4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1991-1997, Thomas G. Lane.
6 * Modified 2019 by Guido Vollbeding.
7 * libjpeg-turbo Modifications:
8 * Copyright (C) 2021-2022, D. R. Commander.
9 * For conditions of distribution and use, see the accompanying README.ijg
12 * This file contains routines to read input images in GIF format.
14 * These routines may need modification for non-Unix environments or
15 * specialized applications. As they stand, they assume input from
16 * an ordinary stdio stream. They further assume that reading begins
17 * at the start of the file; start_input may need work if the
18 * user interface has already read some data (e.g., to determine that
19 * the file is indeed GIF format).
23 * This code is loosely based on giftoppm from the PBMPLUS distribution
24 * of Feb. 1991. That file contains the following copyright notice:
25 * +-------------------------------------------------------------------+
26 * | Copyright 1990, David Koblas. |
27 * | Permission to use, copy, modify, and distribute this software |
28 * | and its documentation for any purpose and without fee is hereby |
29 * | granted, provided that the above copyright notice appear in all |
30 * | copies and that both that copyright notice and this permission |
31 * | notice appear in supporting documentation. This software is |
32 * | provided "as is" without express or implied warranty. |
33 * +-------------------------------------------------------------------+
36 #include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */
37 #include "jsamplecomp.h"
39 #if defined(GIF_SUPPORTED) && \
40 (BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED))
43 /* Macros to deal with unsigned chars as efficiently as compiler allows */
45 typedef unsigned char U_CHAR;
46 #define UCH(x) ((int)(x))
49 #define ReadOK(file, buffer, len) \
50 (fread(buffer, 1, len, file) == ((size_t)(len)))
53 #define MAXCOLORMAPSIZE 256 /* max # of colors in a GIF colormap */
54 #define NUMCOLORS 3 /* # of colors */
55 #define CM_RED 0 /* color component numbers */
59 #define MAX_LZW_BITS 12 /* maximum LZW code size */
60 #define LZW_TABLE_SIZE (1 << MAX_LZW_BITS) /* # of possible LZW symbols */
62 /* Macros for extracting header data --- note we assume chars may be signed */
64 #define LM_to_uint(array, offset) \
65 ((unsigned int)UCH(array[offset]) + \
66 (((unsigned int)UCH(array[offset + 1])) << 8))
68 #define BitSet(byte, bit) ((byte) & (bit))
69 #define INTERLACE 0x40 /* mask for bit signifying interlaced image */
70 #define COLORMAPFLAG 0x80 /* mask for bit signifying colormap presence */
74 * LZW decompression tables look like this:
75 * symbol_head[K] = prefix symbol of any LZW symbol K (0..LZW_TABLE_SIZE-1)
76 * symbol_tail[K] = suffix byte of any LZW symbol K (0..LZW_TABLE_SIZE-1)
77 * Note that entries 0..end_code of the above tables are not used,
78 * since those symbols represent raw bytes or special codes.
80 * The stack represents the not-yet-used expansion of the last LZW symbol.
81 * In the worst case, a symbol could expand to as many bytes as there are
82 * LZW symbols, so we allocate LZW_TABLE_SIZE bytes for the stack.
83 * (This is conservative since that number includes the raw-byte symbols.)
