1 /* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* ***** BEGIN LICENSE BLOCK *****
3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
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15 * The Original Code is mozilla.org code.
17 * The Initial Developer of the Original Code is
18 * Netscape Communications Corporation.
19 * Portions created by the Initial Developer are Copyright (C) 1998
20 * the Initial Developer. All Rights Reserved.
23 * Chris Saari <saari@netscape.com>
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41 The Graphics Interchange Format(c) is the copyright property of CompuServe
42 Incorporated. Only CompuServe Incorporated is authorized to define, redefine,
43 enhance, alter, modify or change in any way the definition of the format.
45 CompuServe Incorporated hereby grants a limited, non-exclusive, royalty-free
46 license for the use of the Graphics Interchange Format(sm) in computer
47 software; computer software utilizing GIF(sm) must acknowledge ownership of the
48 Graphics Interchange Format and its Service Mark by CompuServe Incorporated, in
49 User and Technical Documentation. Computer software utilizing GIF, which is
50 distributed or may be distributed without User or Technical Documentation must
51 display to the screen or printer a message acknowledging ownership of the
52 Graphics Interchange Format and the Service Mark by CompuServe Incorporated; in
53 this case, the acknowledgement may be displayed in an opening screen or leading
54 banner, or a closing screen or trailing banner. A message such as the following
57 "The Graphics Interchange Format(c) is the Copyright property of
58 CompuServe Incorporated. GIF(sm) is a Service Mark property of
59 CompuServe Incorporated."
61 For further information, please contact :
63 CompuServe Incorporated
64 Graphics Technology Department
65 5000 Arlington Center Boulevard
69 CompuServe Incorporated maintains a mailing list with all those individuals and
70 organizations who wish to receive copies of this document when it is corrected
71 or revised. This service is offered free of charge; please provide us with your
76 #include "GIFImageReader.h"
79 #include "GIFImageDecoder.h"
80 #include "ImageSource.h"
82 using WebCore::GIFImageDecoder;
84 // Define the Mozilla macro setup so that we can leave the macros alone.
85 #define PR_BEGIN_MACRO do {
86 #define PR_END_MACRO } while (0)
89 * GETN(n, s) requests at least 'n' bytes available from 'q', at start of state 's'
91 * Note, the hold will never need to be bigger than 256 bytes to gather up in the hold,
92 * as each GIF block (except colormaps) can never be bigger than 256 bytes.
93 * Colormaps are directly copied in the resp. global_colormap or dynamically allocated local_colormap.
94 * So a fixed buffer in GIFImageReader is good enough.
95 * This buffer is only needed to copy left-over data from one GifWrite call to the next
99 bytes_to_consume = (n); \
103 /* Get a 16-bit value stored in little-endian format */
104 #define GETINT16(p) ((p)[1]<<8|(p)[0])
106 //******************************************************************************
107 // Send the data to the display front-end.
108 bool GIFImageReader::output_row()
110 GIFFrameReader* gs = frame_reader;
112 int drow_start, drow_end;
114 drow_start = drow_end = gs->irow;
117 * Haeberli-inspired hack for interlaced GIFs: Replicate lines while
118 * displaying to diminish the "venetian-blind" effect as the image is
119 * loaded. Adjust pixel vertical positions to avoid the appearance of the
120 * image crawling up the screen as successive passes are drawn.
122 if (gs->progressive_display && gs->interlaced && gs->ipass < 4) {
123 unsigned row_dup = 0, row_shift = 0;
142 drow_start -= row_shift;
143 drow_end = drow_start + row_dup;
145 /* Extend if bottom edge isn't covered because of the shift upward. */
146 if (((gs->height - 1) - drow_end) <= row_shift)
147 drow_end = gs->height - 1;
149 /* Clamp first and last rows to upper and lower edge of image. */
152 if ((unsigned)drow_end >= gs->height)
153 drow_end = gs->height - 1;
156 /* Protect against too much image data */
157 if ((unsigned)drow_start >= gs->height)
160 // CALLBACK: Let the client know we have decoded a row.
161 if (clientptr && frame_reader &&
162 !clientptr->haveDecodedRow(images_count - 1, frame_reader->rowbuf, frame_reader->rowend,
163 drow_start, drow_end - drow_start + 1,
164 gs->progressive_display && gs->interlaced && gs->ipass > 1))
167 gs->rowp = gs->rowbuf;
177 if (gs->irow >= gs->height) {
185 if (gs->irow >= gs->height) {
193 if (gs->irow >= gs->height) {
201 if (gs->irow >= gs->height){
210 } while (gs->irow > (gs->height - 1));
216 //******************************************************************************
217 /* Perform Lempel-Ziv-Welch decoding */
218 bool GIFImageReader::do_lzw(const unsigned char *q)
220 GIFFrameReader* gs = frame_reader;
226 const unsigned char *ch;
228 /* Copy all the decoder state variables into locals so the compiler
229 * won't worry about them being aliased. The locals will be homed
230 * back into the GIF decoder structure when we exit.
