_type != PNG_FILTER_TYPE_BASE)
779 png_warning(png_ptr, "Invalid filter type specified");
780 filter_type = PNG_FILTER_TYPE_BASE;
783 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
784 if (interlace_type != PNG_INTERLACE_NONE &&
785 interlace_type != PNG_INTERLACE_ADAM7)
787 png_warning(png_ptr, "Invalid interlace type specified");
788 interlace_type = PNG_INTERLACE_ADAM7;
791 interlace_type=PNG_INTERLACE_NONE;
794 /* Save the relevant information */
795 png_ptr->bit_depth = (png_byte)bit_depth;
796 png_ptr->color_type = (png_byte)color_type;
797 png_ptr->interlaced = (png_byte)interlace_type;
798 #ifdef PNG_MNG_FEATURES_SUPPORTED
799 png_ptr->filter_type = (png_byte)filter_type;
801 png_ptr->compression_type = (png_byte)compression_type;
802 png_ptr->width = width;
803 png_ptr->height = height;
805 png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
806 png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
807 /* Set the usr info, so any transformations can modify it */
808 png_ptr->usr_width = png_ptr->width;
809 png_ptr->usr_bit_depth = png_ptr->bit_depth;
810 png_ptr->usr_channels = png_ptr->channels;
812 /* Pack the header information into the buffer */
813 png_save_uint_32(buf, width);
814 png_save_uint_32(buf + 4, height);
815 buf[8] = (png_byte)bit_depth;
816 buf[9] = (png_byte)color_type;
817 buf[10] = (png_byte)compression_type;
818 buf[11] = (png_byte)filter_type;
819 buf[12] = (png_byte)interlace_type;
821 /* Write the chunk */
822 png_write_complete_chunk(png_ptr, png_IHDR, buf, 13);
824 #ifdef PNG_WRITE_APNG_SUPPORTED
825 png_ptr->first_frame_width = width;
826 png_ptr->first_frame_height = height;
829 if ((png_ptr->do_filter) == PNG_NO_FILTERS)
831 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
832 png_ptr->bit_depth < 8)
833 png_ptr->do_filter = PNG_FILTER_NONE;
836 png_ptr->do_filter = PNG_ALL_FILTERS;
839 png_ptr->mode = PNG_HAVE_IHDR; /* not READY_FOR_ZTXT */
842 /* Write the palette. We are careful not to trust png_color to be in the
843 * correct order for PNG, so people can redefine it to any convenient
847 png_write_PLTE(png_structrp png_ptr, png_const_colorp palette,
850 png_uint_32 max_palette_length, i;
851 png_const_colorp pal_ptr;
854 png_debug(1, "in png_write_PLTE");
856 max_palette_length = (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
857 (1 << png_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
860 #ifdef PNG_MNG_FEATURES_SUPPORTED
861 (png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) == 0 &&
863 num_pal == 0) || num_pal > max_palette_length)
865 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
867 png_error(png_ptr, "Invalid number of colors in palette");
872 png_warning(png_ptr, "Invalid number of colors in palette");
877 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
880 "Ignoring request to write a PLTE chunk in grayscale PNG");
885 png_ptr->num_palette = (png_uint_16)num_pal;
886 png_debug1(3, "num_palette = %d", png_ptr->num_palette);
888 png_write_chunk_header(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
889 #ifdef PNG_POINTER_INDEXING_SUPPORTED
891 for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
893 buf[0] = pal_ptr->red;
894 buf[1] = pal_ptr->green;
895 buf[2] = pal_ptr->blue;
896 png_write_chunk_data(png_ptr, buf, 3);
900 /* This is a little slower but some buggy compilers need to do this
905 for (i = 0; i < num_pal; i++)
907 buf[0] = pal_ptr[i].red;
908 buf[1] = pal_ptr[i].green;
909 buf[2] = pal_ptr[i].blue;
910 png_write_chunk_data(png_ptr, buf, 3);
914 png_write_chunk_end(png_ptr);
915 png_ptr->mode |= PNG_HAVE_PLTE;
918 /* This is similar to png_text_compress, above, except that it does not require
919 * all of the data at once and, instead of buffering the compressed result,
920 * writes it as IDAT chunks. Unlike png_text_compress it *can* png_error out
921 * because it calls the write interface. As a result it does its own error
922 * reporting and does not return an error code. In the event of error it will
923 * just call png_error. The input data length may exceed 32-bits. The 'flush'
924 * parameter is exactly the same as that to deflate, with the following
927 * Z_NO_FLUSH: normal incremental output of compressed data
928 * Z_SYNC_FLUSH: do a SYNC_FLUSH, used by png_write_flush
929 * Z_FINISH: this is the end of the input, do a Z_FINISH and clean up
931 * The routine manages the acquire and release of the png_ptr->zstream by
932 * checking and (at the end) clearing png_ptr->zowner; it does some sanity
933 * checks on the 'mode' flags while doing this.
936 png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
937 png_alloc_size_t input_len, int flush)
939 if (png_ptr->zowner != png_IDAT)
941 /* First time. Ensure we have a temporary buffer for compression and
942 * trim the buffer list if it has more than one entry to free memory.
943 * If 'WRITE_COMPRESSED_TEXT' is not set the list will never have been
944 * created at this point, but the check here is quick and safe.
946 if (png_ptr->zbuffer_list == NULL)
948 png_ptr->zbuffer_list = png_voidcast(png_compression_bufferp,
949 png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
950 png_ptr->zbuffer_list->next = NULL;
954 png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list->next);
956 /* It is a terminal error if we can't claim the zstream. */
957 if (png_deflate_claim(png_ptr, png_IDAT, png_image_size(png_ptr)) != Z_OK)
958 png_error(png_ptr, png_ptr->zstream.msg);
960 /* The output state is maintained in png_ptr->zstream, so it must be
961 * initialized here after the claim.
963 png_ptr->zstream.next_out = png_ptr->zbuffer_list->output;
964 png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
967 /* Now loop reading and writing until all the input is consumed or an error
968 * terminates the operation. The _out values are maintained across calls to
969 * this function, but the input must be reset each time.
971 png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
972 png_ptr->zstream.avail_in = 0; /* set below */
977 /* INPUT: from the row data */
978 uInt avail = ZLIB_IO_MAX;
980 if (avail > input_len)
981 avail = (uInt)input_len; /* safe because of the check */
983 png_ptr->zstream.avail_in = avail;
986 ret = deflate(&png_ptr->zstream, input_len > 0 ? Z_NO_FLUSH : flush);
988 /* Include as-yet unconsumed input */
989 input_len += png_ptr->zstream.avail_in;
990 png_ptr->zstream.avail_in = 0;
992 /* OUTPUT: write complete IDAT chunks when avail_out drops to zero. Note
993 * that these two zstream fields are preserved across the calls, therefore
994 * there is no need to set these up on entry to the loop.
996 if (png_ptr->zstream.avail_out == 0)
998 png_bytep data = png_ptr->zbuffer_list->output;
999 uInt size = png_ptr->zbuffer_size;
1001 /* Write an IDAT containing the data then reset the buffer. The
1002 * first IDAT may need deflate header optimization.
