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Unified Diff: third_party/gif/GIFImageReader.cpp

Issue 2445653004: Rename GIFImageReader to SkGifImageReader (Closed)
Patch Set: Remove dependent patch set Created 4 years, 2 months ago
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Index: third_party/gif/GIFImageReader.cpp
diff --git a/third_party/gif/GIFImageReader.cpp b/third_party/gif/GIFImageReader.cpp
deleted file mode 100644
index 859b45f7c4ccda3ee15137186e53a8bc3e06de52..0000000000000000000000000000000000000000
--- a/third_party/gif/GIFImageReader.cpp
+++ /dev/null
@@ -1,941 +0,0 @@
-/* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is mozilla.org code.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- * Chris Saari <saari@netscape.com>
- * Apple Computer
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
-
-/*
-The Graphics Interchange Format(c) is the copyright property of CompuServe
-Incorporated. Only CompuServe Incorporated is authorized to define, redefine,
-enhance, alter, modify or change in any way the definition of the format.
-
-CompuServe Incorporated hereby grants a limited, non-exclusive, royalty-free
-license for the use of the Graphics Interchange Format(sm) in computer
-software; computer software utilizing GIF(sm) must acknowledge ownership of the
-Graphics Interchange Format and its Service Mark by CompuServe Incorporated, in
-User and Technical Documentation. Computer software utilizing GIF, which is
-distributed or may be distributed without User or Technical Documentation must
-display to the screen or printer a message acknowledging ownership of the
-Graphics Interchange Format and the Service Mark by CompuServe Incorporated; in
-this case, the acknowledgement may be displayed in an opening screen or leading
-banner, or a closing screen or trailing banner. A message such as the following
-may be used:
-
- "The Graphics Interchange Format(c) is the Copyright property of
- CompuServe Incorporated. GIF(sm) is a Service Mark property of
- CompuServe Incorporated."
-
-For further information, please contact :
-
- CompuServe Incorporated
- Graphics Technology Department
- 5000 Arlington Center Boulevard
- Columbus, Ohio 43220
- U. S. A.
-
-CompuServe Incorporated maintains a mailing list with all those individuals and
-organizations who wish to receive copies of this document when it is corrected
-or revised. This service is offered free of charge; please provide us with your
-mailing address.
-*/
-
-#include "GIFImageReader.h"
-#include "SkColorPriv.h"
-#include "SkGifCodec.h"
-
-#include <algorithm>
-#include <string.h>
-
-
-// GETN(n, s) requests at least 'n' bytes available from 'q', at start of state 's'.
-//
-// Note, the hold will never need to be bigger than 256 bytes to gather up in the hold,
-// as each GIF block (except colormaps) can never be bigger than 256 bytes.
-// Colormaps are directly copied in the resp. global_colormap or dynamically allocated local_colormap.
-// So a fixed buffer in GIFImageReader is good enough.
-// This buffer is only needed to copy left-over data from one GifWrite call to the next
-#define GETN(n, s) \
- do { \
- m_bytesToConsume = (n); \
- m_state = (s); \
- } while (0)
-
-// Get a 16-bit value stored in little-endian format.
-#define GETINT16(p) ((p)[1]<<8|(p)[0])
-
-// Send the data to the display front-end.
-bool GIFLZWContext::outputRow(const unsigned char* rowBegin)
-{
- int drowStart = irow;
- int drowEnd = irow;
-
- // Haeberli-inspired hack for interlaced GIFs: Replicate lines while
- // displaying to diminish the "venetian-blind" effect as the image is
- // loaded. Adjust pixel vertical positions to avoid the appearance of the
- // image crawling up the screen as successive passes are drawn.
- if (m_frameContext->progressiveDisplay() && m_frameContext->interlaced() && ipass < 4) {
- unsigned rowDup = 0;
- unsigned rowShift = 0;
-
- switch (ipass) {
- case 1:
- rowDup = 7;
- rowShift = 3;
- break;
- case 2:
- rowDup = 3;
- rowShift = 1;
- break;
- case 3:
- rowDup = 1;
- rowShift = 0;
- break;
- default:
- break;
- }
-
- drowStart -= rowShift;
- drowEnd = drowStart + rowDup;
-
- // Extend if bottom edge isn't covered because of the shift upward.
