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926 lines
36 KiB
926 lines
36 KiB
/* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Chris Saari <saari@netscape.com>
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* Apple Computer
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*
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* Alternatively, the contents of this file may be used under the terms of
|
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
|
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* of those above. If you wish to allow use of your version of this file only
|
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* under the terms of either the GPL or the LGPL, and not to allow others to
|
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* use your version of this file under the terms of the MPL, indicate your
|
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
|
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/*
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The Graphics Interchange Format(c) is the copyright property of CompuServe
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Incorporated. Only CompuServe Incorporated is authorized to define, redefine,
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enhance, alter, modify or change in any way the definition of the format.
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CompuServe Incorporated hereby grants a limited, non-exclusive, royalty-free
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license for the use of the Graphics Interchange Format(sm) in computer
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software; computer software utilizing GIF(sm) must acknowledge ownership of the
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Graphics Interchange Format and its Service Mark by CompuServe Incorporated, in
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User and Technical Documentation. Computer software utilizing GIF, which is
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distributed or may be distributed without User or Technical Documentation must
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|
display to the screen or printer a message acknowledging ownership of the
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|
Graphics Interchange Format and the Service Mark by CompuServe Incorporated; in
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this case, the acknowledgement may be displayed in an opening screen or leading
|
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banner, or a closing screen or trailing banner. A message such as the following
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may be used:
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"The Graphics Interchange Format(c) is the Copyright property of
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CompuServe Incorporated. GIF(sm) is a Service Mark property of
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CompuServe Incorporated."
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For further information, please contact :
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CompuServe Incorporated
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Graphics Technology Department
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5000 Arlington Center Boulevard
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Columbus, Ohio 43220
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U. S. A.
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CompuServe Incorporated maintains a mailing list with all those individuals and
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organizations who wish to receive copies of this document when it is corrected
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or revised. This service is offered free of charge; please provide us with your
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mailing address.
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*/
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#include "SkGifImageReader.h"
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#include "SkColorPriv.h"
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#include "SkGifCodec.h"
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#include <algorithm>
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#include <string.h>
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|
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// GETN(n, s) requests at least 'n' bytes available from 'q', at start of state 's'.
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//
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// Note, the hold will never need to be bigger than 256 bytes to gather up in the hold,
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// as each GIF block (except colormaps) can never be bigger than 256 bytes.
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// Colormaps are directly copied in the resp. global_colormap or dynamically allocated local_colormap.
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// So a fixed buffer in SkGifImageReader is good enough.
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// This buffer is only needed to copy left-over data from one GifWrite call to the next
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#define GETN(n, s) \
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do { \
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m_bytesToConsume = (n); \
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m_state = (s); \
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} while (0)
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// Get a 16-bit value stored in little-endian format.
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#define GETINT16(p) ((p)[1]<<8|(p)[0])
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namespace {
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bool is_palette_index_valid(int transparentIndex) {
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// -1 is a signal that there is no transparent index.
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// Otherwise, it is encoded in 8 bits, and all 256 values are considered
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// valid since a GIF may use an index outside of the palette to be
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// transparent.
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return transparentIndex >= 0;
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}
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} // anonymous namespace
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// Send the data to the display front-end.
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void SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
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{
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int drowStart = irow;
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int drowEnd = irow;
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// Haeberli-inspired hack for interlaced GIFs: Replicate lines while
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// displaying to diminish the "venetian-blind" effect as the image is
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// loaded. Adjust pixel vertical positions to avoid the appearance of the
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// image crawling up the screen as successive passes are drawn.
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if (m_frameContext->progressiveDisplay() && m_frameContext->interlaced() && ipass < 4) {
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unsigned rowDup = 0;
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unsigned rowShift = 0;
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switch (ipass) {
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case 1:
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rowDup = 7;
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rowShift = 3;
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break;
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case 2:
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rowDup = 3;
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rowShift = 1;
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break;
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case 3:
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rowDup = 1;
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rowShift = 0;
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break;
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default:
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break;
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}
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drowStart -= rowShift;
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drowEnd = drowStart + rowDup;
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// Extend if bottom edge isn't covered because of the shift upward.
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if ((unsigned)((m_frameContext->height() - 1) - drowEnd) <= rowShift)
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drowEnd = m_frameContext->height() - 1;
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// Clamp first and last rows to upper and lower edge of image.