1004 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
1005 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0 &&
1006 png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
1007 optimize_cmf(data, png_image_size(png_ptr));
1011 #ifdef PNG_WRITE_APNG_SUPPORTED
1013 if (png_ptr->num_frames_written == 0)
1015 png_write_complete_chunk(png_ptr, png_IDAT, data, size);
1016 #ifdef PNG_WRITE_APNG_SUPPORTED
1018 png_write_fdAT(png_ptr, data, size);
1020 #endif /* PNG_WRITE_APNG_SUPPORTED */
1021 png_ptr->mode |= PNG_HAVE_IDAT;
1023 png_ptr->zstream.next_out = data;
1024 png_ptr->zstream.avail_out = size;
1026 /* For SYNC_FLUSH or FINISH it is essential to keep calling zlib with
1027 * the same flush parameter until it has finished output, for NO_FLUSH
1028 * it doesn't matter.
1030 if (ret == Z_OK && flush != Z_NO_FLUSH)
1034 /* The order of these checks doesn't matter much; it just affects which
1035 * possible error might be detected if multiple things go wrong at once.
1037 if (ret == Z_OK) /* most likely return code! */
1039 /* If all the input has been consumed then just return. If Z_FINISH
1040 * was used as the flush parameter something has gone wrong if we get
1045 if (flush == Z_FINISH)
1046 png_error(png_ptr, "Z_OK on Z_FINISH with output space");
1052 else if (ret == Z_STREAM_END && flush == Z_FINISH)
1054 /* This is the end of the IDAT data; any pending output must be
1055 * flushed. For small PNG files we may still be at the beginning.
1057 png_bytep data = png_ptr->zbuffer_list->output;
1058 uInt size = png_ptr->zbuffer_size - png_ptr->zstream.avail_out;
1060 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
1061 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0 &&
1062 png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
1063 optimize_cmf(data, png_image_size(png_ptr));
1067 #ifdef PNG_WRITE_APNG_SUPPORTED
1069 if (png_ptr->num_frames_written == 0)
1071 png_write_complete_chunk(png_ptr, png_IDAT, data, size);
1072 #ifdef PNG_WRITE_APNG_SUPPORTED
1074 png_write_fdAT(png_ptr, data, size);
1076 #endif /* PNG_WRITE_APNG_SUPPORTED */
1078 png_ptr->zstream.avail_out = 0;
1079 png_ptr->zstream.next_out = NULL;
1080 png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
1082 png_ptr->zowner = 0; /* Release the stream */
1088 /* This is an error condition. */
1089 png_zstream_error(png_ptr, ret);
1090 png_error(png_ptr, png_ptr->zstream.msg);
1095 /* Write an IEND chunk */
1097 png_write_IEND(png_structrp png_ptr)
1099 png_debug(1, "in png_write_IEND");
1101 png_write_complete_chunk(png_ptr, png_IEND, NULL, 0);
1102 png_ptr->mode |= PNG_HAVE_IEND;
1105 #ifdef PNG_WRITE_gAMA_SUPPORTED
1106 /* Write a gAMA chunk */
1108 png_write_gAMA_fixed(png_structrp png_ptr, png_fixed_point file_gamma)
1112 png_debug(1, "in png_write_gAMA");
1114 /* file_gamma is saved in 1/100,000ths */
1115 png_save_uint_32(buf, (png_uint_32)file_gamma);
1116 png_write_complete_chunk(png_ptr, png_gAMA, buf, 4);
1120 #ifdef PNG_WRITE_sRGB_SUPPORTED
1121 /* Write a sRGB chunk */
1123 png_write_sRGB(png_structrp png_ptr, int srgb_intent)
1127 png_debug(1, "in png_write_sRGB");
1129 if (srgb_intent >= PNG_sRGB_INTENT_LAST)
1130 png_warning(png_ptr,
1131 "Invalid sRGB rendering intent specified");
1133 buf[0]=(png_byte)srgb_intent;
1134 png_write_complete_chunk(png_ptr, png_sRGB, buf, 1);
1138 #ifdef PNG_WRITE_iCCP_SUPPORTED
1139 /* Write an iCCP chunk */
1141 png_write_iCCP(png_structrp png_ptr, png_const_charp name,
1142 png_const_bytep profile)
1144 png_uint_32 name_len;
1145 png_uint_32 profile_len;
1146 png_byte new_name[81]; /* 1 byte for the compression byte */
1147 compression_state comp;
1150 png_debug(1, "in png_write_iCCP");
1152 /* These are all internal problems: the profile should have been checked
1153 * before when it was stored.
1155 if (profile == NULL)
1156 png_error(png_ptr, "No profile for iCCP chunk"); /* internal error */
1158 profile_len = png_get_uint_32(profile);
1160 if (profile_len < 132)
1161 png_error(png_ptr, "ICC profile too short");
1163 temp = (png_uint_32) (*(profile+8));
1164 if (temp > 3 && (profile_len & 0x03))
1165 png_error(png_ptr, "ICC profile length invalid (not a multiple of 4)");
1168 png_uint_32 embedded_profile_len = png_get_uint_32(profile);
1170 if (profile_len != embedded_profile_len)
1171 png_error(png_ptr, "Profile length does not match profile");
1174 name_len = png_check_keyword(png_ptr, name, new_name);
1177 png_error(png_ptr, "iCCP: invalid keyword");
1179 new_name[++name_len] = PNG_COMPRESSION_TYPE_BASE;
1181 /* Make sure we include the NULL after the name and the compression type */
1184 png_text_compress_init(&comp, profile, profile_len);
1186 /* Allow for keyword terminator and compression byte */
1187 if (png_text_compress(png_ptr, png_iCCP, &comp, name_len) != Z_OK)
1188 png_error(png_ptr, png_ptr->zstream.msg);
1190 png_write_chunk_header(png_ptr, png_iCCP, name_len + comp.output_len);
1192 png_write_chunk_data(png_ptr, new_name, name_len);
1194 png_write_compressed_data_out(png_ptr, &comp);
1196 png_write_chunk_end(png_ptr);
1200 #ifdef PNG_WRITE_sPLT_SUPPORTED
1201 /* Write a sPLT chunk */
1203 png_write_sPLT(png_structrp png_ptr, png_const_sPLT_tp spalette)
1205 png_uint_32 name_len;
1206 png_byte new_name[80];
1207 png_byte entrybuf[10];
1208 size_t entry_size = (spalette->depth == 8 ? 6 : 10);
1209 size_t palette_size = entry_size * (size_t)spalette->nentries;
1211 #ifndef PNG_POINTER_INDEXING_SUPPORTED
1215 png_debug(1, "in png_write_sPLT");