- if (((m_frameContext->height() - 1) - drowEnd) <= rowShift)
- drowEnd = m_frameContext->height() - 1;
-
- // Clamp first and last rows to upper and lower edge of image.
- if (drowStart < 0)
- drowStart = 0;
-
- if ((unsigned)drowEnd >= m_frameContext->height())
- drowEnd = m_frameContext->height() - 1;
- }
-
- // Protect against too much image data.
- if ((unsigned)drowStart >= m_frameContext->height())
- return true;
-
- // CALLBACK: Let the client know we have decoded a row.
- if (!m_client->haveDecodedRow(m_frameContext->frameId(), rowBegin,
- drowStart, drowEnd - drowStart + 1, m_frameContext->progressiveDisplay() && m_frameContext->interlaced() && ipass > 1))
- return false;
-
- if (!m_frameContext->interlaced())
- irow++;
- else {
- do {
- switch (ipass) {
- case 1:
- irow += 8;
- if (irow >= m_frameContext->height()) {
- ipass++;
- irow = 4;
- }
- break;
-
- case 2:
- irow += 8;
- if (irow >= m_frameContext->height()) {
- ipass++;
- irow = 2;
- }
- break;
-
- case 3:
- irow += 4;
- if (irow >= m_frameContext->height()) {
- ipass++;
- irow = 1;
- }
- break;
-
- case 4:
- irow += 2;
- if (irow >= m_frameContext->height()) {
- ipass++;
- irow = 0;
- }
- break;
-
- default:
- break;
- }
- } while (irow > (m_frameContext->height() - 1));
- }
- return true;
-}
-
-// Perform Lempel-Ziv-Welch decoding.
-// Returns true if decoding was successful. In this case the block will have been completely consumed and/or rowsRemaining will be 0.
-// Otherwise, decoding failed; returns false in this case, which will always cause the GIFImageReader to set the "decode failed" flag.
-bool GIFLZWContext::doLZW(const unsigned char* block, size_t bytesInBlock)
-{
- const size_t width = m_frameContext->width();
-
- if (rowIter == rowBuffer.end())
- return true;
-
- for (const unsigned char* ch = block; bytesInBlock-- > 0; ch++) {
- // Feed the next byte into the decoder's 32-bit input buffer.
- datum += ((int) *ch) << bits;
- bits += 8;
-
- // Check for underflow of decoder's 32-bit input buffer.
- while (bits >= codesize) {
- // Get the leading variable-length symbol from the data stream.
- int code = datum & codemask;
- datum >>= codesize;
- bits -= codesize;
-
- // Reset the dictionary to its original state, if requested.
- if (code == clearCode) {
- codesize = m_frameContext->dataSize() + 1;
- codemask = (1 << codesize) - 1;
- avail = clearCode + 2;
- oldcode = -1;
- continue;
- }
-
- // Check for explicit end-of-stream code.
- if (code == (clearCode + 1)) {
- // end-of-stream should only appear after all image data.
- if (!rowsRemaining)
- return true;
- return false;
- }
-
- const int tempCode = code;
- unsigned short codeLength = 0;
- if (code < avail) {
- // This is a pre-existing code, so we already know what it
- // encodes.
- codeLength = suffixLength[code];
- rowIter += codeLength;
- } else if (code == avail && oldcode != -1) {
- // This is a new code just being added to the dictionary.
- // It must encode the contents of the previous code, plus
- // the first character of the previous code again.
- codeLength = suffixLength[oldcode] + 1;
- rowIter += codeLength;
- *--rowIter = firstchar;
- code = oldcode;
- } else {
- // This is an invalid code. The dictionary is just initialized
- // and the code is incomplete. We don't know how to handle
- // this case.
- return false;
- }
-
- while (code >= clearCode) {
- *--rowIter = suffix[code];
- code = prefix[code];
- }
-
- *--rowIter = firstchar = suffix[code];
-
- // Define a new codeword in the dictionary as long as we've read
- // more than one value from the stream.
