skia2/third_party/gif/SkGifImageReader.h
Matt Sarett 4ef986db65 Write transparent pixels more often in SkGifImageReader
This stems from a behavior difference between Skia and Chrome.
In Skia, we want to write transparent pixels as often as possible.
(It's faster than checking if we should skip each pixel.)
In Chrome, they avoid writing transparent pixels unless
absolutely necessary.

We were cautious about changing behavior when this first landed,
but this is easier to think about in a smaller change (right now).
(1) We can always write transparent pixels when we are writing
    an independent frame.
(2) There is no need for the progressiveDisplay() check.  We
    only ever use progressive display methods on the first
    frame - and the first frame is always independent.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4379

Change-Id: I82048a08e2003aac216f483c7db8df997b687149
Reviewed-on: https://skia-review.googlesource.com/4379
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
2016-11-03 19:25:39 +00:00

408 lines
14 KiB
C++

/* -*- Mode: C; tab-width: 4; 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 Communicator client 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):
*
* 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 ***** */
#ifndef SkGifImageReader_h
#define SkGifImageReader_h
// Define ourselves as the clientPtr. Mozilla just hacked their C++ callback class into this old C decoder,
// so we will too.
class SkGifCodec;
#include "SkCodec.h"
#include "SkCodecPriv.h"
#include "SkCodecAnimation.h"
#include "SkColorTable.h"
#include "SkData.h"
#include "SkImageInfo.h"
#include "SkStreamBuffer.h"
#include "../private/SkTArray.h"
#include <memory>
#include <vector>
typedef SkTArray<unsigned char, true> SkGIFRow;
#define SK_MAX_DICTIONARY_ENTRY_BITS 12
#define SK_MAX_DICTIONARY_ENTRIES 4096 // 2^SK_MAX_DICTIONARY_ENTRY_BITS
#define SK_MAX_COLORS 256
#define SK_BYTES_PER_COLORMAP_ENTRY 3
// List of possible parsing states.
enum SkGIFState {
SkGIFType,
SkGIFGlobalHeader,
SkGIFGlobalColormap,
SkGIFImageStart,
SkGIFImageHeader,
SkGIFImageColormap,
SkGIFImageBody,
SkGIFLZWStart,
SkGIFLZW,
SkGIFSubBlock,
SkGIFExtension,
SkGIFControlExtension,
SkGIFConsumeBlock,
SkGIFSkipBlock,
SkGIFDone,
SkGIFCommentExtension,
SkGIFApplicationExtension,
SkGIFNetscapeExtensionBlock,
SkGIFConsumeNetscapeExtension,
SkGIFConsumeComment
};
struct SkGIFFrameContext;
class SkGIFColorMap;
// LZW decoder state machine.
class SkGIFLZWContext final : public SkNoncopyable {
public:
SkGIFLZWContext(SkGifCodec* client, const SkGIFFrameContext* frameContext)
: codesize(0)
, codemask(0)
, clearCode(0)
, avail(0)
, oldcode(0)
, firstchar(0)
, bits(0)
, datum(0)
, ipass(0)
, irow(0)
, rowsRemaining(0)
, rowIter(0)
, m_client(client)
, m_frameContext(frameContext)
{ }
bool prepareToDecode(const SkGIFColorMap& globalMap);
bool outputRow(const unsigned char* rowBegin);
bool doLZW(const unsigned char* block, size_t bytesInBlock);
bool hasRemainingRows() { return SkToBool(rowsRemaining); }
private:
// LZW decoding states and output states.
int codesize;
int codemask;
int clearCode; // Codeword used to trigger dictionary reset.
int avail; // Index of next available slot in dictionary.
int oldcode;
unsigned char firstchar;
int bits; // Number of unread bits in "datum".
int datum; // 32-bit input buffer.
int ipass; // Interlace pass; Ranges 1-4 if interlaced.
size_t irow; // Current output row, starting at zero.
size_t rowsRemaining; // Rows remaining to be output.
unsigned short prefix[SK_MAX_DICTIONARY_ENTRIES];
unsigned char suffix[SK_MAX_DICTIONARY_ENTRIES];
unsigned short suffixLength[SK_MAX_DICTIONARY_ENTRIES];
SkGIFRow rowBuffer; // Single scanline temporary buffer.
unsigned char* rowIter;
SkGifCodec* const m_client;
const SkGIFFrameContext* m_frameContext;
};
class SkGIFColorMap final {
public:
SkGIFColorMap()
: m_isDefined(false)
, m_colors(0)
, m_packColorProc(nullptr)
{
}
void setNumColors(size_t colors) {
m_colors = colors;
}
size_t numColors() const { return m_colors; }
void setRawData(const char* data, size_t size)
{
// FIXME: Can we avoid this copy?