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if (drowStart < 0)
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drowStart = 0;
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if (drowEnd >= m_frameContext->height())
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drowEnd = m_frameContext->height() - 1;
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}
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// Protect against too much image data.
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if (drowStart >= m_frameContext->height())
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return;
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// CALLBACK: Let the client know we have decoded a row.
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const bool writeTransparentPixels =
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SkCodec::kNoFrame == m_frameContext->getRequiredFrame();
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m_client->haveDecodedRow(m_frameContext->frameId(), rowBegin,
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drowStart, drowEnd - drowStart + 1, writeTransparentPixels);
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if (!m_frameContext->interlaced())
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irow++;
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else {
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do {
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switch (ipass) {
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case 1:
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irow += 8;
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if (irow >= (unsigned) m_frameContext->height()) {
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ipass++;
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irow = 4;
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}
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break;
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case 2:
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irow += 8;
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if (irow >= (unsigned) m_frameContext->height()) {
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ipass++;
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irow = 2;
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}
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break;
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case 3:
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irow += 4;
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if (irow >= (unsigned) m_frameContext->height()) {
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ipass++;
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irow = 1;
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}
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break;
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case 4:
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irow += 2;
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if (irow >= (unsigned) m_frameContext->height()) {
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ipass++;
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irow = 0;
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}
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break;
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default:
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break;
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}
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} while (irow > (unsigned) (m_frameContext->height() - 1));
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}
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}
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// Perform Lempel-Ziv-Welch decoding.
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// Returns true if decoding was successful. In this case the block will have been completely consumed and/or rowsRemaining will be 0.
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// Otherwise, decoding failed; returns false in this case, which will always cause the SkGifImageReader to set the "decode failed" flag.
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bool SkGIFLZWContext::doLZW(const unsigned char* block, size_t bytesInBlock)
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{
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const int width = m_frameContext->width();
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if (rowIter == rowBuffer.end())
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return true;
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for (const unsigned char* ch = block; bytesInBlock-- > 0; ch++) {
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// Feed the next byte into the decoder's 32-bit input buffer.
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datum += ((int) *ch) << bits;
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bits += 8;
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// Check for underflow of decoder's 32-bit input buffer.
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while (bits >= codesize) {
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// Get the leading variable-length symbol from the data stream.
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int code = datum & codemask;
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datum >>= codesize;
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bits -= codesize;
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// Reset the dictionary to its original state, if requested.
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if (code == clearCode) {
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codesize = m_frameContext->dataSize() + 1;
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codemask = (1 << codesize) - 1;
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avail = clearCode + 2;
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oldcode = -1;
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continue;
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}
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// Check for explicit end-of-stream code.
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if (code == (clearCode + 1)) {
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// end-of-stream should only appear after all image data.
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if (!rowsRemaining)
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return true;
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return false;
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}
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const int tempCode = code;
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unsigned short codeLength = 0;
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if (code < avail) {
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// This is a pre-existing code, so we already know what it
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// encodes.
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codeLength = suffixLength[code];
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rowIter += codeLength;
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} else if (code == avail && oldcode != -1) {
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// This is a new code just being added to the dictionary.
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// It must encode the contents of the previous code, plus
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// the first character of the previous code again.
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codeLength = suffixLength[oldcode] + 1;
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rowIter += codeLength;
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*--rowIter = firstchar;
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code = oldcode;
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} else {
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// This is an invalid code. The dictionary is just initialized
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// and the code is incomplete. We don't know how to handle
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// this case.
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return false;
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}
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while (code >= clearCode) {
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*--rowIter = suffix[code];
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code = prefix[code];
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}
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*--rowIter = firstchar = suffix[code];
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// Define a new codeword in the dictionary as long as we've read
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// more than one value from the stream.
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if (avail < SK_MAX_DICTIONARY_ENTRIES && oldcode != -1) {
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prefix[avail] = oldcode;
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suffix[avail] = firstchar;
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suffixLength[avail] = suffixLength[oldcode] + 1;
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++avail;
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// If we've used up all the codewords of a given length
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// increase the length of codewords by one bit, but don't
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// exceed the specified maximum codeword size.