- if (avail < MAX_DICTIONARY_ENTRIES && oldcode != -1) {
- prefix[avail] = oldcode;
- suffix[avail] = firstchar;
- suffixLength[avail] = suffixLength[oldcode] + 1;
- ++avail;
-
- // If we've used up all the codewords of a given length
- // increase the length of codewords by one bit, but don't
- // exceed the specified maximum codeword size.
- if (!(avail & codemask) && avail < MAX_DICTIONARY_ENTRIES) {
- ++codesize;
- codemask += avail;
- }
- }
- oldcode = tempCode;
- rowIter += codeLength;
-
- // Output as many rows as possible.
- unsigned char* rowBegin = rowBuffer.begin();
- for (; rowBegin + width <= rowIter; rowBegin += width) {
- if (!outputRow(rowBegin))
- return false;
- rowsRemaining--;
- if (!rowsRemaining)
- return true;
- }
-
- if (rowBegin != rowBuffer.begin()) {
- // Move the remaining bytes to the beginning of the buffer.
- const size_t bytesToCopy = rowIter - rowBegin;
- memcpy(&rowBuffer.front(), rowBegin, bytesToCopy);
- rowIter = rowBuffer.begin() + bytesToCopy;
- }
- }
- }
- return true;
-}
-
-sk_sp<SkColorTable> GIFColorMap::buildTable(SkColorType colorType, size_t transparentPixel) const
-{
- if (!m_isDefined)
- return nullptr;
-
- const PackColorProc proc = choose_pack_color_proc(false, colorType);
- if (m_table) {
- if (transparentPixel > (unsigned) m_table->count()
- || m_table->operator[](transparentPixel) == SK_ColorTRANSPARENT) {
- if (proc == m_packColorProc) {
- // This SkColorTable has already been built with the same transparent color and
- // packing proc. Reuse it.
- return m_table;
- }
- }
- }
- m_packColorProc = proc;
-
- SkASSERT(m_colors <= MAX_COLORS);
- const uint8_t* srcColormap = m_rawData->bytes();
- SkPMColor colorStorage[MAX_COLORS];
- for (size_t i = 0; i < m_colors; i++) {
- if (i == transparentPixel) {
- colorStorage[i] = SK_ColorTRANSPARENT;
- } else {
- colorStorage[i] = proc(255, srcColormap[0], srcColormap[1], srcColormap[2]);
- }
- srcColormap += BYTES_PER_COLORMAP_ENTRY;
- }
- for (size_t i = m_colors; i < MAX_COLORS; i++) {
- colorStorage[i] = SK_ColorTRANSPARENT;
- }
- m_table = sk_sp<SkColorTable>(new SkColorTable(colorStorage, MAX_COLORS));
- return m_table;
-}
-
-sk_sp<SkColorTable> GIFImageReader::getColorTable(SkColorType colorType, size_t index) const {
- if (index >= m_frames.size()) {
- return nullptr;
- }
-
- const GIFFrameContext* frameContext = m_frames[index].get();
- const GIFColorMap& localColorMap = frameContext->localColorMap();
- if (localColorMap.isDefined()) {
- return localColorMap.buildTable(colorType, frameContext->transparentPixel());
- }
- if (m_globalColorMap.isDefined()) {
- return m_globalColorMap.buildTable(colorType, frameContext->transparentPixel());
- }
- return nullptr;
-}
-
-// Perform decoding for this frame. frameComplete will be true if the entire frame is decoded.
-// Returns false if a decoding error occurred. This is a fatal error and causes the GIFImageReader to set the "decode failed" flag.
-// Otherwise, either not enough data is available to decode further than before, or the new data has been decoded successfully; returns true in this case.
-bool GIFFrameContext::decode(SkGifCodec* client, bool* frameComplete)
-{
- *frameComplete = false;
- if (!m_lzwContext) {
- // Wait for more data to properly initialize GIFLZWContext.
- if (!isDataSizeDefined() || !isHeaderDefined())
- return true;
-
- m_lzwContext.reset(new GIFLZWContext(client, this));
- if (!m_lzwContext->prepareToDecode()) {
- m_lzwContext.reset();
- return false;
- }
-
- m_currentLzwBlock = 0;
- }
-
- // Some bad GIFs have extra blocks beyond the last row, which we don't want to decode.