232 int avail = gs->avail;
235 int codesize = gs->codesize;
236 int codemask = gs->codemask;
237 int oldcode = gs->oldcode;
238 int clear_code = gs->clear_code;
239 unsigned char firstchar = gs->firstchar;
240 int datum = gs->datum;
243 gs->prefix = new unsigned short[MAX_BITS];
244 memset(gs->prefix, 0, MAX_BITS * sizeof(short));
247 unsigned short *prefix = gs->prefix;
248 unsigned char *stackp = gs->stackp;
249 unsigned char *suffix = gs->suffix;
250 unsigned char *stack = gs->stack;
251 unsigned char *rowp = gs->rowp;
252 unsigned char *rowend = gs->rowend;
253 unsigned rows_remaining = gs->rows_remaining;
263 rowp = frame_reader->rowp; \
264 if (!rows_remaining) \
268 for (ch = q; cnt-- > 0; ch++)
270 /* Feed the next byte into the decoder's 32-bit input buffer. */
271 datum += ((int) *ch) << bits;
274 /* Check for underflow of decoder's 32-bit input buffer. */
275 while (bits >= codesize)
277 /* Get the leading variable-length symbol from the data stream */
278 code = datum & codemask;
282 /* Reset the dictionary to its original state, if requested */
283 if (code == clear_code) {
284 codesize = gs->datasize + 1;
285 codemask = (1 << codesize) - 1;
286 avail = clear_code + 2;
291 /* Check for explicit end-of-stream code */
292 if (code == (clear_code + 1)) {
293 /* end-of-stream should only appear after all image data */
296 return clientptr ? clientptr->setFailed() : false;
300 *rowp++ = suffix[code];
304 firstchar = oldcode = code;
310 *stackp++ = firstchar;
313 if (stackp == stack + MAX_BITS)
314 return clientptr ? clientptr->setFailed() : false;
317 while (code >= clear_code)
319 if (code >= MAX_BITS || code == prefix[code])
320 return clientptr ? clientptr->setFailed() : false;
322 // Even though suffix[] only holds characters through suffix[avail - 1],
323 // allowing code >= avail here lets us be more tolerant of malformed
324 // data. As long as code < MAX_BITS, the only risk is a garbled image,
325 // which is no worse than refusing to display it.
326 *stackp++ = suffix[code];
329 if (stackp == stack + MAX_BITS)
330 return clientptr ? clientptr->setFailed() : false;
333 *stackp++ = firstchar = suffix[code];
335 /* Define a new codeword in the dictionary. */
337 prefix[avail] = oldcode;
338 suffix[avail] = firstchar;
341 /* If we've used up all the codewords of a given length
342 * increase the length of codewords by one bit, but don't
343 * exceed the specified maximum codeword size of 12 bits.
345 if (((avail & codemask) == 0) && (avail < 4096)) {
352 /* Copy the decoded data out to the scanline buffer. */
355 if (rowp == rowend) {
358 } while (stackp > stack);
364 /* Home the local copies of the GIF decoder state variables */
367 gs->codesize = codesize;
368 gs->codemask = codemask;
370 gs->oldcode = oldcode;
371 gs->firstchar = firstchar;
375 gs->rows_remaining = rows_remaining;
381 /******************************************************************************/
383 * process data arriving from the stream for the gif decoder
386 bool GIFImageReader::read(const unsigned char *buf, unsigned len,
387 GIFImageDecoder::GIFQuery query, unsigned haltAtFrame)
390 // No new data has come in since the last call, just ignore this call.