87 /* Private version of data source object */
90 struct cjpeg_source_struct pub; /* public fields */
92 j_compress_ptr cinfo; /* back link saves passing separate parm */
94 _JSAMPARRAY colormap; /* GIF colormap (converted to my format) */
96 /* State for GetCode and LZWReadByte */
97 U_CHAR code_buf[256 + 4]; /* current input data block */
98 int last_byte; /* # of bytes in code_buf */
99 int last_bit; /* # of bits in code_buf */
100 int cur_bit; /* next bit index to read */
101 boolean first_time; /* flags first call to GetCode */
102 boolean out_of_blocks; /* TRUE if hit terminator data block */
104 int input_code_size; /* codesize given in GIF file */
105 int clear_code, end_code; /* values for Clear and End codes */
107 int code_size; /* current actual code size */
108 int limit_code; /* 2^code_size */
109 int max_code; /* first unused code value */
111 /* Private state for LZWReadByte */
112 int oldcode; /* previous LZW symbol */
113 int firstcode; /* first byte of oldcode's expansion */
115 /* LZW symbol table and expansion stack */
116 UINT16 *symbol_head; /* => table of prefix symbols */
117 UINT8 *symbol_tail; /* => table of suffix bytes */
118 UINT8 *symbol_stack; /* => stack for symbol expansions */
119 UINT8 *sp; /* stack pointer */
121 /* State for interlaced image processing */
122 boolean is_interlaced; /* TRUE if have interlaced image */
123 jvirt_sarray_ptr interlaced_image; /* full image in interlaced order */
124 JDIMENSION cur_row_number; /* need to know actual row number */
125 JDIMENSION pass2_offset; /* # of pixel rows in pass 1 */
126 JDIMENSION pass3_offset; /* # of pixel rows in passes 1&2 */
127 JDIMENSION pass4_offset; /* # of pixel rows in passes 1,2,3 */
130 typedef gif_source_struct *gif_source_ptr;
133 /* Forward declarations */
134 METHODDEF(JDIMENSION) get_pixel_rows(j_compress_ptr cinfo,
135 cjpeg_source_ptr sinfo);
136 METHODDEF(JDIMENSION) load_interlaced_image(j_compress_ptr cinfo,
137 cjpeg_source_ptr sinfo);
138 METHODDEF(JDIMENSION) get_interlaced_row(j_compress_ptr cinfo,
139 cjpeg_source_ptr sinfo);
143 ReadByte(gif_source_ptr sinfo)
144 /* Read next byte from GIF file */
146 register FILE *infile = sinfo->pub.input_file;
149 if ((c = getc(infile)) == EOF)
150 ERREXIT(sinfo->cinfo, JERR_INPUT_EOF);
156 GetDataBlock(gif_source_ptr sinfo, U_CHAR *buf)
157 /* Read a GIF data block, which has a leading count byte */
158 /* A zero-length block marks the end of a data block sequence */
162 count = ReadByte(sinfo);
164 if (!ReadOK(sinfo->pub.input_file, buf, count))
165 ERREXIT(sinfo->cinfo, JERR_INPUT_EOF);
172 SkipDataBlocks(gif_source_ptr sinfo)
173 /* Skip a series of data blocks, until a block terminator is found */
177 while (GetDataBlock(sinfo, buf) > 0)
183 ReInitLZW(gif_source_ptr sinfo)
184 /* (Re)initialize LZW state; shared code for startup and Clear processing */
186 sinfo->code_size = sinfo->input_code_size + 1;
187 sinfo->limit_code = sinfo->clear_code << 1; /* 2^code_size */
188 sinfo->max_code = sinfo->clear_code + 2; /* first unused code value */
189 sinfo->sp = sinfo->symbol_stack; /* init stack to empty */
194 InitLZWCode(gif_source_ptr sinfo)
195 /* Initialize for a series of LZWReadByte (and hence GetCode) calls */
197 /* GetCode initialization */
198 sinfo->last_byte = 2; /* make safe to "recopy last two bytes" */
199 sinfo->code_buf[0] = 0;
200 sinfo->code_buf[1] = 0;
201 sinfo->last_bit = 0; /* nothing in the buffer */
202 sinfo->cur_bit = 0; /* force buffer load on first call */
203 sinfo->first_time = TRUE;
204 sinfo->out_of_blocks = FALSE;
206 /* LZWReadByte initialization: */
207 /* compute special code values (note that these do not change later) */
208 sinfo->clear_code = 1 << sinfo->input_code_size;
209 sinfo->end_code = sinfo->clear_code + 1;
215 GetCode(gif_source_ptr sinfo)
216 /* Fetch the next code_size bits from the GIF data */
217 /* We assume code_size is less than 16 */
222 while (sinfo->cur_bit + sinfo->code_size > sinfo->last_bit) {
223 /* Time to reload the buffer */
224 /* First time, share code with Clear case */
225 if (sinfo->first_time) {
226 sinfo->first_time = FALSE;
227 return sinfo->clear_code;
229 if (sinfo->out_of_blocks) {
230 WARNMS(sinfo->cinfo, JWRN_GIF_NOMOREDATA);
231 return sinfo->end_code; /* fake something useful */
233 /* preserve last two bytes of what we have -- assume code_size <= 16 */
234 sinfo->code_buf[0] = sinfo->code_buf[sinfo->last_byte-2];
235 sinfo->code_buf[1] = sinfo->code_buf[sinfo->last_byte-1];
236 /* Load more bytes; set flag if we reach the terminator block */