- while (m_currentLzwBlock < m_lzwBlocks.size() && m_lzwContext->hasRemainingRows()) {
- if (!m_lzwContext->doLZW(reinterpret_cast<const unsigned char*>(m_lzwBlocks[m_currentLzwBlock]->data()),
- m_lzwBlocks[m_currentLzwBlock]->size())) {
- return false;
- }
- ++m_currentLzwBlock;
- }
-
- // If this frame is data complete then the previous loop must have completely decoded all LZW blocks.
- // There will be no more decoding for this frame so it's time to cleanup.
- if (isComplete()) {
- *frameComplete = true;
- m_lzwContext.reset();
- }
- return true;
-}
-
-// Decode a frame.
-// This method uses GIFFrameContext:decode() to decode the frame; decoding error is reported to client as a critical failure.
-// Return true if decoding has progressed. Return false if an error has occurred.
-bool GIFImageReader::decode(size_t frameIndex, bool* frameComplete)
-{
- GIFFrameContext* currentFrame = m_frames[frameIndex].get();
-
- return currentFrame->decode(m_client, frameComplete);
-}
-
-// Parse incoming GIF data stream into internal data structures.
-// Return true if parsing has progressed or there is not enough data.
-// Return false if a fatal error is encountered.
-bool GIFImageReader::parse(GIFImageReader::GIFParseQuery query)
-{
- if (m_parseCompleted) {
- return true;
- }
-
- // GIFSizeQuery and GIFFrameCountQuery are negative, so this is only meaningful when >= 0.
- const int lastFrameToParse = (int) query;
- if (lastFrameToParse >= 0 && (int) m_frames.size() > lastFrameToParse
- && m_frames[lastFrameToParse]->isComplete()) {
- // We have already parsed this frame.
- return true;
- }
-
- while (true) {
- const size_t bytesBuffered = m_streamBuffer.buffer(m_bytesToConsume);
- if (bytesBuffered < m_bytesToConsume) {
- // The stream does not yet have enough data. Mark that we need less next time around,
- // and return.
- m_bytesToConsume -= bytesBuffered;
- return true;
- }
-
- switch (m_state) {
- case GIFLZW:
- SkASSERT(!m_frames.empty());
- // FIXME: All this copying might be wasteful for e.g. SkMemoryStream
- m_frames.back()->addLzwBlock(m_streamBuffer.get(), m_streamBuffer.bytesBuffered());
- GETN(1, GIFSubBlock);
- break;
-
- case GIFLZWStart: {
- SkASSERT(!m_frames.empty());
- m_frames.back()->setDataSize(this->getOneByte());
- GETN(1, GIFSubBlock);
- break;
- }
-
- case GIFType: {
- const char* currentComponent = m_streamBuffer.get();
-
- // All GIF files begin with "GIF87a" or "GIF89a".
- if (!memcmp(currentComponent, "GIF89a", 6))
- m_version = 89;
- else if (!memcmp(currentComponent, "GIF87a", 6))
- m_version = 87;
- else {
- // This prevents attempting to continue reading this invalid stream.
- GETN(0, GIFDone);
- return false;
- }
- GETN(7, GIFGlobalHeader);
- break;
- }
-
- case GIFGlobalHeader: {
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- // This is the height and width of the "screen" or frame into which
- // images are rendered. The individual images can be smaller than
- // the screen size and located with an origin anywhere within the
- // screen.
- // Note that we don't inform the client of the size yet, as it might
- // change after we read the first frame's image header.