394 const unsigned char *q = buf;
396 // Add what we have so far to the block
397 // If previous call to me left something in the hold first complete current block
398 // Or if we are filling the colormaps, first complete the colormap
399 unsigned char* p = 0;
400 if (state == gif_global_colormap)
402 else if (state == gif_image_colormap)
403 p = frame_reader ? frame_reader->local_colormap : 0;
404 else if (bytes_in_hold)
409 if (p || (state == gif_global_colormap) || (state == gif_image_colormap)) {
410 // Add what we have sofar to the block
411 unsigned l = len < bytes_to_consume ? len : bytes_to_consume;
413 memcpy(p + bytes_in_hold, buf, l);
415 if (l < bytes_to_consume) {
416 // Not enough in 'buf' to complete current block, get more
418 bytes_to_consume -= l;
420 clientptr->decodingHalted(0);
423 // Reset hold buffer count
425 // Point 'q' to complete block in hold (or in colormap)
430 // 'q' is start of current to be processed block (hold, colormap or buf)
431 // 'bytes_to_consume' is number of bytes to consume from 'buf'
432 // 'buf' points to the bytes to be consumed from the input buffer
433 // 'len' is number of bytes left in input buffer from position 'buf'.
434 // At entrance of the for loop will 'buf' will be moved 'bytes_to_consume'
435 // to point to next buffer, 'len' is adjusted accordingly.
436 // So that next round in for loop, q gets pointed to the next buffer.
438 for (;len >= bytes_to_consume; q=buf) {
439 // Eat the current block from the buffer, q keeps pointed at current block
440 buf += bytes_to_consume;
441 len -= bytes_to_consume;
447 return false; // If do_lzw() encountered an error, it has already called
448 // clientptr->setFailed().
449 GETN(1, gif_sub_block);
454 /* Initialize LZW parser/decoder */
456 // Since we use a codesize of 1 more than the datasize, we need to ensure
457 // that our datasize is strictly less than the MAX_LZW_BITS value (12).
458 // This sets the largest possible codemask correctly at 4095.
459 if (datasize >= MAX_LZW_BITS)
460 return clientptr ? clientptr->setFailed() : false;
461 int clear_code = 1 << datasize;
462 if (clear_code >= MAX_BITS)
463 return clientptr ? clientptr->setFailed() : false;
466 frame_reader->datasize = datasize;
467 frame_reader->clear_code = clear_code;
468 frame_reader->avail = frame_reader->clear_code + 2;
469 frame_reader->oldcode = -1;
470 frame_reader->codesize = frame_reader->datasize + 1;
471 frame_reader->codemask = (1 << frame_reader->codesize) - 1;
473 frame_reader->datum = frame_reader->bits = 0;
475 /* init the tables */
476 if (!frame_reader->suffix)
477 frame_reader->suffix = new unsigned char[MAX_BITS];
478 // Clearing the whole suffix table lets us be more tolerant of bad data.
479 memset(frame_reader->suffix, 0, MAX_BITS);
480 for (int i = 0; i < frame_reader->clear_code; i++)
481 frame_reader->suffix[i] = i;
483 if (!frame_reader->stack)
484 frame_reader->stack = new unsigned char[MAX_BITS];
485 frame_reader->stackp = frame_reader->stack;
488 GETN(1, gif_sub_block);
492 /* All GIF files begin with "GIF87a" or "GIF89a" */
495 if (!strncmp((char*)q, "GIF89a", 6))
497 else if (!strncmp((char*)q, "GIF87a", 6))
500 return clientptr ? clientptr->setFailed() : false;
501 GETN(7, gif_global_header);
505 case gif_global_header:
507 /* This is the height and width of the "screen" or
508 * frame into which images are rendered. The
509 * individual images can be smaller than the
510 * screen size and located with an origin anywhere
514 screen_width = GETINT16(q);
515 screen_height = GETINT16(q + 2);
517 // CALLBACK: Inform the decoderplugin of our size.
518 if (clientptr && !clientptr->setSize(screen_width, screen_height))
521 screen_bgcolor = q[5];
522 global_colormap_size = 2<<(q[4]&0x07);
524 if ((q[4] & 0x80) && global_colormap_size > 0) { /* global map */
525 // Get the global colormap
526 const unsigned size = 3*global_colormap_size;
528 // Malloc the color map, but only if we're not just counting frames.
529 if (query != GIFImageDecoder::GIFFrameCountQuery)
530 global_colormap = new unsigned char[size];
533 // Use 'hold' pattern to get the global colormap
534 GETN(size, gif_global_colormap);
538 // Copy everything and go directly to gif_image_start.
540 memcpy(global_colormap, buf, size);
545 GETN(1, gif_image_start);
547 // q[6] = Pixel Aspect Ratio
549 // float aspect = (float)((q[6] + 15) / 64.0);
553 case gif_global_colormap:
554 // Everything is already copied into global_colormap
555 GETN(1, gif_image_start);
558 case gif_image_start:
560 if (*q == ';') { /* terminator */
565 if (*q == '!') { /* extension */
566 GETN(2, gif_extension);
570 /* If we get anything other than ',' (image separator), '!'