237 if ((count = GetDataBlock(sinfo, &sinfo->code_buf[2])) == 0) {
238 sinfo->out_of_blocks = TRUE;
239 WARNMS(sinfo->cinfo, JWRN_GIF_NOMOREDATA);
240 return sinfo->end_code; /* fake something useful */
243 sinfo->cur_bit = (sinfo->cur_bit - sinfo->last_bit) + 16;
244 sinfo->last_byte = 2 + count;
245 sinfo->last_bit = sinfo->last_byte * 8;
248 /* Form up next 24 bits in accum */
249 offs = sinfo->cur_bit >> 3; /* byte containing cur_bit */
250 accum = UCH(sinfo->code_buf[offs + 2]);
252 accum |= UCH(sinfo->code_buf[offs + 1]);
254 accum |= UCH(sinfo->code_buf[offs]);
256 /* Right-align cur_bit in accum, then mask off desired number of bits */
257 accum >>= (sinfo->cur_bit & 7);
258 sinfo->cur_bit += sinfo->code_size;
259 return accum & ((1 << sinfo->code_size) - 1);
264 LZWReadByte(gif_source_ptr sinfo)
265 /* Read an LZW-compressed byte */
267 register int code; /* current working code */
268 int incode; /* saves actual input code */
270 /* If any codes are stacked from a previously read symbol, return them */
271 if (sinfo->sp > sinfo->symbol_stack)
272 return (int)(*(--sinfo->sp));
274 /* Time to read a new symbol */
275 code = GetCode(sinfo);
277 if (code == sinfo->clear_code) {
278 /* Reinit state, swallow any extra Clear codes, and */
279 /* return next code, which is expected to be a raw byte. */
282 code = GetCode(sinfo);
283 } while (code == sinfo->clear_code);
284 if (code > sinfo->clear_code) { /* make sure it is a raw byte */
285 WARNMS(sinfo->cinfo, JWRN_GIF_BADDATA);
286 code = 0; /* use something valid */
288 /* make firstcode, oldcode valid! */
289 sinfo->firstcode = sinfo->oldcode = code;
293 if (code == sinfo->end_code) {
294 /* Skip the rest of the image, unless GetCode already read terminator */
295 if (!sinfo->out_of_blocks) {
296 SkipDataBlocks(sinfo);
297 sinfo->out_of_blocks = TRUE;
299 /* Complain that there's not enough data */
300 WARNMS(sinfo->cinfo, JWRN_GIF_ENDCODE);
301 /* Pad data with 0's */
302 return 0; /* fake something usable */
305 /* Got normal raw byte or LZW symbol */
306 incode = code; /* save for a moment */
308 if (code >= sinfo->max_code) { /* special case for not-yet-defined symbol */
309 /* code == max_code is OK; anything bigger is bad data */
310 if (code > sinfo->max_code) {
311 WARNMS(sinfo->cinfo, JWRN_GIF_BADDATA);
312 incode = 0; /* prevent creation of loops in symbol table */
314 /* this symbol will be defined as oldcode/firstcode */
315 *(sinfo->sp++) = (UINT8)sinfo->firstcode;
316 code = sinfo->oldcode;
319 /* If it's a symbol, expand it into the stack */
320 while (code >= sinfo->clear_code) {
321 *(sinfo->sp++) = sinfo->symbol_tail[code]; /* tail is a byte value */
322 code = sinfo->symbol_head[code]; /* head is another LZW symbol */
324 /* At this point code just represents a raw byte */
325 sinfo->firstcode = code; /* save for possible future use */
327 /* If there's room in table... */
328 if ((code = sinfo->max_code) < LZW_TABLE_SIZE) {
329 /* Define a new symbol = prev sym + head of this sym's expansion */
330 sinfo->symbol_head[code] = (UINT16)sinfo->oldcode;
331 sinfo->symbol_tail[code] = (UINT8)sinfo->firstcode;
333 /* Is it time to increase code_size? */
334 if (sinfo->max_code >= sinfo->limit_code &&
335 sinfo->code_size < MAX_LZW_BITS) {
337 sinfo->limit_code <<= 1; /* keep equal to 2^code_size */
341 sinfo->oldcode = incode; /* save last input symbol for future use */
342 return sinfo->firstcode; /* return first byte of symbol's expansion */
347 ReadColorMap(gif_source_ptr sinfo, int cmaplen, _JSAMPARRAY cmap)
348 /* Read a GIF colormap */
352 for (i = 0; i < cmaplen; i++) {
353 #if BITS_IN_JSAMPLE == 8
354 #define UPSCALE(x) (x)
356 #define UPSCALE(x) ((x) << (BITS_IN_JSAMPLE - 8))
358 cmap[CM_RED][i] = (_JSAMPLE)UPSCALE(ReadByte(sinfo));
359 cmap[CM_GREEN][i] = (_JSAMPLE)UPSCALE(ReadByte(sinfo));
360 cmap[CM_BLUE][i] = (_JSAMPLE)UPSCALE(ReadByte(sinfo));
361 if (cmap[CM_RED][i] != cmap[CM_GREEN][i] ||
362 cmap[CM_GREEN][i] != cmap[CM_BLUE][i])
366 if (sinfo->cinfo->in_color_space == JCS_RGB && gray) {
367 sinfo->cinfo->in_color_space = JCS_GRAYSCALE;
368 sinfo->cinfo->input_components = 1;
374 DoExtension(gif_source_ptr sinfo)
375 /* Process an extension block */
376 /* Currently we ignore 'em all */
380 /* Read extension label byte */
381 extlabel = ReadByte(sinfo);
382 TRACEMS1(sinfo->cinfo, 1, JTRC_GIF_EXTENSION, extlabel);
383 /* Skip the data block(s) associated with the extension */
384 SkipDataBlocks(sinfo);
389 * Read the file header; return image size and component count.