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if (!(avail & codemask) && avail < SK_MAX_DICTIONARY_ENTRIES) {
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++codesize;
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codemask += avail;
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}
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}
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oldcode = tempCode;
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rowIter += codeLength;
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// Output as many rows as possible.
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unsigned char* rowBegin = rowBuffer.begin();
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for (; rowBegin + width <= rowIter; rowBegin += width) {
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outputRow(rowBegin);
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rowsRemaining--;
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if (!rowsRemaining)
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return true;
|
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}
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|
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if (rowBegin != rowBuffer.begin()) {
|
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// Move the remaining bytes to the beginning of the buffer.
|
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const size_t bytesToCopy = rowIter - rowBegin;
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memcpy(&rowBuffer.front(), rowBegin, bytesToCopy);
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rowIter = rowBuffer.begin() + bytesToCopy;
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}
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}
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}
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return true;
|
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}
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|
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sk_sp<SkColorTable> SkGIFColorMap::buildTable(SkStreamBuffer* streamBuffer, SkColorType colorType,
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int transparentPixel) const
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{
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if (!m_isDefined)
|
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return nullptr;
|
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|
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const PackColorProc proc = choose_pack_color_proc(false, colorType);
|
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if (m_table && proc == m_packColorProc && m_transPixel == transparentPixel) {
|
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SkASSERT(transparentPixel == kNotFound || transparentPixel > m_table->count()
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|| m_table->operator[](transparentPixel) == SK_ColorTRANSPARENT);
|
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// This SkColorTable has already been built with the same transparent color and
|
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// packing proc. Reuse it.
|
|
return m_table;
|
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}
|
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m_packColorProc = proc;
|
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m_transPixel = transparentPixel;
|
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const size_t bytes = m_colors * SK_BYTES_PER_COLORMAP_ENTRY;
|
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sk_sp<SkData> rawData(streamBuffer->getDataAtPosition(m_position, bytes));
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if (!rawData) {
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return nullptr;
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}
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|
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SkASSERT(m_colors <= SK_MAX_COLORS);
|
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const uint8_t* srcColormap = rawData->bytes();
|
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SkPMColor colorStorage[SK_MAX_COLORS];
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for (int i = 0; i < m_colors; i++) {
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if (i == transparentPixel) {
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colorStorage[i] = SK_ColorTRANSPARENT;
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} else {
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colorStorage[i] = proc(255, srcColormap[0], srcColormap[1], srcColormap[2]);
|
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}
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srcColormap += SK_BYTES_PER_COLORMAP_ENTRY;
|
|
}
|
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for (int i = m_colors; i < SK_MAX_COLORS; i++) {
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colorStorage[i] = SK_ColorTRANSPARENT;
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}
|
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m_table = sk_sp<SkColorTable>(new SkColorTable(colorStorage, SK_MAX_COLORS));
|
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return m_table;
|
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}
|
|
|
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sk_sp<SkColorTable> SkGifImageReader::getColorTable(SkColorType colorType, int index) {
|
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if (index < 0 || index >= m_frames.count()) {
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return nullptr;
|
|
}
|
|
|
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const SkGIFFrameContext* frameContext = m_frames[index].get();
|
|
const SkGIFColorMap& localColorMap = frameContext->localColorMap();
|
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const int transPix = frameContext->transparentPixel();
|
|
if (localColorMap.isDefined()) {
|
|
return localColorMap.buildTable(&m_streamBuffer, colorType, transPix);
|
|
}
|
|
if (m_globalColorMap.isDefined()) {
|
|
return m_globalColorMap.buildTable(&m_streamBuffer, colorType, transPix);
|
|
}
|
|
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 SkGifImageReader 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 SkGIFFrameContext::decode(SkStreamBuffer* streamBuffer, SkGifCodec* client,
|
|
bool* frameComplete)
|
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{
|
|
*frameComplete = false;
|
|
if (!m_lzwContext) {
|
|
// Wait for more data to properly initialize SkGIFLZWContext.