1217 name_len = png_check_keyword(png_ptr, spalette->name, new_name);
1220 png_error(png_ptr, "sPLT: invalid keyword");
1222 /* Make sure we include the NULL after the name */
1223 png_write_chunk_header(png_ptr, png_sPLT,
1224 (png_uint_32)(name_len + 2 + palette_size));
1226 png_write_chunk_data(png_ptr, (png_bytep)new_name, (size_t)(name_len + 1));
1228 png_write_chunk_data(png_ptr, &spalette->depth, 1);
1230 /* Loop through each palette entry, writing appropriately */
1231 #ifdef PNG_POINTER_INDEXING_SUPPORTED
1232 for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
1234 if (spalette->depth == 8)
1236 entrybuf[0] = (png_byte)ep->red;
1237 entrybuf[1] = (png_byte)ep->green;
1238 entrybuf[2] = (png_byte)ep->blue;
1239 entrybuf[3] = (png_byte)ep->alpha;
1240 png_save_uint_16(entrybuf + 4, ep->frequency);
1245 png_save_uint_16(entrybuf + 0, ep->red);
1246 png_save_uint_16(entrybuf + 2, ep->green);
1247 png_save_uint_16(entrybuf + 4, ep->blue);
1248 png_save_uint_16(entrybuf + 6, ep->alpha);
1249 png_save_uint_16(entrybuf + 8, ep->frequency);
1252 png_write_chunk_data(png_ptr, entrybuf, entry_size);
1255 ep=spalette->entries;
1256 for (i = 0; i>spalette->nentries; i++)
1258 if (spalette->depth == 8)
1260 entrybuf[0] = (png_byte)ep[i].red;
1261 entrybuf[1] = (png_byte)ep[i].green;
1262 entrybuf[2] = (png_byte)ep[i].blue;
1263 entrybuf[3] = (png_byte)ep[i].alpha;
1264 png_save_uint_16(entrybuf + 4, ep[i].frequency);
1269 png_save_uint_16(entrybuf + 0, ep[i].red);
1270 png_save_uint_16(entrybuf + 2, ep[i].green);
1271 png_save_uint_16(entrybuf + 4, ep[i].blue);
1272 png_save_uint_16(entrybuf + 6, ep[i].alpha);
1273 png_save_uint_16(entrybuf + 8, ep[i].frequency);
1276 png_write_chunk_data(png_ptr, entrybuf, entry_size);
1280 png_write_chunk_end(png_ptr);
1284 #ifdef PNG_WRITE_sBIT_SUPPORTED
1285 /* Write the sBIT chunk */
1287 png_write_sBIT(png_structrp png_ptr, png_const_color_8p sbit, int color_type)
1292 png_debug(1, "in png_write_sBIT");
1294 /* Make sure we don't depend upon the order of PNG_COLOR_8 */
1295 if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
1299 maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
1300 png_ptr->usr_bit_depth);
1302 if (sbit->red == 0 || sbit->red > maxbits ||
1303 sbit->green == 0 || sbit->green > maxbits ||
1304 sbit->blue == 0 || sbit->blue > maxbits)
1306 png_warning(png_ptr, "Invalid sBIT depth specified");
1311 buf[1] = sbit->green;
1312 buf[2] = sbit->blue;
1318 if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
1320 png_warning(png_ptr, "Invalid sBIT depth specified");
1324 buf[0] = sbit->gray;
1328 if ((color_type & PNG_COLOR_MASK_ALPHA) != 0)
1330 if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
1332 png_warning(png_ptr, "Invalid sBIT depth specified");
1336 buf[size++] = sbit->alpha;
1339 png_write_complete_chunk(png_ptr, png_sBIT, buf, size);
1343 #ifdef PNG_WRITE_cHRM_SUPPORTED
1344 /* Write the cHRM chunk */
1346 png_write_cHRM_fixed(png_structrp png_ptr, const png_xy *xy)
1350 png_debug(1, "in png_write_cHRM");
1352 /* Each value is saved in 1/100,000ths */
1353 png_save_int_32(buf, xy->whitex);
1354 png_save_int_32(buf + 4, xy->whitey);
1356 png_save_int_32(buf + 8, xy->redx);
1357 png_save_int_32(buf + 12, xy->redy);
1359 png_save_int_32(buf + 16, xy->greenx);
1360 png_save_int_32(buf + 20, xy->greeny);
1362 png_save_int_32(buf + 24, xy->bluex);
1363 png_save_int_32(buf + 28, xy->bluey);
1365 png_write_complete_chunk(png_ptr, png_cHRM, buf, 32);
1369 #ifdef PNG_WRITE_tRNS_SUPPORTED
1370 /* Write the tRNS chunk */
1372 png_write_tRNS(png_structrp png_ptr, png_const_bytep trans_alpha,
1373 png_const_color_16p tran, int num_trans, int color_type)
1377 png_debug(1, "in png_write_tRNS");
1379 if (color_type == PNG_COLOR_TYPE_PALETTE)
1381 if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
1383 png_app_warning(png_ptr,
1384 "Invalid number of transparent colors specified");
1388 /* Write the chunk out as it is */
1389 png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha,
1393 else if (color_type == PNG_COLOR_TYPE_GRAY)
1395 /* One 16-bit value */
1396 if (tran->gray >= (1 << png_ptr->bit_depth))
1398 png_app_warning(png_ptr,
1399 "Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
1404 png_save_uint_16(buf, tran->gray);
1405 png_write_complete_chunk(png_ptr, png_tRNS, buf, 2);
1408 else if (color_type == PNG_COLOR_TYPE_RGB)
1410 /* Three 16-bit values */
1411 png_save_uint_16(buf, tran->red);
1412 png_save_uint_16(buf + 2, tran->green);
1413 png_save_uint_16(buf + 4, tran->blue);
1414 #ifdef PNG_WRITE_16BIT_SUPPORTED
1415 if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]) != 0)
1417 if ((buf[0] | buf[2] | buf[4]) != 0)
1420 png_app_warning(png_ptr,
1421 "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
1425 png_write_complete_chunk(png_ptr, png_tRNS, buf, 6);
1430 png_app_warning(png_ptr, "Can't write tRNS with an alpha channel");
1435 #ifdef PNG_WRITE_bKGD_SUPPORTED
1436 /* Write the background chunk */
1438 png_write_bKGD(png_structrp png_ptr, png_const_color_16p back, int color_type)
1442 png_debug(1, "in png_write_bKGD");
1444 if (color_type == PNG_COLOR_TYPE_PALETTE)
1447 #ifdef PNG_MNG_FEATURES_SUPPORTED
1448 (png_ptr->num_palette != 0 ||
1449 (png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) == 0) &&
1451 back->index >= png_ptr->num_palette)
1453 png_warning(png_ptr, "Invalid background palette index");
1457 buf[0] = back->index;
1458 png_write_complete_chunk(png_ptr, png_bKGD, buf, 1);
1461 else if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