393 start_input_gif(j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
395 gif_source_ptr source = (gif_source_ptr)sinfo;
396 U_CHAR hdrbuf[10]; /* workspace for reading control blocks */
397 unsigned int width, height; /* image dimensions */
398 int colormaplen, aspectRatio;
401 /* Read and verify GIF Header */
402 if (!ReadOK(source->pub.input_file, hdrbuf, 6))
403 ERREXIT(cinfo, JERR_GIF_NOT);
404 if (hdrbuf[0] != 'G' || hdrbuf[1] != 'I' || hdrbuf[2] != 'F')
405 ERREXIT(cinfo, JERR_GIF_NOT);
406 /* Check for expected version numbers.
407 * If unknown version, give warning and try to process anyway;
408 * this is per recommendation in GIF89a standard.
410 if ((hdrbuf[3] != '8' || hdrbuf[4] != '7' || hdrbuf[5] != 'a') &&
411 (hdrbuf[3] != '8' || hdrbuf[4] != '9' || hdrbuf[5] != 'a'))
412 TRACEMS3(cinfo, 1, JTRC_GIF_BADVERSION, hdrbuf[3], hdrbuf[4], hdrbuf[5]);
414 /* Read and decipher Logical Screen Descriptor */
415 if (!ReadOK(source->pub.input_file, hdrbuf, 7))
416 ERREXIT(cinfo, JERR_INPUT_EOF);
417 width = LM_to_uint(hdrbuf, 0);
418 height = LM_to_uint(hdrbuf, 2);
419 if (width == 0 || height == 0)
420 ERREXIT(cinfo, JERR_GIF_EMPTY);
421 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
422 if (sinfo->max_pixels &&
423 (unsigned long long)width * height > sinfo->max_pixels)
424 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
426 /* we ignore the color resolution, sort flag, and background color index */
427 aspectRatio = UCH(hdrbuf[6]);
428 if (aspectRatio != 0 && aspectRatio != 49)
429 TRACEMS(cinfo, 1, JTRC_GIF_NONSQUARE);
431 /* Allocate space to store the colormap */
432 source->colormap = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
433 ((j_common_ptr)cinfo, JPOOL_IMAGE, (JDIMENSION)MAXCOLORMAPSIZE,
434 (JDIMENSION)NUMCOLORS);
435 colormaplen = 0; /* indicate initialization */
437 /* Read global colormap if header indicates it is present */
438 if (BitSet(hdrbuf[4], COLORMAPFLAG)) {
439 colormaplen = 2 << (hdrbuf[4] & 0x07);
440 ReadColorMap(source, colormaplen, source->colormap);
443 /* Scan until we reach start of desired image.
444 * We don't currently support skipping images, but could add it easily.