- m_screenWidth = GETINT16(currentComponent);
- m_screenHeight = GETINT16(currentComponent + 2);
-
- const size_t globalColorMapColors = 2 << (currentComponent[4] & 0x07);
-
- if ((currentComponent[4] & 0x80) && globalColorMapColors > 0) { /* global map */
- m_globalColorMap.setNumColors(globalColorMapColors);
- GETN(BYTES_PER_COLORMAP_ENTRY * globalColorMapColors, GIFGlobalColormap);
- break;
- }
-
- GETN(1, GIFImageStart);
- break;
- }
-
- case GIFGlobalColormap: {
- m_globalColorMap.setRawData(m_streamBuffer.get(), m_streamBuffer.bytesBuffered());
- GETN(1, GIFImageStart);
- break;
- }
-
- case GIFImageStart: {
- const char currentComponent = m_streamBuffer.get()[0];
-
- if (currentComponent == '!') { // extension.
- GETN(2, GIFExtension);
- break;
- }
-
- if (currentComponent == ',') { // image separator.
- GETN(9, GIFImageHeader);
- break;
- }
-
- // If we get anything other than ',' (image separator), '!'
- // (extension), or ';' (trailer), there is extraneous data
- // between blocks. The GIF87a spec tells us to keep reading
- // until we find an image separator, but GIF89a says such
- // a file is corrupt. We follow Mozilla's implementation and
- // proceed as if the file were correctly terminated, so the
- // GIF will display.
- GETN(0, GIFDone);
- break;
- }
-
- case GIFExtension: {
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- size_t bytesInBlock = currentComponent[1];
- GIFState exceptionState = GIFSkipBlock;
-
- switch (*currentComponent) {
- case 0xf9:
- exceptionState = GIFControlExtension;
- // The GIF spec mandates that the GIFControlExtension header block length is 4 bytes,
- // and the parser for this block reads 4 bytes, so we must enforce that the buffer
- // contains at least this many bytes. If the GIF specifies a different length, we
- // allow that, so long as it's larger; the additional data will simply be ignored.
- bytesInBlock = std::max(bytesInBlock, static_cast<size_t>(4));
- break;
-
- // The GIF spec also specifies the lengths of the following two extensions' headers
- // (as 12 and 11 bytes, respectively). Because we ignore the plain text extension entirely
- // and sanity-check the actual length of the application extension header before reading it,
- // we allow GIFs to deviate from these values in either direction. This is important for
- // real-world compatibility, as GIFs in the wild exist with application extension headers
- // that are both shorter and longer than 11 bytes.
- case 0x01:
- // ignoring plain text extension
- break;
-
- case 0xff:
- exceptionState = GIFApplicationExtension;
- break;
-
- case 0xfe:
- exceptionState = GIFConsumeComment;
- break;
- }
-
- if (bytesInBlock)
- GETN(bytesInBlock, exceptionState);
- else
- GETN(1, GIFImageStart);
- break;
- }
-
- case GIFConsumeBlock: {
- const unsigned char currentComponent = this->getOneByte();
- if (!currentComponent)
- GETN(1, GIFImageStart);
- else
- GETN(currentComponent, GIFSkipBlock);
- break;
- }
-
- case GIFSkipBlock: {
- GETN(1, GIFConsumeBlock);
- break;
- }
-
- case GIFControlExtension: {
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- addFrameIfNecessary();
- GIFFrameContext* currentFrame = m_frames.back().get();
- if (*currentComponent & 0x1)
- currentFrame->setTransparentPixel(currentComponent[3]);
-
- // We ignore the "user input" bit.
-
- // NOTE: This relies on the values in the FrameDisposalMethod enum
- // matching those in the GIF spec!
- int rawDisposalMethod = ((*currentComponent) >> 2) & 0x7;
- switch (rawDisposalMethod) {
- case 1:
- case 2:
- case 3:
- currentFrame->setDisposalMethod((SkCodecAnimation::DisposalMethod) rawDisposalMethod);
- break;
- case 4:
- // Some specs say that disposal method 3 is "overwrite previous", others that setting
- // the third bit of the field (i.e. method 4) is. We map both to the same value.
- currentFrame->setDisposalMethod(SkCodecAnimation::RestorePrevious_DisposalMethod);
- break;
- default:
- // Other values use the default.