|
|
if (!isDataSizeDefined() || !isHeaderDefined())
|
|
return true;
|
|
|
|
m_lzwContext.reset(new SkGIFLZWContext(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.count() && m_lzwContext->hasRemainingRows()) {
|
|
const auto& block = m_lzwBlocks[m_currentLzwBlock];
|
|
const size_t len = block.blockSize;
|
|
|
|
sk_sp<SkData> data(streamBuffer->getDataAtPosition(block.blockPosition, len));
|
|
if (!data) {
|
|
return false;
|
|
}
|
|
if (!m_lzwContext->doLZW(reinterpret_cast<const unsigned char*>(data->data()), len)) {
|
|
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 SkGIFFrameContext: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 SkGifImageReader::decode(int frameIndex, bool* frameComplete)
|
|
{
|
|
SkGIFFrameContext* currentFrame = m_frames[frameIndex].get();
|
|
|
|
return currentFrame->decode(&m_streamBuffer, m_client, frameComplete);
|
|
}
|
|
|
|
// Parse incoming GIF data stream into internal data structures.
|
|
SkCodec::Result SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
|
|
{
|
|
if (m_parseCompleted) {
|
|
return SkCodec::kSuccess;
|
|
}
|
|
|
|
if (SkGIFLoopCountQuery == query && m_loopCount != cLoopCountNotSeen) {
|
|
// Loop count has already been parsed.
|
|
return SkCodec::kSuccess;
|
|
}
|
|
|
|
// SkGIFSizeQuery and SkGIFFrameCountQuery are negative, so this is only meaningful when >= 0.
|
|
const int lastFrameToParse = (int) query;
|
|
if (lastFrameToParse >= 0 && m_frames.count() > lastFrameToParse
|
|
&& m_frames[lastFrameToParse]->isComplete()) {
|
|
// We have already parsed this frame.
|
|
return SkCodec::kSuccess;
|
|
}
|
|
|
|
while (true) {
|
|
if (!m_streamBuffer.buffer(m_bytesToConsume)) {
|
|
// The stream does not yet have enough data.
|
|
return SkCodec::kIncompleteInput;
|
|
}
|
|
|
|
switch (m_state) {
|
|
case SkGIFLZW: {
|
|
SkASSERT(!m_frames.empty());
|
|
auto* frame = m_frames.back().get();
|
|
frame->addLzwBlock(m_streamBuffer.markPosition(), m_bytesToConsume);
|
|
GETN(1, SkGIFSubBlock);
|
|
break;
|
|
}
|
|
case SkGIFLZWStart: {
|
|
SkASSERT(!m_frames.empty());
|
|
auto* currentFrame = m_frames.back().get();
|
|
|
|
currentFrame->setDataSize(this->getOneByte());
|
|
GETN(1, SkGIFSubBlock);
|
|
break;
|
|
}
|
|
|
|
case SkGIFType: {
|
|
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, SkGIFDone);
|
|
return SkCodec::kInvalidInput;
|
|
}
|
|
GETN(7, SkGIFGlobalHeader);
|
|
break;
|
|
}
|
|
|
|
case SkGIFGlobalHeader: {
|
|
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.
|
|
fScreenWidth = GETINT16(currentComponent);
|
|
fScreenHeight = GETINT16(currentComponent + 2);
|
|
|
|
const int globalColorMapColors = 2 << (currentComponent[4] & 0x07);
|
|
|
|
if ((currentComponent[4] & 0x80) && globalColorMapColors > 0) { /* global map */
|
|
m_globalColorMap.setNumColors(globalColorMapColors);
|
|
GETN(SK_BYTES_PER_COLORMAP_ENTRY * globalColorMapColors, SkGIFGlobalColormap);
|
|
break;
|
|
}
|
|
|
|
GETN(1, SkGIFImageStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFGlobalColormap: {
|
|
m_globalColorMap.setTablePosition(m_streamBuffer.markPosition());
|
|
GETN(1, SkGIFImageStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFImageStart: {
|
|
const char currentComponent = m_streamBuffer.get()[0];
|
|
|
|
if (currentComponent == '!') { // extension.
|
|
GETN(2, SkGIFExtension);
|
|
break;
|
|
}
|
|
|
|
if (currentComponent == ',') { // image separator.