447 c = ReadByte(source);
449 if (c == ';') /* GIF terminator?? */
450 ERREXIT(cinfo, JERR_GIF_IMAGENOTFOUND);
452 if (c == '!') { /* Extension */
457 if (c != ',') { /* Not an image separator? */
458 WARNMS1(cinfo, JWRN_GIF_CHAR, c);
462 /* Read and decipher Local Image Descriptor */
463 if (!ReadOK(source->pub.input_file, hdrbuf, 9))
464 ERREXIT(cinfo, JERR_INPUT_EOF);
465 /* we ignore top/left position info, also sort flag */
466 width = LM_to_uint(hdrbuf, 4);
467 height = LM_to_uint(hdrbuf, 6);
468 if (width == 0 || height == 0)
469 ERREXIT(cinfo, JERR_GIF_EMPTY);
470 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
471 if (sinfo->max_pixels &&
472 (unsigned long long)width * height > sinfo->max_pixels)
473 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
475 source->is_interlaced = (BitSet(hdrbuf[8], INTERLACE) != 0);
477 /* Read local colormap if header indicates it is present */
478 /* Note: if we wanted to support skipping images, */
479 /* we'd need to skip rather than read colormap for ignored images */
480 if (BitSet(hdrbuf[8], COLORMAPFLAG)) {
481 colormaplen = 2 << (hdrbuf[8] & 0x07);
482 ReadColorMap(source, colormaplen, source->colormap);
485 source->input_code_size = ReadByte(source); /* get min-code-size byte */
486 if (source->input_code_size < 2 || source->input_code_size > 8)
487 ERREXIT1(cinfo, JERR_GIF_CODESIZE, source->input_code_size);
489 /* Reached desired image, so break out of loop */
490 /* If we wanted to skip this image, */
491 /* we'd call SkipDataBlocks and then continue the loop */
495 /* Prepare to read selected image: first initialize LZW decompressor */
496 source->symbol_head = (UINT16 *)
497 (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE,
498 LZW_TABLE_SIZE * sizeof(UINT16));
499 source->symbol_tail = (UINT8 *)
500 (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE,
501 LZW_TABLE_SIZE * sizeof(UINT8));
502 source->symbol_stack = (UINT8 *)
503 (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE,
504 LZW_TABLE_SIZE * sizeof(UINT8));
508 * If image is interlaced, we read it into a full-size sample array,
509 * decompressing as we go; then get_interlaced_row selects rows from the
510 * sample array in the proper order.
512 if (source->is_interlaced) {
513 /* We request the virtual array now, but can't access it until virtual
514 * arrays have been allocated. Hence, the actual work of reading the
515 * image is postponed until the first call to get_pixel_rows.
517 source->interlaced_image = (*cinfo->mem->request_virt_sarray)
518 ((j_common_ptr)cinfo, JPOOL_IMAGE, FALSE,
519 (JDIMENSION)width, (JDIMENSION)height, (JDIMENSION)1);
520 if (cinfo->progress != NULL) {
521 cd_progress_ptr progress = (cd_progress_ptr)cinfo->progress;
522 progress->total_extra_passes++; /* count file input as separate pass */
524 source->pub.get_pixel_rows = load_interlaced_image;
526 source->pub.get_pixel_rows = get_pixel_rows;
529 if (cinfo->in_color_space != JCS_GRAYSCALE) {
530 cinfo->in_color_space = JCS_RGB;
531 cinfo->input_components = NUMCOLORS;
534 /* Create compressor input buffer. */
535 source->pub._buffer = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
536 ((j_common_ptr)cinfo, JPOOL_IMAGE,
537 (JDIMENSION)width * cinfo->input_components, (JDIMENSION)1);
538 source->pub.buffer_height = 1;
540 /* Pad colormap for safety. */
541 for (c = colormaplen; c < source->clear_code; c++) {
542 source->colormap[CM_RED][c] =
543 source->colormap[CM_GREEN][c] =
544 source->colormap[CM_BLUE][c] = _CENTERJSAMPLE;
547 /* Return info about the image. */
548 cinfo->data_precision = BITS_IN_JSAMPLE; /* we always rescale data to this */
549 cinfo->image_width = width;
550 cinfo->image_height = height;
552 TRACEMS3(cinfo, 1, JTRC_GIF, width, height, colormaplen);
557 * Read one row of pixels.
558 * This version is used for noninterlaced GIF images:
559 * we read directly from the GIF file.
562 METHODDEF(JDIMENSION)
563 get_pixel_rows(j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
565 gif_source_ptr source = (gif_source_ptr)sinfo;
567 register _JSAMPROW ptr;
568 register JDIMENSION col;
569 register _JSAMPARRAY colormap = source->colormap;
571 ptr = source->pub._buffer[0];
572 if (cinfo->in_color_space == JCS_GRAYSCALE) {
573 for (col = cinfo->image_width; col > 0; col--) {
574 c = LZWReadByte(source);
575 *ptr++ = colormap[CM_RED][c];
578 for (col = cinfo->image_width; col > 0; col--) {
579 c = LZWReadByte(source);
580 *ptr++ = colormap[CM_RED][c];
581 *ptr++ = colormap[CM_GREEN][c];
582 *ptr++ = colormap[CM_BLUE][c];
590 * Read one row of pixels.