- currentFrame->setDisposalMethod(SkCodecAnimation::Keep_DisposalMethod);
- break;
- }
- currentFrame->setDelayTime(GETINT16(currentComponent + 1) * 10);
- GETN(1, GIFConsumeBlock);
- break;
- }
-
- case GIFCommentExtension: {
- const unsigned char currentComponent = this->getOneByte();
- if (currentComponent)
- GETN(currentComponent, GIFConsumeComment);
- else
- GETN(1, GIFImageStart);
- break;
- }
-
- case GIFConsumeComment: {
- GETN(1, GIFCommentExtension);
- break;
- }
-
- case GIFApplicationExtension: {
- // Check for netscape application extension.
- if (m_streamBuffer.bytesBuffered() == 11) {
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- if (!memcmp(currentComponent, "NETSCAPE2.0", 11) || !memcmp(currentComponent, "ANIMEXTS1.0", 11))
- GETN(1, GIFNetscapeExtensionBlock);
- }
-
- if (m_state != GIFNetscapeExtensionBlock)
- GETN(1, GIFConsumeBlock);
- break;
- }
-
- // Netscape-specific GIF extension: animation looping.
- case GIFNetscapeExtensionBlock: {
- const int currentComponent = this->getOneByte();
- // GIFConsumeNetscapeExtension always reads 3 bytes from the stream; we should at least wait for this amount.
- if (currentComponent)
- GETN(std::max(3, currentComponent), GIFConsumeNetscapeExtension);
- else
- GETN(1, GIFImageStart);
- break;
- }
-
- // Parse netscape-specific application extensions
- case GIFConsumeNetscapeExtension: {
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- int netscapeExtension = currentComponent[0] & 7;
-
- // Loop entire animation specified # of times. Only read the loop count during the first iteration.
- if (netscapeExtension == 1) {
- m_loopCount = GETINT16(currentComponent + 1);
-
- // Zero loop count is infinite animation loop request.
- if (!m_loopCount)
- m_loopCount = SkCodecAnimation::kAnimationLoopInfinite;
-
- GETN(1, GIFNetscapeExtensionBlock);
- } else if (netscapeExtension == 2) {
- // Wait for specified # of bytes to enter buffer.
-
- // Don't do this, this extension doesn't exist (isn't used at all)
- // and doesn't do anything, as our streaming/buffering takes care of it all...
- // See: http://semmix.pl/color/exgraf/eeg24.htm
- GETN(1, GIFNetscapeExtensionBlock);
- } else {
- // 0,3-7 are yet to be defined netscape extension codes
- // This prevents attempting to continue reading this invalid stream.
- GETN(0, GIFDone);
- return false;
- }
- break;
- }
-
- case GIFImageHeader: {
- unsigned height, width, xOffset, yOffset;
- const unsigned char* currentComponent =
- reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
-
- /* Get image offsets, with respect to the screen origin */
- xOffset = GETINT16(currentComponent);
- yOffset = GETINT16(currentComponent + 2);
-
- /* Get image width and height. */
- width = GETINT16(currentComponent + 4);
- height = GETINT16(currentComponent + 6);
-
- // Some GIF files have frames that don't fit in the specified
- // overall image size. For the first frame, we can simply enlarge
- // the image size to allow the frame to be visible. We can't do
- // this on subsequent frames because the rest of the decoding
- // infrastructure assumes the image size won't change as we
- // continue decoding, so any subsequent frames that are even
- // larger will be cropped.
- // Luckily, handling just the first frame is sufficient to deal
- // with most cases, e.g. ones where the image size is erroneously
- // set to zero, since usually the first frame completely fills
- // the image.
- if (currentFrameIsFirstFrame()) {
- m_screenHeight = std::max(m_screenHeight, yOffset + height);
- m_screenWidth = std::max(m_screenWidth, xOffset + width);
- }
-
- // NOTE: Chromium placed this block after setHeaderDefined, down
- // below we returned true when asked for the size. So Chromium
- // created an image which would fail. Is this the correct behavior?
- // We choose to return false early, so we will not create an
- // SkCodec.
-
- // Work around more broken GIF files that have zero image width or
- // height.
- if (!height || !width) {
- height = m_screenHeight;
- width = m_screenWidth;
- if (!height || !width) {
- // This prevents attempting to continue reading this invalid stream.
