src/images/SkImageDecoder.cpp - platform/external/skqp - Gitiles

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */


 #include "SkImageDecoder.h"
 #include "SkBitmap.h"
 #include "SkImagePriv.h"
 #include "SkPixelRef.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
 #include "SkCanvas.h"

 SK_DEFINE_INST_COUNT(SkImageDecoder::Peeker)
 SK_DEFINE_INST_COUNT(SkImageDecoder::Chooser)
 SK_DEFINE_INST_COUNT(SkImageDecoderFactory)

 static SkBitmap::Config gDeviceConfig = SkBitmap::kNo_Config;

 SkBitmap::Config SkImageDecoder::GetDeviceConfig()
 {
     return gDeviceConfig;
 }

 void SkImageDecoder::SetDeviceConfig(SkBitmap::Config config)
 {
     gDeviceConfig = config;
 }

 ///////////////////////////////////////////////////////////////////////////////

 SkImageDecoder::SkImageDecoder()
     : fPeeker(NULL)
     , fChooser(NULL)
     , fAllocator(NULL)
     , fSampleSize(1)
     , fDefaultPref(SkBitmap::kNo_Config)
     , fDitherImage(true)
     , fUsePrefTable(false)
     , fPreferQualityOverSpeed(false) {
 }

 SkImageDecoder::~SkImageDecoder() {
     SkSafeUnref(fPeeker);
     SkSafeUnref(fChooser);
     SkSafeUnref(fAllocator);
 }

 SkImageDecoder::Format SkImageDecoder::getFormat() const {
     return kUnknown_Format;
 }

 const char* SkImageDecoder::getFormatName() const {
     return GetFormatName(this->getFormat());
 }

 const char* SkImageDecoder::GetFormatName(Format format) {
     switch (format) {
         case kUnknown_Format:
             return "Unknown Format";
         case kBMP_Format:
             return "BMP";
         case kGIF_Format:
             return "GIF";
         case kICO_Format:
             return "ICO";
         case kJPEG_Format:
             return "JPEG";
         case kPNG_Format:
             return "PNG";
         case kWBMP_Format:
             return "WBMP";
         case kWEBP_Format:
             return "WEBP";
         default:
             SkASSERT(!"Invalid format type!");
     }
     return "Unknown Format";
 }

 SkImageDecoder::Peeker* SkImageDecoder::setPeeker(Peeker* peeker) {
     SkRefCnt_SafeAssign(fPeeker, peeker);
     return peeker;
 }

 SkImageDecoder::Chooser* SkImageDecoder::setChooser(Chooser* chooser) {
     SkRefCnt_SafeAssign(fChooser, chooser);
     return chooser;
 }

 SkBitmap::Allocator* SkImageDecoder::setAllocator(SkBitmap::Allocator* alloc) {
     SkRefCnt_SafeAssign(fAllocator, alloc);
     return alloc;
 }

 void SkImageDecoder::setSampleSize(int size) {
     if (size < 1) {
         size = 1;
     }
     fSampleSize = size;
 }

 bool SkImageDecoder::chooseFromOneChoice(SkBitmap::Config config, int width,
                                          int height) const {
     Chooser* chooser = fChooser;

     if (NULL == chooser) {    // no chooser, we just say YES to decoding :)
         return true;
     }
     chooser->begin(1);
     chooser->inspect(0, config, width, height);
     return chooser->choose() == 0;
 }

 bool SkImageDecoder::allocPixelRef(SkBitmap* bitmap,
                                    SkColorTable* ctable) const {
     return bitmap->allocPixels(fAllocator, ctable);
 }

 ///////////////////////////////////////////////////////////////////////////////

 void SkImageDecoder::setPrefConfigTable(const SkBitmap::Config pref[6]) {
     if (NULL == pref) {
         fUsePrefTable = false;
     } else {
         fUsePrefTable = true;
         memcpy(fPrefTable, pref, sizeof(fPrefTable));
     }
 }