|
|
GETN(9, SkGIFImageHeader);
|
|
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, SkGIFDone);
|
|
break;
|
|
}
|
|
|
|
case SkGIFExtension: {
|
|
const unsigned char* currentComponent =
|
|
reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
|
|
|
|
size_t bytesInBlock = currentComponent[1];
|
|
SkGIFState exceptionState = SkGIFSkipBlock;
|
|
|
|
switch (*currentComponent) {
|
|
case 0xf9:
|
|
// The GIF spec mandates that the GIFControlExtension header block length is 4 bytes,
|
|
exceptionState = SkGIFControlExtension;
|
|
// 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 = SkGIFApplicationExtension;
|
|
break;
|
|
|
|
case 0xfe:
|
|
exceptionState = SkGIFConsumeComment;
|
|
break;
|
|
}
|
|
|
|
if (bytesInBlock)
|
|
GETN(bytesInBlock, exceptionState);
|
|
else
|
|
GETN(1, SkGIFImageStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFConsumeBlock: {
|
|
const unsigned char currentComponent = this->getOneByte();
|
|
if (!currentComponent)
|
|
GETN(1, SkGIFImageStart);
|
|
else
|
|
GETN(currentComponent, SkGIFSkipBlock);
|
|
break;
|
|
}
|
|
|
|
case SkGIFSkipBlock: {
|
|
GETN(1, SkGIFConsumeBlock);
|
|
break;
|
|
}
|
|
|
|
case SkGIFControlExtension: {
|
|
const unsigned char* currentComponent =
|
|
reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
|
|
|
|
addFrameIfNecessary();
|
|
SkGIFFrameContext* 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::DisposalMethod::kRestorePrevious);
|
|
break;
|
|
default:
|
|
// Other values use the default.
|
|
currentFrame->setDisposalMethod(SkCodecAnimation::DisposalMethod::kKeep);
|
|
break;
|
|
}
|
|
currentFrame->setDuration(GETINT16(currentComponent + 1) * 10);
|
|
GETN(1, SkGIFConsumeBlock);
|
|
break;
|
|
}
|
|
|
|
case SkGIFCommentExtension: {
|
|
const unsigned char currentComponent = this->getOneByte();
|
|
if (currentComponent)
|
|
GETN(currentComponent, SkGIFConsumeComment);
|
|
else
|
|
GETN(1, SkGIFImageStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFConsumeComment: {
|
|
GETN(1, SkGIFCommentExtension);
|
|
break;
|
|
}
|
|
|
|
case SkGIFApplicationExtension: {
|
|
// Check for netscape application extension.
|
|
if (m_bytesToConsume == 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, SkGIFNetscapeExtensionBlock);
|
|
}
|
|
|
|
if (m_state != SkGIFNetscapeExtensionBlock)
|
|
GETN(1, SkGIFConsumeBlock);
|
|
break;
|
|
}
|
|
|
|
// Netscape-specific GIF extension: animation looping.
|
|
case SkGIFNetscapeExtensionBlock: {
|
|
const int currentComponent = this->getOneByte();
|
|
// SkGIFConsumeNetscapeExtension always reads 3 bytes from the stream; we should at least wait for this amount.
|
|
if (currentComponent)
|
|
GETN(std::max(3, currentComponent), SkGIFConsumeNetscapeExtension);
|
|
else
|
|
GETN(1, SkGIFImageStart);
|
|
break;
|
|
}
|
|
|
|
// Parse netscape-specific application extensions
|
|
case SkGIFConsumeNetscapeExtension: {
|
|
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 = SkCodec::kRepetitionCountInfinite;
|
|
|
|
GETN(1, SkGIFNetscapeExtensionBlock);
|
|
|
|
if (SkGIFLoopCountQuery == query) {
|
|
m_streamBuffer.flush();
|
|
return SkCodec::kSuccess;
|
|
}
|
|
} 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, SkGIFNetscapeExtensionBlock);
|
|
} else {
|
|
// 0,3-7 are yet to be defined netscape extension codes
|
|
// This prevents attempting to continue reading this invalid stream.
|
|
GETN(0, SkGIFDone);
|
|
return SkCodec::kInvalidInput;
|
|
}
|
|
break;
|
|
}
|
|
|
|
case SkGIFImageHeader: {
|
|
int 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()) {
|
|
fScreenHeight = std::max(fScreenHeight, yOffset + height);
|
|
fScreenWidth = std::max(fScreenWidth, 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 = fScreenHeight;
|
|
width = fScreenWidth;
|
|
if (!height || !width) {
|
|
// This prevents attempting to continue reading this invalid stream.