- GETN(0, GIFDone);
- return false;
- }
- }
-
- const bool isLocalColormapDefined = currentComponent[8] & 0x80;
- // The three low-order bits of currentComponent[8] specify the bits per pixel.
- const size_t numColors = 2 << (currentComponent[8] & 0x7);
- if (currentFrameIsFirstFrame()) {
- bool hasTransparentPixel;
- if (m_frames.size() == 0) {
- // We did not see a Graphics Control Extension, so no transparent
- // pixel was specified.
- hasTransparentPixel = false;
- } else {
- // This means we did see a Graphics Control Extension, which specifies
- // the transparent pixel
- const size_t transparentPixel = m_frames[0]->transparentPixel();
- if (isLocalColormapDefined) {
- hasTransparentPixel = transparentPixel < numColors;
- } else {
- const size_t globalColors = m_globalColorMap.numColors();
- if (!globalColors) {
- // No color table for this frame, so the frame is empty.
- // This is technically different from having a transparent
- // pixel, but we'll treat it the same - nothing to draw here.
- hasTransparentPixel = true;
- } else {
- hasTransparentPixel = transparentPixel < globalColors;
- }
- }
- }
-
- if (hasTransparentPixel) {
- m_firstFrameHasAlpha = true;
- m_firstFrameSupportsIndex8 = true;
- } else {
- const bool frameIsSubset = xOffset > 0 || yOffset > 0
- || xOffset + width < m_screenWidth
- || yOffset + height < m_screenHeight;
- m_firstFrameHasAlpha = frameIsSubset;
- m_firstFrameSupportsIndex8 = !frameIsSubset;
- }
- }
-
- if (query == GIFSizeQuery) {
- // The decoder needs to stop, so we return here, before
- // flushing the buffer. Next time through, we'll be in the same
- // state, requiring the same amount in the buffer.
- m_bytesToConsume = 0;
- return true;
- }
-
- addFrameIfNecessary();
- GIFFrameContext* currentFrame = m_frames.back().get();
-
- currentFrame->setHeaderDefined();
-
- currentFrame->setRect(xOffset, yOffset, width, height);
- currentFrame->setInterlaced(currentComponent[8] & 0x40);
-
- // Overlaying interlaced, transparent GIFs over
- // existing image data using the Haeberli display hack
- // requires saving the underlying image in order to
- // avoid jaggies at the transparency edges. We are
- // unprepared to deal with that, so don't display such
- // images progressively. Which means only the first
- // frame can be progressively displayed.
- // FIXME: It is possible that a non-transparent frame
- // can be interlaced and progressively displayed.
- currentFrame->setProgressiveDisplay(currentFrameIsFirstFrame());
-
- if (isLocalColormapDefined) {
- currentFrame->localColorMap().setNumColors(numColors);
- GETN(BYTES_PER_COLORMAP_ENTRY * numColors, GIFImageColormap);
- break;
- }
-
- GETN(1, GIFLZWStart);
- break;
- }
-
- case GIFImageColormap: {
- SkASSERT(!m_frames.empty());
- m_frames.back()->localColorMap().setRawData(m_streamBuffer.get(), m_streamBuffer.bytesBuffered());
- GETN(1, GIFLZWStart);
- break;
- }
-
- case GIFSubBlock: {
- const size_t bytesInBlock = this->getOneByte();
- if (bytesInBlock)
- GETN(bytesInBlock, GIFLZW);
- else {
- // Finished parsing one frame; Process next frame.
- SkASSERT(!m_frames.empty());
- // Note that some broken GIF files do not have enough LZW blocks to fully
- // decode all rows but we treat it as frame complete.
- m_frames.back()->setComplete();
- GETN(1, GIFImageStart);
- if (lastFrameToParse >= 0 && (int) m_frames.size() > lastFrameToParse) {
- m_streamBuffer.flush();
- return true;
- }
- }
- break;
- }
-
- case GIFDone: {
- m_parseCompleted = true;
- return true;
- }
-
- default:
- // We shouldn't ever get here.
- // This prevents attempting to continue reading this invalid stream.