m_rawData = SkData::MakeWithCopy(data, size);
SkASSERT(m_colors * SK_BYTES_PER_COLORMAP_ENTRY == size);
m_isDefined = true;
}
bool isDefined() const { return m_isDefined; }
// Build RGBA table using the data stream.
sk_sp<SkColorTable> buildTable(SkColorType dstColorType, size_t transparentPixel) const;
private:
bool m_isDefined;
size_t m_colors;
sk_sp<SkData> m_rawData;
mutable PackColorProc m_packColorProc;
mutable sk_sp<SkColorTable> m_table;
};
// LocalFrame output state machine.
struct SkGIFFrameContext : SkNoncopyable {
public:
SkGIFFrameContext(int id)
: m_frameId(id)
, m_xOffset(0)
, m_yOffset(0)
, m_width(0)
, m_height(0)
, m_transparentPixel(kNotFound)
, m_disposalMethod(SkCodecAnimation::Keep_DisposalMethod)
, m_requiredFrame(SkCodec::kNone)
, m_dataSize(0)
, m_progressiveDisplay(false)
, m_interlaced(false)
, m_delayTime(0)
, m_currentLzwBlock(0)
, m_isComplete(false)
, m_isHeaderDefined(false)
, m_isDataSizeDefined(false)
{
}
static constexpr size_t kNotFound = static_cast<size_t>(-1);
~SkGIFFrameContext()
{
}
void addLzwBlock(const void* data, size_t size)
{
m_lzwBlocks.push_back(SkData::MakeWithCopy(data, size));
}
bool decode(SkGifCodec* client, const SkGIFColorMap& globalMap, bool* frameDecoded);
int frameId() const { return m_frameId; }
void setRect(unsigned x, unsigned y, unsigned width, unsigned height)
{
m_xOffset = x;
m_yOffset = y;
m_width = width;
m_height = height;
}
SkIRect frameRect() const { return SkIRect::MakeXYWH(m_xOffset, m_yOffset, m_width, m_height); }
unsigned xOffset() const { return m_xOffset; }
unsigned yOffset() const { return m_yOffset; }
unsigned width() const { return m_width; }
unsigned height() const { return m_height; }
size_t transparentPixel() const { return m_transparentPixel; }
void setTransparentPixel(size_t pixel) { m_transparentPixel = pixel; }
SkCodecAnimation::DisposalMethod getDisposalMethod() const { return m_disposalMethod; }
void setDisposalMethod(SkCodecAnimation::DisposalMethod disposalMethod) { m_disposalMethod = disposalMethod; }
size_t getRequiredFrame() const { return m_requiredFrame; }
void setRequiredFrame(size_t req) { m_requiredFrame = req; }
unsigned delayTime() const { return m_delayTime; }
void setDelayTime(unsigned delay) { m_delayTime = delay; }
bool isComplete() const { return m_isComplete; }
void setComplete() { m_isComplete = true; }
bool isHeaderDefined() const { return m_isHeaderDefined; }
void setHeaderDefined() { m_isHeaderDefined = true; }
bool isDataSizeDefined() const { return m_isDataSizeDefined; }
int dataSize() const { return m_dataSize; }
void setDataSize(int size)
{
m_dataSize = size;
m_isDataSizeDefined = true;
}
bool progressiveDisplay() const { return m_progressiveDisplay; }
void setProgressiveDisplay(bool progressiveDisplay) { m_progressiveDisplay = progressiveDisplay; }
bool interlaced() const { return m_interlaced; }
void setInterlaced(bool interlaced) { m_interlaced = interlaced; }
void clearDecodeState() { m_lzwContext.reset(); }
const SkGIFColorMap& localColorMap() const { return m_localColorMap; }
SkGIFColorMap& localColorMap() { return m_localColorMap; }
private:
int m_frameId;
unsigned m_xOffset;
unsigned m_yOffset; // With respect to "screen" origin.
unsigned m_width;
unsigned m_height;
size_t m_transparentPixel; // Index of transparent pixel. Value is kNotFound if there is no transparent pixel.
SkCodecAnimation::DisposalMethod m_disposalMethod; // Restore to background, leave in place, etc.
size_t m_requiredFrame;
int m_dataSize;
bool m_progressiveDisplay; // If true, do Haeberli interlace hack.
bool m_interlaced; // True, if scanlines arrive interlaced order.
unsigned m_delayTime; // Display time, in milliseconds, for this image in a multi-image GIF.
std::unique_ptr<SkGIFLZWContext> m_lzwContext;
std::vector<sk_sp<SkData>> m_lzwBlocks; // LZW blocks for this frame.