1463 png_save_uint_16(buf, back->red);
1464 png_save_uint_16(buf + 2, back->green);
1465 png_save_uint_16(buf + 4, back->blue);
1466 #ifdef PNG_WRITE_16BIT_SUPPORTED
1467 if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]) != 0)
1469 if ((buf[0] | buf[2] | buf[4]) != 0)
1472 png_warning(png_ptr,
1473 "Ignoring attempt to write 16-bit bKGD chunk "
1474 "when bit_depth is 8");
1479 png_write_complete_chunk(png_ptr, png_bKGD, buf, 6);
1484 if (back->gray >= (1 << png_ptr->bit_depth))
1486 png_warning(png_ptr,
1487 "Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
1492 png_save_uint_16(buf, back->gray);
1493 png_write_complete_chunk(png_ptr, png_bKGD, buf, 2);
1498 #ifdef PNG_WRITE_eXIf_SUPPORTED
1499 /* Write the Exif data */
1501 png_write_eXIf(png_structrp png_ptr, png_bytep exif, int num_exif)
1506 png_debug(1, "in png_write_eXIf");
1508 png_write_chunk_header(png_ptr, png_eXIf, (png_uint_32)(num_exif));
1510 for (i = 0; i < num_exif; i++)
1513 png_write_chunk_data(png_ptr, buf, 1);
1516 png_write_chunk_end(png_ptr);
1520 #ifdef PNG_WRITE_hIST_SUPPORTED
1521 /* Write the histogram */
1523 png_write_hIST(png_structrp png_ptr, png_const_uint_16p hist, int num_hist)
1528 png_debug(1, "in png_write_hIST");
1530 if (num_hist > (int)png_ptr->num_palette)
1532 png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
1533 png_ptr->num_palette);
1535 png_warning(png_ptr, "Invalid number of histogram entries specified");
1539 png_write_chunk_header(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
1541 for (i = 0; i < num_hist; i++)
1543 png_save_uint_16(buf, hist[i]);
1544 png_write_chunk_data(png_ptr, buf, 2);
1547 png_write_chunk_end(png_ptr);
1551 #ifdef PNG_WRITE_tEXt_SUPPORTED
1552 /* Write a tEXt chunk */
1554 png_write_tEXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
1557 png_uint_32 key_len;
1558 png_byte new_key[80];
1560 png_debug(1, "in png_write_tEXt");
1562 key_len = png_check_keyword(png_ptr, key, new_key);
1565 png_error(png_ptr, "tEXt: invalid keyword");
1567 if (text == NULL || *text == '\0')
1571 text_len = strlen(text);
1573 if (text_len > PNG_UINT_31_MAX - (key_len+1))
1574 png_error(png_ptr, "tEXt: text too long");
1576 /* Make sure we include the 0 after the key */
1577 png_write_chunk_header(png_ptr, png_tEXt,
1578 (png_uint_32)/*checked above*/(key_len + text_len + 1));
1580 * We leave it to the application to meet PNG-1.0 requirements on the
1581 * contents of the text. PNG-1.0 through PNG-1.2 discourage the use of
1582 * any non-Latin-1 characters except for NEWLINE. ISO PNG will forbid them.
1583 * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1585 png_write_chunk_data(png_ptr, new_key, key_len + 1);
1588 png_write_chunk_data(png_ptr, (png_const_bytep)text, text_len);
1590 png_write_chunk_end(png_ptr);
1594 #ifdef PNG_WRITE_zTXt_SUPPORTED
1595 /* Write a compressed text chunk */
1597 png_write_zTXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
1600 png_uint_32 key_len;
1601 png_byte new_key[81];
1602 compression_state comp;
1604 png_debug(1, "in png_write_zTXt");
1606 if (compression == PNG_TEXT_COMPRESSION_NONE)
1608 png_write_tEXt(png_ptr, key, text, 0);
1612 if (compression != PNG_TEXT_COMPRESSION_zTXt)
1613 png_error(png_ptr, "zTXt: invalid compression type");
1615 key_len = png_check_keyword(png_ptr, key, new_key);
1618 png_error(png_ptr, "zTXt: invalid keyword");
1620 /* Add the compression method and 1 for the keyword separator. */
1621 new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
1624 /* Compute the compressed data; do it now for the length */
1625 png_text_compress_init(&comp, (png_const_bytep)text,
1626 text == NULL ? 0 : strlen(text));
1628 if (png_text_compress(png_ptr, png_zTXt, &comp, key_len) != Z_OK)
1629 png_error(png_ptr, png_ptr->zstream.msg);
1631 /* Write start of chunk */
1632 png_write_chunk_header(png_ptr, png_zTXt, key_len + comp.output_len);
1635 png_write_chunk_data(png_ptr, new_key, key_len);
1637 /* Write the compressed data */
1638 png_write_compressed_data_out(png_ptr, &comp);
1640 /* Close the chunk */
1641 png_write_chunk_end(png_ptr);
1645 #ifdef PNG_WRITE_iTXt_SUPPORTED
1646 /* Write an iTXt chunk */
1648 png_write_iTXt(png_structrp png_ptr, int compression, png_const_charp key,
1649 png_const_charp lang, png_const_charp lang_key, png_const_charp text)
1651 png_uint_32 key_len, prefix_len;
1652 size_t lang_len, lang_key_len;
1653 png_byte new_key[82];
1654 compression_state comp;
1656 png_debug(1, "in png_write_iTXt");
1658 key_len = png_check_keyword(png_ptr, key, new_key);
1661 png_error(png_ptr, "iTXt: invalid keyword");
1663 /* Set the compression flag */
1664 switch (compression)
1666 case PNG_ITXT_COMPRESSION_NONE:
1667 case PNG_TEXT_COMPRESSION_NONE:
1668 compression = new_key[++key_len] = 0; /* no compression */
1671 case PNG_TEXT_COMPRESSION_zTXt:
1672 case PNG_ITXT_COMPRESSION_zTXt:
1673 compression = new_key[++key_len] = 1; /* compressed */
1677 png_error(png_ptr, "iTXt: invalid compression");
1680 new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
1681 ++key_len; /* for the keywod separator */
1683 /* We leave it to the application to meet PNG-1.0 requirements on the
1684 * contents of the text. PNG-1.0 through PNG-1.2 discourage the use of
1685 * any non-Latin-1 characters except for NEWLINE. ISO PNG, however,
1686 * specifies that the text is UTF-8 and this really doesn't require any
1689 * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1691 * TODO: validate the language tag correctly (see the spec.)