- GETN(0, GIFDone);
- return false;
- break;
- } // switch
- m_streamBuffer.flush();
- }
-
- return true;
-}
-
-void GIFImageReader::addFrameIfNecessary()
-{
- if (m_frames.empty() || m_frames.back()->isComplete()) {
- const size_t i = m_frames.size();
- std::unique_ptr<GIFFrameContext> frame(new GIFFrameContext(i));
- if (0 == i) {
- frame->setRequiredFrame(SkCodec::kNone);
- } else {
- // FIXME: We could correct these after decoding (i.e. some frames may turn out to be
- // independent although we did not determine that here).
- const GIFFrameContext* prevFrameContext = m_frames[i - 1].get();
- switch (prevFrameContext->getDisposalMethod()) {
- case SkCodecAnimation::Keep_DisposalMethod:
- frame->setRequiredFrame(i - 1);
- break;
- case SkCodecAnimation::RestorePrevious_DisposalMethod:
- frame->setRequiredFrame(prevFrameContext->getRequiredFrame());
- break;
- case SkCodecAnimation::RestoreBGColor_DisposalMethod:
- // If the prior frame covers the whole image
- if (prevFrameContext->frameRect() == SkIRect::MakeWH(m_screenWidth,
- m_screenHeight)
- // Or the prior frame was independent
- || prevFrameContext->getRequiredFrame() == SkCodec::kNone)
- {
- // This frame is independent, since we clear everything
- // prior frame to the BG color
- frame->setRequiredFrame(SkCodec::kNone);
- } else {
- frame->setRequiredFrame(i - 1);
- }
- break;
- }
- }
- m_frames.push_back(std::move(frame));
- }
-}
-
-// FIXME: Move this method to close to doLZW().
-bool GIFLZWContext::prepareToDecode()
-{
- SkASSERT(m_frameContext->isDataSizeDefined() && m_frameContext->isHeaderDefined());
-
- // Since we use a codesize of 1 more than the datasize, we need to ensure
- // that our datasize is strictly less than the MAX_DICTIONARY_ENTRY_BITS.
- if (m_frameContext->dataSize() >= MAX_DICTIONARY_ENTRY_BITS)
- return false;
- clearCode = 1 << m_frameContext->dataSize();
- avail = clearCode + 2;
- oldcode = -1;
- codesize = m_frameContext->dataSize() + 1;
- codemask = (1 << codesize) - 1;
- datum = bits = 0;
- ipass = m_frameContext->interlaced() ? 1 : 0;
- irow = 0;
-
- // We want to know the longest sequence encodable by a dictionary with
- // MAX_DICTIONARY_ENTRIES entries. If we ignore the need to encode the base
- // values themselves at the beginning of the dictionary, as well as the need
- // for a clear code or a termination code, we could use every entry to
- // encode a series of multiple values. If the input value stream looked
- // like "AAAAA..." (a long string of just one value), the first dictionary
- // entry would encode AA, the next AAA, the next AAAA, and so forth. Thus
- // the longest sequence would be MAX_DICTIONARY_ENTRIES + 1 values.
- //
- // However, we have to account for reserved entries. The first |datasize|
- // bits are reserved for the base values, and the next two entries are
- // reserved for the clear code and termination code. In theory a GIF can
- // set the datasize to 0, meaning we have just two reserved entries, making
- // the longest sequence (MAX_DICTIONARY_ENTIRES + 1) - 2 values long. Since
- // each value is a byte, this is also the number of bytes in the longest
- // encodable sequence.
- const size_t maxBytes = MAX_DICTIONARY_ENTRIES - 1;
-
- // Now allocate the output buffer. We decode directly into this buffer
- // until we have at least one row worth of data, then call outputRow().
- // This means worst case we may have (row width - 1) bytes in the buffer
- // and then decode a sequence |maxBytes| long to append.
- rowBuffer.reset(m_frameContext->width() - 1 + maxBytes);
- rowIter = rowBuffer.begin();
- rowsRemaining = m_frameContext->height();
-
- // Clearing the whole suffix table lets us be more tolerant of bad data.
- for (int i = 0; i < clearCode; ++i) {
- suffix[i] = i;
- suffixLength[i] = 1;
- }
- return true;
-}
-

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