571 * (extension), or ';' (trailer), there is extraneous data
572 * between blocks. The GIF87a spec tells us to keep reading
573 * until we find an image separator, but GIF89a says such
574 * a file is corrupt. We follow GIF89a and bail out. */
576 return clientptr ? clientptr->setFailed() : false;
578 GETN(9, gif_image_header);
584 int len = count = q[1];
585 gstate es = gif_skip_block;
590 es = gif_control_extension;
594 // ignoring plain text extension
598 es = gif_application_extension;
602 es = gif_consume_comment;
609 GETN(1, gif_image_start);
613 case gif_consume_block:
615 GETN(1, gif_image_start);
617 GETN(*q, gif_skip_block);
621 GETN(1, gif_consume_block);
624 case gif_control_extension:
626 if (query != GIFImageDecoder::GIFFrameCountQuery) {
628 frame_reader = new GIFFrameReader();
633 frame_reader->tpixel = q[3];
634 frame_reader->is_transparent = true;
636 frame_reader->is_transparent = false;
637 // ignoring gfx control extension
639 // NOTE: This relies on the values in the FrameDisposalMethod enum
640 // matching those in the GIF spec!
641 frame_reader->disposal_method = (WebCore::ImageFrame::FrameDisposalMethod)(((*q) >> 2) & 0x7);
642 // Some specs say 3rd bit (value 4), other specs say value 3
643 // Let's choose 3 (the more popular)
644 if (frame_reader->disposal_method == 4)
645 frame_reader->disposal_method = WebCore::ImageFrame::DisposeOverwritePrevious;
646 frame_reader->delay_time = GETINT16(q + 1) * 10;
648 GETN(1, gif_consume_block);
652 case gif_comment_extension:
655 GETN(*q, gif_consume_comment);
657 GETN(1, gif_image_start);
661 case gif_consume_comment:
662 GETN(1, gif_comment_extension);
665 case gif_application_extension:
666 /* Check for netscape application extension */
667 if (!strncmp((char*)q, "NETSCAPE2.0", 11) ||
668 !strncmp((char*)q, "ANIMEXTS1.0", 11))
669 GETN(1, gif_netscape_extension_block);
671 GETN(1, gif_consume_block);
674 /* Netscape-specific GIF extension: animation looping */
675 case gif_netscape_extension_block:
677 GETN(*q, gif_consume_netscape_extension);
679 GETN(1, gif_image_start);
682 /* Parse netscape-specific application extensions */
683 case gif_consume_netscape_extension:
685 int netscape_extension = q[0] & 7;
687 /* Loop entire animation specified # of times. Only read the
688 loop count during the first iteration. */
689 if (netscape_extension == 1) {
690 loop_count = GETINT16(q + 1);
692 /* Zero loop count is infinite animation loop request */
694 loop_count = WebCore::cAnimationLoopInfinite;
696 GETN(1, gif_netscape_extension_block);
698 /* Wait for specified # of bytes to enter buffer */
699 else if (netscape_extension == 2) {
700 // Don't do this, this extension doesn't exist (isn't used at all)
701 // and doesn't do anything, as our streaming/buffering takes care of it all...
702 // See: http://semmix.pl/color/exgraf/eeg24.htm
703 GETN(1, gif_netscape_extension_block);
705 // 0,3-7 are yet to be defined netscape extension codes
706 return clientptr ? clientptr->setFailed() : false;
712 case gif_image_header:
714 unsigned height, width, x_offset, y_offset;
716 /* Get image offsets, with respect to the screen origin */
717 x_offset = GETINT16(q);
718 y_offset = GETINT16(q + 2);
720 /* Get image width and height. */
721 width = GETINT16(q + 4);
722 height = GETINT16(q + 6);
724 /* Work around broken GIF files where the logical screen
725 * size has weird width or height. We assume that GIF87a
726 * files don't contain animations.
728 if ((images_decoded == 0) &&
729 ((screen_height < height) || (screen_width < width) ||
732 screen_height = height;
733 screen_width = width;
737 // CALLBACK: Inform the decoderplugin of our size.
738 if (clientptr && !clientptr->setSize(screen_width, screen_height))
742 /* Work around more broken GIF files that have zero image
744 if (!height || !width) {
745 height = screen_height;
746 width = screen_width;
747 if (!height || !width)
748 return clientptr ? clientptr->setFailed() : false;
751 if (query == GIFImageDecoder::GIFSizeQuery || haltAtFrame == images_decoded) {
752 // The decoder needs to stop. Hand back the number of bytes we consumed from
753 // buffer minus 9 (the amount we consumed to read the header).