591 * This version is used for the first call on get_pixel_rows when
592 * reading an interlaced GIF file: we read the whole image into memory.
595 METHODDEF(JDIMENSION)
596 load_interlaced_image(j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
598 gif_source_ptr source = (gif_source_ptr)sinfo;
599 register _JSAMPROW sptr;
600 register JDIMENSION col;
602 cd_progress_ptr progress = (cd_progress_ptr)cinfo->progress;
604 /* Read the interlaced image into the virtual array we've created. */
605 for (row = 0; row < cinfo->image_height; row++) {
606 if (progress != NULL) {
607 progress->pub.pass_counter = (long)row;
608 progress->pub.pass_limit = (long)cinfo->image_height;
609 (*progress->pub.progress_monitor) ((j_common_ptr)cinfo);
611 sptr = *(_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
612 ((j_common_ptr)cinfo, source->interlaced_image, row, (JDIMENSION)1,
614 for (col = cinfo->image_width; col > 0; col--) {
615 *sptr++ = (_JSAMPLE)LZWReadByte(source);
618 if (progress != NULL)
619 progress->completed_extra_passes++;
621 /* Replace method pointer so subsequent calls don't come here. */
622 source->pub.get_pixel_rows = get_interlaced_row;
623 /* Initialize for get_interlaced_row, and perform first call on it. */
624 source->cur_row_number = 0;
625 source->pass2_offset = (cinfo->image_height + 7) / 8;
626 source->pass3_offset = source->pass2_offset + (cinfo->image_height + 3) / 8;
627 source->pass4_offset = source->pass3_offset + (cinfo->image_height + 1) / 4;
629 return get_interlaced_row(cinfo, sinfo);
634 * Read one row of pixels.
635 * This version is used for interlaced GIF images:
636 * we read from the virtual array.
639 METHODDEF(JDIMENSION)
640 get_interlaced_row(j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
642 gif_source_ptr source = (gif_source_ptr)sinfo;
644 register _JSAMPROW sptr, ptr;
645 register JDIMENSION col;
646 register _JSAMPARRAY colormap = source->colormap;
649 /* Figure out which row of interlaced image is needed, and access it. */
650 switch ((int)(source->cur_row_number & 7)) {
651 case 0: /* first-pass row */
652 irow = source->cur_row_number >> 3;
654 case 4: /* second-pass row */
655 irow = (source->cur_row_number >> 3) + source->pass2_offset;
657 case 2: /* third-pass row */
659 irow = (source->cur_row_number >> 2) + source->pass3_offset;
661 default: /* fourth-pass row */
662 irow = (source->cur_row_number >> 1) + source->pass4_offset;
664 sptr = *(_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
665 ((j_common_ptr)cinfo, source->interlaced_image, irow, (JDIMENSION)1,
667 /* Scan the row, expand colormap, and output */
668 ptr = source->pub._buffer[0];
669 if (cinfo->in_color_space == JCS_GRAYSCALE) {
670 for (col = cinfo->image_width; col > 0; col--) {
672 *ptr++ = colormap[CM_RED][c];
675 for (col = cinfo->image_width; col > 0; col--) {
677 *ptr++ = colormap[CM_RED][c];
678 *ptr++ = colormap[CM_GREEN][c];
679 *ptr++ = colormap[CM_BLUE][c];
682 source->cur_row_number++; /* for next time */
688 * Finish up at the end of the file.
692 finish_input_gif(j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
699 * The module selection routine for GIF format input.
702 GLOBAL(cjpeg_source_ptr)
703 _jinit_read_gif(j_compress_ptr cinfo)
705 gif_source_ptr source;
707 if (cinfo->data_precision != BITS_IN_JSAMPLE)
708 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
710 /* Create module interface object */
711 source = (gif_source_ptr)
712 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
713 sizeof(gif_source_struct));
714 source->cinfo = cinfo; /* make back link for subroutines */
715 /* Fill in method ptrs, except get_pixel_rows which start_input sets */
716 source->pub.start_input = start_input_gif;
717 source->pub.finish_input = finish_input_gif;
718 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
719 source->pub.max_pixels = 0;
722 return (cjpeg_source_ptr)source;
725 #endif /* defined(GIF_SUPPORTED) &&
726 (BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED)) */