1693 if (lang == NULL) lang = ""; /* empty language is valid */
1694 lang_len = strlen(lang)+1;
1695 if (lang_key == NULL) lang_key = ""; /* may be empty */
1696 lang_key_len = strlen(lang_key)+1;
1697 if (text == NULL) text = ""; /* may be empty */
1699 prefix_len = key_len;
1700 if (lang_len > PNG_UINT_31_MAX-prefix_len)
1701 prefix_len = PNG_UINT_31_MAX;
1703 prefix_len = (png_uint_32)(prefix_len + lang_len);
1705 if (lang_key_len > PNG_UINT_31_MAX-prefix_len)
1706 prefix_len = PNG_UINT_31_MAX;
1708 prefix_len = (png_uint_32)(prefix_len + lang_key_len);
1710 png_text_compress_init(&comp, (png_const_bytep)text, strlen(text));
1712 if (compression != 0)
1714 if (png_text_compress(png_ptr, png_iTXt, &comp, prefix_len) != Z_OK)
1715 png_error(png_ptr, png_ptr->zstream.msg);
1720 if (comp.input_len > PNG_UINT_31_MAX-prefix_len)
1721 png_error(png_ptr, "iTXt: uncompressed text too long");
1723 /* So the string will fit in a chunk: */
1724 comp.output_len = (png_uint_32)/*SAFE*/comp.input_len;
1727 png_write_chunk_header(png_ptr, png_iTXt, comp.output_len + prefix_len);
1729 png_write_chunk_data(png_ptr, new_key, key_len);
1731 png_write_chunk_data(png_ptr, (png_const_bytep)lang, lang_len);
1733 png_write_chunk_data(png_ptr, (png_const_bytep)lang_key, lang_key_len);
1735 if (compression != 0)
1736 png_write_compressed_data_out(png_ptr, &comp);
1739 png_write_chunk_data(png_ptr, (png_const_bytep)text, comp.output_len);
1741 png_write_chunk_end(png_ptr);
1745 #ifdef PNG_WRITE_oFFs_SUPPORTED
1746 /* Write the oFFs chunk */
1748 png_write_oFFs(png_structrp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
1753 png_debug(1, "in png_write_oFFs");
1755 if (unit_type >= PNG_OFFSET_LAST)
1756 png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
1758 png_save_int_32(buf, x_offset);
1759 png_save_int_32(buf + 4, y_offset);
1760 buf[8] = (png_byte)unit_type;
1762 png_write_complete_chunk(png_ptr, png_oFFs, buf, 9);
1765 #ifdef PNG_WRITE_pCAL_SUPPORTED
1766 /* Write the pCAL chunk (described in the PNG extensions document) */
1768 png_write_pCAL(png_structrp png_ptr, png_charp purpose, png_int_32 X0,
1769 png_int_32 X1, int type, int nparams, png_const_charp units,
1772 png_uint_32 purpose_len;
1773 size_t units_len, total_len;
1774 png_size_tp params_len;
1776 png_byte new_purpose[80];
1779 png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
1781 if (type >= PNG_EQUATION_LAST)
1782 png_error(png_ptr, "Unrecognized equation type for pCAL chunk");
1784 purpose_len = png_check_keyword(png_ptr, purpose, new_purpose);
1786 if (purpose_len == 0)
1787 png_error(png_ptr, "pCAL: invalid keyword");
1789 ++purpose_len; /* terminator */
1791 png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
1792 units_len = strlen(units) + (nparams == 0 ? 0 : 1);
1793 png_debug1(3, "pCAL units length = %d", (int)units_len);
1794 total_len = purpose_len + units_len + 10;
1796 params_len = (png_size_tp)png_malloc(png_ptr,
1797 (png_alloc_size_t)((png_alloc_size_t)nparams * (sizeof (size_t))));
1799 /* Find the length of each parameter, making sure we don't count the
1800 * null terminator for the last parameter.
1802 for (i = 0; i < nparams; i++)
1804 params_len[i] = strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
1805 png_debug2(3, "pCAL parameter %d length = %lu", i,
1806 (unsigned long)params_len[i]);
1807 total_len += params_len[i];
1810 png_debug1(3, "pCAL total length = %d", (int)total_len);
1811 png_write_chunk_header(png_ptr, png_pCAL, (png_uint_32)total_len);
1812 png_write_chunk_data(png_ptr, new_purpose, purpose_len);
1813 png_save_int_32(buf, X0);
1814 png_save_int_32(buf + 4, X1);
1815 buf[8] = (png_byte)type;
1816 buf[9] = (png_byte)nparams;
1817 png_write_chunk_data(png_ptr, buf, 10);
1818 png_write_chunk_data(png_ptr, (png_const_bytep)units, (size_t)units_len);
1820 for (i = 0; i < nparams; i++)
1822 png_write_chunk_data(png_ptr, (png_const_bytep)params[i], params_len[i]);
1825 png_free(png_ptr, params_len);
1826 png_write_chunk_end(png_ptr);
1830 #ifdef PNG_WRITE_sCAL_SUPPORTED
1831 /* Write the sCAL chunk */
1833 png_write_sCAL_s(png_structrp png_ptr, int unit, png_const_charp width,
1834 png_const_charp height)
1837 size_t wlen, hlen, total_len;
1839 png_debug(1, "in png_write_sCAL_s");
1841 wlen = strlen(width);
1842 hlen = strlen(height);
1843 total_len = wlen + hlen + 2;
1847 png_warning(png_ptr, "Can't write sCAL (buffer too small)");
1851 buf[0] = (png_byte)unit;
1852 memcpy(buf + 1, width, wlen + 1); /* Append the '\0' here */
1853 memcpy(buf + wlen + 2, height, hlen); /* Do NOT append the '\0' here */
1855 png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
1856 png_write_complete_chunk(png_ptr, png_sCAL, buf, total_len);
1860 #ifdef PNG_WRITE_pHYs_SUPPORTED
1861 /* Write the pHYs chunk */
1863 png_write_pHYs(png_structrp png_ptr, png_uint_32 x_pixels_per_unit,
1864 png_uint_32 y_pixels_per_unit,
1869 png_debug(1, "in png_write_pHYs");
1871 if (unit_type >= PNG_RESOLUTION_LAST)
1872 png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
1874 png_save_uint_32(buf, x_pixels_per_unit);
1875 png_save_uint_32(buf + 4, y_pixels_per_unit);
1876 buf[8] = (png_byte)unit_type;
1878 png_write_complete_chunk(png_ptr, png_pHYs, buf, 9);
1882 #ifdef PNG_WRITE_tIME_SUPPORTED
1883 /* Write the tIME chunk. Use either png_convert_from_struct_tm()
1884 * or png_convert_from_time_t(), or fill in the structure yourself.