|
|
GETN(0, SkGIFDone);
|
|
return SkCodec::kInvalidInput;
|
|
}
|
|
}
|
|
|
|
const bool isLocalColormapDefined = SkToBool(currentComponent[8] & 0x80);
|
|
// The three low-order bits of currentComponent[8] specify the bits per pixel.
|
|
const int numColors = 2 << (currentComponent[8] & 0x7);
|
|
if (currentFrameIsFirstFrame()) {
|
|
const int transPix = m_frames.empty() ? SkGIFColorMap::kNotFound
|
|
: m_frames[0]->transparentPixel();
|
|
if (is_palette_index_valid(transPix)) {
|
|
m_firstFrameHasAlpha = true;
|
|
} else {
|
|
const bool frameIsSubset = xOffset > 0 || yOffset > 0
|
|
|| width < fScreenWidth
|
|
|| height < fScreenHeight;
|
|
m_firstFrameHasAlpha = frameIsSubset;
|
|
}
|
|
}
|
|
|
|
addFrameIfNecessary();
|
|
SkGIFFrameContext* currentFrame = m_frames.back().get();
|
|
currentFrame->setHeaderDefined();
|
|
|
|
if (query == SkGIFSizeQuery) {
|
|
// 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.
|
|
return SkCodec::kSuccess;
|
|
}
|
|
|
|
|
|
currentFrame->setXYWH(xOffset, yOffset, width, height);
|
|
currentFrame->setInterlaced(SkToBool(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(SK_BYTES_PER_COLORMAP_ENTRY * numColors, SkGIFImageColormap);
|
|
break;
|
|
}
|
|
|
|
setAlphaAndRequiredFrame(currentFrame);
|
|
GETN(1, SkGIFLZWStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFImageColormap: {
|
|
SkASSERT(!m_frames.empty());
|
|
auto* currentFrame = m_frames.back().get();
|
|
auto& cmap = currentFrame->localColorMap();
|
|
cmap.setTablePosition(m_streamBuffer.markPosition());
|
|
setAlphaAndRequiredFrame(currentFrame);
|
|
GETN(1, SkGIFLZWStart);
|
|
break;
|
|
}
|
|
|
|
case SkGIFSubBlock: {
|
|
const size_t bytesInBlock = this->getOneByte();
|
|
if (bytesInBlock)
|
|
GETN(bytesInBlock, SkGIFLZW);
|
|
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, SkGIFImageStart);
|
|
if (lastFrameToParse >= 0 && m_frames.count() > lastFrameToParse) {
|
|
m_streamBuffer.flush();
|
|
return SkCodec::kSuccess;
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
|
|
case SkGIFDone: {
|
|
m_parseCompleted = true;
|
|
return SkCodec::kSuccess;
|
|
}
|
|
|
|
default:
|
|
// We shouldn't ever get here.
|
|
// This prevents attempting to continue reading this invalid stream.
|
|
GETN(0, SkGIFDone);
|
|
return SkCodec::kInvalidInput;
|
|
break;
|
|
} // switch
|
|
m_streamBuffer.flush();
|
|
}
|
|
}
|
|
|
|
void SkGifImageReader::addFrameIfNecessary()
|
|
{
|
|
if (m_frames.empty() || m_frames.back()->isComplete()) {
|
|
const int i = m_frames.count();
|
|
m_frames.emplace_back(new SkGIFFrameContext(i));
|
|
}
|
|
}
|
|
|
|
SkEncodedInfo::Alpha SkGIFFrameContext::onReportedAlpha() const {
|
|
// Note: We could correct these after decoding - i.e. some frames may turn out to be
|
|
// independent and opaque if they do not use the transparent pixel, but that would require
|
|
// checking whether each pixel used the transparent index.
|
|
return is_palette_index_valid(this->transparentPixel()) ? SkEncodedInfo::kBinary_Alpha
|
|
: SkEncodedInfo::kOpaque_Alpha;
|
|
}
|
|
|
|
// FIXME: Move this method to close to doLZW().
|
|
bool SkGIFLZWContext::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 SK_MAX_DICTIONARY_ENTRY_BITS.
|
|
if (m_frameContext->dataSize() >= SK_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
|
|
// SK_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 SK_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 (SK_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 = SK_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;
|
|
}
|
|
|