755 clientptr->decodingHalted(len + 9);
756 GETN(9, gif_image_header);
760 images_count = images_decoded + 1;
762 if (query == GIFImageDecoder::GIFFullQuery && !frame_reader)
763 frame_reader = new GIFFrameReader();
766 frame_reader->x_offset = x_offset;
767 frame_reader->y_offset = y_offset;
768 frame_reader->height = height;
769 frame_reader->width = width;
771 /* This case will never be taken if this is the first image */
772 /* being decoded. If any of the later images are larger */
773 /* than the screen size, we need to reallocate buffers. */
774 if (screen_width < width) {
777 delete []frame_reader->rowbuf;
778 screen_width = width;
779 frame_reader->rowbuf = new unsigned char[screen_width];
780 } else if (!frame_reader->rowbuf) {
781 frame_reader->rowbuf = new unsigned char[screen_width];
784 if (!frame_reader->rowbuf)
785 return clientptr ? clientptr->setFailed() : false;
786 if (screen_height < height)
787 screen_height = height;
790 frame_reader->interlaced = true;
791 frame_reader->ipass = 1;
793 frame_reader->interlaced = false;
794 frame_reader->ipass = 0;
797 if (images_decoded == 0) {
798 frame_reader->progressive_display = true;
800 /* Overlaying interlaced, transparent GIFs over
801 existing image data using the Haeberli display hack
802 requires saving the underlying image in order to
803 avoid jaggies at the transparency edges. We are
804 unprepared to deal with that, so don't display such
805 images progressively */
806 frame_reader->progressive_display = false;
809 /* Clear state from last image */
810 frame_reader->irow = 0;
811 frame_reader->rows_remaining = frame_reader->height;
812 frame_reader->rowend = frame_reader->rowbuf + frame_reader->width;
813 frame_reader->rowp = frame_reader->rowbuf;
815 /* bits per pixel is q[8]&0x07 */
818 if (q[8] & 0x80) /* has a local colormap? */
820 int num_colors = 2 << (q[8] & 0x7);
821 const unsigned size = 3*num_colors;
822 unsigned char *map = frame_reader ? frame_reader->local_colormap : 0;
823 if (frame_reader && (!map || (num_colors > frame_reader->local_colormap_size))) {
825 map = new unsigned char[size];
827 return clientptr ? clientptr->setFailed() : false;
830 /* Switch to the new local palette after it loads */
832 frame_reader->local_colormap = map;
833 frame_reader->local_colormap_size = num_colors;
834 frame_reader->is_local_colormap_defined = true;
838 // Use 'hold' pattern to get the image colormap
839 GETN(size, gif_image_colormap);
842 // Copy everything and directly go to gif_lzw_start
844 memcpy(frame_reader->local_colormap, buf, size);
847 } else if (frame_reader) {
848 /* Switch back to the global palette */
849 frame_reader->is_local_colormap_defined = false;
851 GETN(1, gif_lzw_start);
855 case gif_image_colormap:
856 // Everything is already copied into local_colormap
857 GETN(1, gif_lzw_start);
862 if ((count = *q) != 0)
863 /* Still working on the same image: Process next LZW data block */
865 /* Make sure there are still rows left. If the GIF data */
866 /* is corrupt, we may not get an explicit terminator. */
867 if (frame_reader && frame_reader->rows_remaining == 0) {
868 /* This is an illegal GIF, but we remain tolerant. */
869 GETN(1, gif_sub_block);
871 GETN(count, gif_lzw);
874 /* See if there are any more images in this sequence. */
878 // CALLBACK: The frame is now complete.
879 if (clientptr && frame_reader && !clientptr->frameComplete(images_decoded - 1, frame_reader->delay_time, frame_reader->disposal_method))
880 return false; // frameComplete() has already called
881 // clientptr->setFailed().
883 /* Clear state from this image */
885 frame_reader->is_local_colormap_defined = false;
886 frame_reader->is_transparent = false;
889 GETN(1, gif_image_start);
895 // When the GIF is done, we can stop.
897 clientptr->gifComplete();
900 // We shouldn't ever get here.
906 // Copy the leftover into gs->hold
909 // Add what we have sofar to the block
911 if (state == gif_global_colormap)
913 else if (state == gif_image_colormap)
914 p = frame_reader ? frame_reader->local_colormap : 0;
919 bytes_to_consume -= len;
923 clientptr->decodingHalted(0);