1887 png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
1891 png_debug(1, "in png_write_tIME");
1893 if (mod_time->month > 12 || mod_time->month < 1 ||
1894 mod_time->day > 31 || mod_time->day < 1 ||
1895 mod_time->hour > 23 || mod_time->second > 60)
1897 png_warning(png_ptr, "Invalid time specified for tIME chunk");
1901 png_save_uint_16(buf, mod_time->year);
1902 buf[2] = mod_time->month;
1903 buf[3] = mod_time->day;
1904 buf[4] = mod_time->hour;
1905 buf[5] = mod_time->minute;
1906 buf[6] = mod_time->second;
1908 png_write_complete_chunk(png_ptr, png_tIME, buf, 7);
1912 #ifdef PNG_WRITE_APNG_SUPPORTED
1914 png_write_acTL(png_structp png_ptr,
1915 png_uint_32 num_frames, png_uint_32 num_plays)
1919 png_debug(1, "in png_write_acTL");
1921 png_ptr->num_frames_to_write = num_frames;
1923 if (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN)
1926 png_save_uint_32(buf, num_frames);
1927 png_save_uint_32(buf + 4, num_plays);
1929 png_write_complete_chunk(png_ptr, png_acTL, buf, (png_size_t)8);
1933 png_write_fcTL(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
1934 png_uint_32 x_offset, png_uint_32 y_offset,
1935 png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
1940 png_debug(1, "in png_write_fcTL");
1942 if (png_ptr->num_frames_written == 0 && (x_offset != 0 || y_offset != 0))
1943 png_error(png_ptr, "x and/or y offset for the first frame aren't 0");
1944 if (png_ptr->num_frames_written == 0 &&
1945 (width != png_ptr->first_frame_width ||
1946 height != png_ptr->first_frame_height))
1947 png_error(png_ptr, "width and/or height in the first frame's fcTL "
1948 "don't match the ones in IHDR");
1950 /* more error checking */
1951 png_ensure_fcTL_is_valid(png_ptr, width, height, x_offset, y_offset,
1952 delay_num, delay_den, dispose_op, blend_op);
1954 png_save_uint_32(buf, png_ptr->next_seq_num);
1955 png_save_uint_32(buf + 4, width);
1956 png_save_uint_32(buf + 8, height);
1957 png_save_uint_32(buf + 12, x_offset);
1958 png_save_uint_32(buf + 16, y_offset);
1959 png_save_uint_16(buf + 20, delay_num);
1960 png_save_uint_16(buf + 22, delay_den);
1961 buf[24] = dispose_op;
1964 png_write_complete_chunk(png_ptr, png_fcTL, buf, (png_size_t)26);
1966 png_ptr->next_seq_num++;
1970 png_write_fdAT(png_structp png_ptr,
1971 png_const_bytep data, png_size_t length)
1975 png_write_chunk_header(png_ptr, png_fdAT, (png_uint_32)(4 + length));
1977 png_save_uint_32(buf, png_ptr->next_seq_num);
1978 png_write_chunk_data(png_ptr, buf, 4);
1980 png_write_chunk_data(png_ptr, data, length);
1982 png_write_chunk_end(png_ptr);
1984 png_ptr->next_seq_num++;
1986 #endif /* PNG_WRITE_APNG_SUPPORTED */
1988 /* Initializes the row writing capability of libpng */
1990 png_write_start_row(png_structrp png_ptr)
1992 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
1993 /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1995 /* Start of interlace block */
1996 static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1998 /* Offset to next interlace block */
1999 static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
2001 /* Start of interlace block in the y direction */
2002 static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
2004 /* Offset to next interlace block in the y direction */
2005 static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
2008 png_alloc_size_t buf_size;
2009 int usr_pixel_depth;
2011 #ifdef PNG_WRITE_FILTER_SUPPORTED
2015 png_debug(1, "in png_write_start_row");
2017 usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
2018 buf_size = PNG_ROWBYTES(usr_pixel_depth, png_ptr->width) + 1;
2020 /* 1.5.6: added to allow checking in the row write code. */
2021 png_ptr->transformed_pixel_depth = png_ptr->pixel_depth;
2022 png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;
2024 /* Set up row buffer */
2025 png_ptr->row_buf = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
2027 png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
2029 #ifdef PNG_WRITE_FILTER_SUPPORTED
2030 filters = png_ptr->do_filter;
2032 if (png_ptr->height == 1)
2033 filters &= 0xff & ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
2035 if (png_ptr->width == 1)
2036 filters &= 0xff & ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);
2039 filters = PNG_FILTER_NONE;
2041 png_ptr->do_filter = filters;
2043 if (((filters & (PNG_FILTER_SUB | PNG_FILTER_UP | PNG_FILTER_AVG |
2044 PNG_FILTER_PAETH)) != 0) && png_ptr->try_row == NULL)
2046 int num_filters = 0;
2048 png_ptr->try_row = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
2050 if (filters & PNG_FILTER_SUB)
2053 if (filters & PNG_FILTER_UP)
2056 if (filters & PNG_FILTER_AVG)
2059 if (filters & PNG_FILTER_PAETH)
2062 if (num_filters > 1)
2063 png_ptr->tst_row = png_voidcast(png_bytep, png_malloc(png_ptr,
2067 /* We only need to keep the previous row if we are using one of the following
2070 if ((filters & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH)) != 0)
2071 png_ptr->prev_row = png_voidcast(png_bytep,
2072 png_calloc(png_ptr, buf_size));
2073 #endif /* WRITE_FILTER */
2075 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
2076 /* If interlaced, we need to set up width and height of pass */
2077 if (png_ptr->interlaced != 0)
2079 if ((png_ptr->transformations & PNG_INTERLACE) == 0)
2081 png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
2082 png_pass_ystart[0]) / png_pass_yinc[0];
2084 png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
2085 png_pass_start[0]) / png_pass_inc[0];
2090 png_ptr->num_rows = png_ptr->height;
2091 png_ptr->usr_width = png_ptr->width;
2098 png_ptr->num_rows = png_ptr->height;
2099 png_ptr->usr_width = png_ptr->width;
2103 /* Internal use only. Called when finished processing a row of data. */
2105 png_write_finish_row(png_structrp png_ptr)
2107 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
2108 /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
2110 /* Start of interlace block */
2111 static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
2113 /* Offset to next interlace block */
2114 static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
2116 /* Start of interlace block in the y direction */
2117 static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
2119 /* Offset to next interlace block in the y direction */
2120 static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
2123 png_debug(1, "in png_write_finish_row");
2126 png_ptr->row_number++;
2128 /* See if we are done */
2129 if (png_ptr->row_number < png_ptr->num_rows)
2132 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
2133 /* If interlaced, go to next pass */
2134 if (png_ptr->interlaced != 0)
2136 png_ptr->row_number = 0;
2137 if ((png_ptr->transformations & PNG_INTERLACE) != 0)
2144 /* Loop until we find a non-zero width or height pass */
2149 if (png_ptr->pass >= 7)
2152 png_ptr->usr_width = (png_ptr->width +
2153 png_pass_inc[png_ptr->pass] - 1 -
2154 png_pass_start[png_ptr->pass]) /
2155 png_pass_inc[png_ptr->pass];
2157 png_ptr->num_rows = (png_ptr->height +
2158 png_pass_yinc[png_ptr->pass] - 1 -
2159 png_pass_ystart[png_ptr->pass]) /
2160 png_pass_yinc[png_ptr->pass];
2162 if ((png_ptr->transformations & PNG_INTERLACE) != 0)
2165 } while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
2169 /* Reset the row above the image for the next pass */
2170 if (png_ptr->pass < 7)
2172 if (png_ptr->prev_row != NULL)
2173 memset(png_ptr->prev_row, 0,
2174 PNG_ROWBYTES(png_ptr->usr_channels *
2175 png_ptr->usr_bit_depth, png_ptr->width) + 1);
2182 /* If we get here, we've just written the last row, so we need
2183 to flush the compressor */
2184 png_compress_IDAT(png_ptr, NULL, 0, Z_FINISH);
2187 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
2188 /* Pick out the correct pixels for the interlace pass.
2189 * The basic idea here is to go through the row with a source
2190 * pointer and a destination pointer (sp and dp), and copy the
2191 * correct pixels for the pass. As the row gets compacted,
2192 * sp will always be >= dp, so we should never overwrite anything.
2193 * See the default: case for the easiest code to understand.