SkGIFColorMap m_localColorMap;
size_t m_currentLzwBlock;
bool m_isComplete;
bool m_isHeaderDefined;
bool m_isDataSizeDefined;
};
class SkGifImageReader final : public SkNoncopyable {
public:
// This takes ownership of stream.
SkGifImageReader(SkStream* stream)
: m_client(nullptr)
, m_state(SkGIFType)
, m_bytesToConsume(6) // Number of bytes for GIF type, either "GIF87a" or "GIF89a".
, m_version(0)
, m_screenWidth(0)
, m_screenHeight(0)
, m_loopCount(cLoopCountNotSeen)
, m_streamBuffer(stream)
, m_parseCompleted(false)
, m_firstFrameHasAlpha(false)
, m_firstFrameSupportsIndex8(false)
{
}
~SkGifImageReader()
{
}
void setClient(SkGifCodec* client) { m_client = client; }
unsigned screenWidth() const { return m_screenWidth; }
unsigned screenHeight() const { return m_screenHeight; }
// Option to pass to parse(). All enums are negative, because a non-negative value is used to
// indicate that the Reader should parse up to and including the frame indicated.
enum SkGIFParseQuery {
// Parse enough to determine the size. Note that this parses the first frame's header,
// since we may decide to expand based on the frame's dimensions.
SkGIFSizeQuery = -1,
// Parse to the end, so we know about all frames.
SkGIFFrameCountQuery = -2,
// Parse until we see the loop count.
SkGIFLoopCountQuery = -3,
};
// Parse incoming GIF data stream into internal data structures.
// Non-negative values are used to indicate to parse through that frame.
// Return true if parsing has progressed or there is not enough data.
// Return false if a fatal error is encountered.
bool parse(SkGIFParseQuery);
// Decode the frame indicated by frameIndex.
// frameComplete will be set to true if the frame is completely decoded.
// The method returns false if there is an error.
bool decode(size_t frameIndex, bool* frameComplete);
size_t imagesCount() const
{
if (m_frames.empty())
return 0;
// This avoids counting an empty frame when the file is truncated right after
// SkGIFControlExtension but before SkGIFImageHeader.
// FIXME: This extra complexity is not necessary and we should just report m_frames.size().
return m_frames.back()->isHeaderDefined() ? m_frames.size() : m_frames.size() - 1;
}
int loopCount() const {
if (cLoopCountNotSeen == m_loopCount) {
return 0;
}
return m_loopCount;
}
const SkGIFColorMap& globalColorMap() const
{
return m_globalColorMap;
}
const SkGIFFrameContext* frameContext(size_t index) const
{
return index < m_frames.size() ? m_frames[index].get() : 0;
}
void clearDecodeState() {
for (size_t index = 0; index < m_frames.size(); index++) {
m_frames[index]->clearDecodeState();
}
}
// Return the color table for frame index (which may be the global color table).
sk_sp<SkColorTable> getColorTable(SkColorType dstColorType, size_t index) const;
bool firstFrameHasAlpha() const { return m_firstFrameHasAlpha; }
bool firstFrameSupportsIndex8() const { return m_firstFrameSupportsIndex8; }
private:
// Requires that one byte has been buffered into m_streamBuffer.
unsigned char getOneByte() const {
return reinterpret_cast<const unsigned char*>(m_streamBuffer.get())[0];
}
void addFrameIfNecessary();
bool currentFrameIsFirstFrame() const
{
return m_frames.empty() || (m_frames.size() == 1u && !m_frames[0]->isComplete());
}
// Unowned pointer
SkGifCodec* m_client;
// Parsing state machine.
SkGIFState m_state; // Current decoder master state.
size_t m_bytesToConsume; // Number of bytes to consume for next stage of parsing.
// Global (multi-image) state.
int m_version; // Either 89 for GIF89 or 87 for GIF87.
unsigned m_screenWidth; // Logical screen width & height.
unsigned m_screenHeight;
SkGIFColorMap m_globalColorMap;
static constexpr int cLoopCountNotSeen = -2;
int m_loopCount; // Netscape specific extension block to control the number of animation loops a GIF renders.
std::vector<std::unique_ptr<SkGIFFrameContext>> m_frames;
SkStreamBuffer m_streamBuffer;
bool m_parseCompleted;
// These values can be computed before we create a SkGIFFrameContext, so we
// store them here instead of on m_frames[0].
bool m_firstFrameHasAlpha;
bool m_firstFrameSupportsIndex8;
};
#endif