2196 png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
2198 /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
2200 /* Start of interlace block */
2201 static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
2203 /* Offset to next interlace block */
2204 static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
2206 png_debug(1, "in png_do_write_interlace");
2208 /* We don't have to do anything on the last pass (6) */
2211 /* Each pixel depth is handled separately */
2212 switch (row_info->pixel_depth)
2222 png_uint_32 row_width = row_info->width;
2228 for (i = png_pass_start[pass]; i < row_width;
2229 i += png_pass_inc[pass])
2231 sp = row + (size_t)(i >> 3);
2232 value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
2233 d |= (value << shift);
2238 *dp++ = (png_byte)d;
2260 png_uint_32 row_width = row_info->width;
2266 for (i = png_pass_start[pass]; i < row_width;
2267 i += png_pass_inc[pass])
2269 sp = row + (size_t)(i >> 2);
2270 value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
2271 d |= (value << shift);
2276 *dp++ = (png_byte)d;
2297 png_uint_32 row_width = row_info->width;
2302 for (i = png_pass_start[pass]; i < row_width;
2303 i += png_pass_inc[pass])
2305 sp = row + (size_t)(i >> 1);
2306 value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
2307 d |= (value << shift);
2312 *dp++ = (png_byte)d;
2330 png_uint_32 row_width = row_info->width;
2333 /* Start at the beginning */
2336 /* Find out how many bytes each pixel takes up */
2337 pixel_bytes = (row_info->pixel_depth >> 3);
2339 /* Loop through the row, only looking at the pixels that matter */
2340 for (i = png_pass_start[pass]; i < row_width;
2341 i += png_pass_inc[pass])
2343 /* Find out where the original pixel is */
2344 sp = row + (size_t)i * pixel_bytes;
2346 /* Move the pixel */
2348 memcpy(dp, sp, pixel_bytes);
2356 /* Set new row width */
2357 row_info->width = (row_info->width +
2358 png_pass_inc[pass] - 1 -
2359 png_pass_start[pass]) /
2362 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
2369 /* This filters the row, chooses which filter to use, if it has not already
2370 * been specified by the application, and then writes the row out with the
2373 static void /* PRIVATE */
2374 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
2377 #ifdef PNG_WRITE_FILTER_SUPPORTED
2378 static size_t /* PRIVATE */
2379 png_setup_sub_row(png_structrp png_ptr, png_uint_32 bpp,
2380 size_t row_bytes, size_t lmins)
2382 png_bytep rp, dp, lp;
2387 png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
2389 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
2394 sum += 128 - abs((int)v - 128);
2396 sum += (v < 128) ? v : 256 - v;
2400 for (lp = png_ptr->row_buf + 1; i < row_bytes;
2401 i++, rp++, lp++, dp++)
2403 v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
2405 sum += 128 - abs((int)v - 128);
2407 sum += (v < 128) ? v : 256 - v;
2410 if (sum > lmins) /* We are already worse, don't continue. */
2417 static void /* PRIVATE */
2418 png_setup_sub_row_only(png_structrp png_ptr, png_uint_32 bpp,
2421 png_bytep rp, dp, lp;
2424 png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
2426 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
2432 for (lp = png_ptr->row_buf + 1; i < row_bytes;
2433 i++, rp++, lp++, dp++)
2435 *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
2439 static size_t /* PRIVATE */
2440 png_setup_up_row(png_structrp png_ptr, size_t row_bytes, size_t lmins)
2442 png_bytep rp, dp, pp;
2447 png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
2449 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2450 pp = png_ptr->prev_row + 1; i < row_bytes;
2451 i++, rp++, pp++, dp++)
2453 v = *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
2455 sum += 128 - abs((int)v - 128);
2457 sum += (v < 128) ? v : 256 - v;
2460 if (sum > lmins) /* We are already worse, don't continue. */
2466 static void /* PRIVATE */
2467 png_setup_up_row_only(png_structrp png_ptr, size_t row_bytes)
2469 png_bytep rp, dp, pp;
2472 png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
2474 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2475 pp = png_ptr->prev_row + 1; i < row_bytes;
2476 i++, rp++, pp++, dp++)
2478 *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
2482 static size_t /* PRIVATE */
2483 png_setup_avg_row(png_structrp png_ptr, png_uint_32 bpp,
2484 size_t row_bytes, size_t lmins)
2486 png_bytep rp, dp, pp, lp;
2491 png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
2493 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2494 pp = png_ptr->prev_row + 1; i < bpp; i++)
2496 v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
2499 sum += 128 - abs((int)v - 128);
2501 sum += (v < 128) ? v : 256 - v;
2505 for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
2507 v = *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
2511 sum += 128 - abs((int)v - 128);
2513 sum += (v < 128) ? v : 256 - v;
2516 if (sum > lmins) /* We are already worse, don't continue. */
2522 static void /* PRIVATE */
2523 png_setup_avg_row_only(png_structrp png_ptr, png_uint_32 bpp,
2526 png_bytep rp, dp, pp, lp;
2529 png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
2531 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2532 pp = png_ptr->prev_row + 1; i < bpp; i++)
2534 *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
2537 for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
2539 *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
2544 static size_t /* PRIVATE */
2545 png_setup_paeth_row(png_structrp png_ptr, png_uint_32 bpp,
2546 size_t row_bytes, size_t lmins)
2548 png_bytep rp, dp, pp, cp, lp;
2553 png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
2555 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2556 pp = png_ptr->prev_row + 1; i < bpp; i++)
2558 v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2561 sum += 128 - abs((int)v - 128);
2563 sum += (v < 128) ? v : 256 - v;
2567 for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
2570 int a, b, c, pa, pb, pc, p;
2584 pa = p < 0 ? -p : p;
2585 pb = pc < 0 ? -pc : pc;
2586 pc = (p + pc) < 0 ? -(p + pc) : p + pc;
2589 p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
2591 v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
2594 sum += 128 - abs((int)v - 128);
2596 sum += (v < 128) ? v : 256 - v;
2599 if (sum > lmins) /* We are already worse, don't continue. */
2605 static void /* PRIVATE */
2606 png_setup_paeth_row_only(png_structrp png_ptr, png_uint_32 bpp,
2609 png_bytep rp, dp, pp, cp, lp;
2612 png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
2614 for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2615 pp = png_ptr->prev_row + 1; i < bpp; i++)
2617 *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2620 for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
2623 int a, b, c, pa, pb, pc, p;
2637 pa = p < 0 ? -p : p;
2638 pb = pc < 0 ? -pc : pc;
2639 pc = (p + pc) < 0 ? -(p + pc) : p + pc;
2642 p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
2644 *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
2647 #endif /* WRITE_FILTER */
2650 png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
2652 #ifndef PNG_WRITE_FILTER_SUPPORTED
2653 png_write_filtered_row(png_ptr, png_ptr->row_buf, row_info->rowbytes+1);
2655 unsigned int filter_to_do = png_ptr->do_filter;
2660 size_t row_bytes = row_info->rowbytes;
2662 png_debug(1, "in png_write_find_filter");
2664 /* Find out how many bytes offset each pixel is */
2665 bpp = (row_info->pixel_depth + 7) >> 3;
2667 row_buf = png_ptr->row_buf;
2668 mins = PNG_SIZE_MAX - 256/* so we can detect potential overflow of the
2671 /* The prediction method we use is to find which method provides the
2672 * smallest value when summing the absolute values of the distances
2673 * from zero, using anything >= 128 as negative numbers. This is known
2674 * as the "minimum sum of absolute differences" heuristic. Other
2675 * heuristics are the "weighted minimum sum of absolute differences"
2676 * (experimental and can in theory improve compression), and the "zlib
2677 * predictive" method (not implemented yet), which does test compressions
2678 * of lines using different filter methods, and then chooses the
2679 * (series of) filter(s) that give minimum compressed data size (VERY
2680 * computationally expensive).
2682 * GRR 980525: consider also
2684 * (1) minimum sum of absolute differences from running average (i.e.,
2685 * keep running sum of non-absolute differences & count of bytes)
2686 * [track dispersion, too? restart average if dispersion too large?]
2688 * (1b) minimum sum of absolute differences from sliding average, probably
2689 * with window size <= deflate window (usually 32K)
2691 * (2) minimum sum of squared differences from zero or running average
2692 * (i.e., ~ root-mean-square approach)
2696 /* We don't need to test the 'no filter' case if this is the only filter
2697 * that has been chosen, as it doesn't actually do anything to the data.
2699 best_row = png_ptr->row_buf;
2701 if (PNG_SIZE_MAX/128 <= row_bytes)
2703 /* Overflow can occur in the calculation, just select the lowest set
2706 filter_to_do &= 0U-filter_to_do;
2708 else if ((filter_to_do & PNG_FILTER_NONE) != 0 &&
2709 filter_to_do != PNG_FILTER_NONE)
2711 /* Overflow not possible and multiple filters in the list, including the
2720 for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
2724 sum += 128 - abs((int)v - 128);
2726 sum += (v < 128) ? v : 256 - v;
2735 if (filter_to_do == PNG_FILTER_SUB)
2736 /* It's the only filter so no testing is needed */
2738 png_setup_sub_row_only(png_ptr, bpp, row_bytes);
2739 best_row = png_ptr->try_row;
2742 else if ((filter_to_do & PNG_FILTER_SUB) != 0)
2745 size_t lmins = mins;
2747 sum = png_setup_sub_row(png_ptr, bpp, row_bytes, lmins);
2752 best_row = png_ptr->try_row;
2753 if (png_ptr->tst_row != NULL)
2755 png_ptr->try_row = png_ptr->tst_row;
2756 png_ptr->tst_row = best_row;
2762 if (filter_to_do == PNG_FILTER_UP)
2764 png_setup_up_row_only(png_ptr, row_bytes);
2765 best_row = png_ptr->try_row;
2768 else if ((filter_to_do & PNG_FILTER_UP) != 0)
2771 size_t lmins = mins;
2773 sum = png_setup_up_row(png_ptr, row_bytes, lmins);
2778 best_row = png_ptr->try_row;
2779 if (png_ptr->tst_row != NULL)
2781 png_ptr->try_row = png_ptr->tst_row;
2782 png_ptr->tst_row = best_row;
2788 if (filter_to_do == PNG_FILTER_AVG)
2790 png_setup_avg_row_only(png_ptr, bpp, row_bytes);
2791 best_row = png_ptr->try_row;
2794 else if ((filter_to_do & PNG_FILTER_AVG) != 0)
2797 size_t lmins = mins;
2799 sum= png_setup_avg_row(png_ptr, bpp, row_bytes, lmins);
2804 best_row = png_ptr->try_row;
2805 if (png_ptr->tst_row != NULL)
2807 png_ptr->try_row = png_ptr->tst_row;
2808 png_ptr->tst_row = best_row;
2814 if (filter_to_do == PNG_FILTER_PAETH)
2816 png_setup_paeth_row_only(png_ptr, bpp, row_bytes);
2817 best_row = png_ptr->try_row;
2820 else if ((filter_to_do & PNG_FILTER_PAETH) != 0)
2823 size_t lmins = mins;
2825 sum = png_setup_paeth_row(png_ptr, bpp, row_bytes, lmins);
2829 best_row = png_ptr->try_row;
2830 if (png_ptr->tst_row != NULL)
2832 png_ptr->try_row = png_ptr->tst_row;
2833 png_ptr->tst_row = best_row;
2838 /* Do the actual writing of the filtered row data from the chosen filter. */
2839 png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
2841 #endif /* WRITE_FILTER */
2845 /* Do the actual writing of a previously filtered row. */
2847 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
2848 size_t full_row_length/*includes filter byte*/)
2850 png_debug(1, "in png_write_filtered_row");
2852 png_debug1(2, "filter = %d", filtered_row[0]);
2854 png_compress_IDAT(png_ptr, filtered_row, full_row_length, Z_NO_FLUSH);
2856 #ifdef PNG_WRITE_FILTER_SUPPORTED
2857 /* Swap the current and previous rows */
2858 if (png_ptr->prev_row != NULL)
2862 tptr = png_ptr->prev_row;
2863 png_ptr->prev_row = png_ptr->row_buf;
2864 png_ptr->row_buf = tptr;
2866 #endif /* WRITE_FILTER */
2868 /* Finish row - updates counters and flushes zlib if last row */
2869 png_write_finish_row(png_ptr);
2871 #ifdef PNG_WRITE_FLUSH_SUPPORTED
2872 png_ptr->flush_rows++;
2874 if (png_ptr->flush_dist > 0 &&
2875 png_ptr->flush_rows >= png_ptr->flush_dist)
2877 png_write_flush(png_ptr);
2879 #endif /* WRITE_FLUSH */
2882 #ifdef PNG_WRITE_APNG_SUPPORTED
2884 png_write_reset(png_structp png_ptr)
2886 png_ptr->row_number = 0;
2888 png_ptr->mode &= ~PNG_HAVE_IDAT;
2892 png_write_reinit(png_structp png_ptr, png_infop info_ptr,
2893 png_uint_32 width, png_uint_32 height)
2895 if (png_ptr->num_frames_written == 0 &&
2896 (width != png_ptr->first_frame_width ||
2897 height != png_ptr->first_frame_height))
2898 png_error(png_ptr, "width and/or height in the first frame's fcTL "
2899 "don't match the ones in IHDR");
2900 if (width > png_ptr->first_frame_width ||
2901 height > png_ptr->first_frame_height)
2902 png_error(png_ptr, "width and/or height for a frame greater than"
2903 "the ones in IHDR");
2905 png_set_IHDR(png_ptr, info_ptr, width, height,
2906 info_ptr->bit_depth, info_ptr->color_type,
2907 info_ptr->interlace_type, info_ptr->compression_type,
2908 info_ptr->filter_type);
2910 png_ptr->width = width;
2911 png_ptr->height = height;
2912 png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
2913 png_ptr->usr_width = png_ptr->width;
2915 #endif /* PNG_WRITE_APNG_SUPPORTED */