 SkBitmap::Config SkImageDecoder::getPrefConfig(SrcDepth srcDepth,
                                                bool srcHasAlpha) const {
     SkBitmap::Config config;

     if (fUsePrefTable) {
         int index = 0;
         switch (srcDepth) {
             case kIndex_SrcDepth:
                 index = 0;
                 break;
             case k16Bit_SrcDepth:
                 index = 2;
                 break;
             case k32Bit_SrcDepth:
                 index = 4;
                 break;
         }
         if (srcHasAlpha) {
             index += 1;
         }
         config = fPrefTable[index];
     } else {
         config = fDefaultPref;
     }

     if (SkBitmap::kNo_Config == config) {
         config = SkImageDecoder::GetDeviceConfig();
     }
     return config;
 }

 bool SkImageDecoder::decode(SkStream* stream, SkBitmap* bm,
                             SkBitmap::Config pref, Mode mode, bool reuseBitmap) {
     // we reset this to false before calling onDecode
     fShouldCancelDecode = false;
     // assign this, for use by getPrefConfig(), in case fUsePrefTable is false
     fDefaultPref = pref;

     if (reuseBitmap) {
         SkAutoLockPixels alp(*bm);
         if (NULL != bm->getPixels()) {
             return this->onDecode(stream, bm, mode);
         }
     }

     // pass a temporary bitmap, so that if we return false, we are assured of
     // leaving the caller's bitmap untouched.
     SkBitmap    tmp;
     if (!this->onDecode(stream, &tmp, mode)) {
         return false;
     }
     bm->swap(tmp);
     return true;
 }

 bool SkImageDecoder::decodeSubset(SkBitmap* bm, const SkIRect& rect,
                                   SkBitmap::Config pref) {
     // we reset this to false before calling onDecodeSubset
     fShouldCancelDecode = false;
     // assign this, for use by getPrefConfig(), in case fUsePrefTable is false
     fDefaultPref = pref;

     return this->onDecodeSubset(bm, rect);
 }

 bool SkImageDecoder::buildTileIndex(SkStream* stream,
                                 int *width, int *height) {
     // we reset this to false before calling onBuildTileIndex
     fShouldCancelDecode = false;

     return this->onBuildTileIndex(stream, width, height);
 }

 bool SkImageDecoder::cropBitmap(SkBitmap *dst, SkBitmap *src, int sampleSize,
                                 int dstX, int dstY, int width, int height,
                                 int srcX, int srcY) {
     int w = width / sampleSize;
     int h = height / sampleSize;
     if (src->getConfig() == SkBitmap::kIndex8_Config) {
         // kIndex8 does not allow drawing via an SkCanvas, as is done below.
         // Instead, use extractSubset. Note that this shares the SkPixelRef and
         // SkColorTable.
         // FIXME: Since src is discarded in practice, this holds on to more
         // pixels than is strictly necessary. Switch to a copy if memory
         // savings are more important than speed here. This also means
         // that the pixels in dst can not be reused (though there is no
         // allocation, which was already done on src).
         int x = (dstX - srcX) / sampleSize;
         int y = (dstY - srcY) / sampleSize;
         SkIRect subset = SkIRect::MakeXYWH(x, y, w, h);
         return src->extractSubset(dst, subset);
     }
     // if the destination has no pixels then we must allocate them.
     if (dst->isNull()) {
         dst->setConfig(src->getConfig(), w, h);
         dst->setIsOpaque(src->isOpaque());

         if (!this->allocPixelRef(dst, NULL)) {
             SkDEBUGF(("failed to allocate pixels needed to crop the bitmap"));
             return false;
         }
     }
     // check to see if the destination is large enough to decode the desired
     // region. If this assert fails we will just draw as much of the source
     // into the destination that we can.
     if (dst->width() < w || dst->height() < h) {
         SkDEBUGF(("SkImageDecoder::cropBitmap does not have a large enough bitmap.\n"));
     }

     // Set the Src_Mode for the paint to prevent transparency issue in the
     // dest in the event that the dest was being re-used.
     SkPaint paint;
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);

     SkCanvas canvas(*dst);
     canvas.drawSprite(*src, (srcX - dstX) / sampleSize,
                             (srcY - dstY) / sampleSize,
                             &paint);
     return true;
 }

 ///////////////////////////////////////////////////////////////////////////////

 bool SkImageDecoder::DecodeFile(const char file[], SkBitmap* bm,
                             SkBitmap::Config pref,  Mode mode, Format* format) {
     SkASSERT(file);
     SkASSERT(bm);

     SkAutoTUnref<SkStream> stream(SkStream::NewFromFile(file));
     if (stream.get()) {
         if (SkImageDecoder::DecodeStream(stream, bm, pref, mode, format)) {
             bm->pixelRef()->setURI(file);
             return true;
         }
     }
     return false;
 }

 bool SkImageDecoder::DecodeMemory(const void* buffer, size_t size, SkBitmap* bm,
                           SkBitmap::Config pref, Mode mode, Format* format) {
     if (0 == size) {
         return false;
     }
     SkASSERT(buffer);

     SkMemoryStream  stream(buffer, size);
     return SkImageDecoder::DecodeStream(&stream, bm, pref, mode, format);
 }

 /**
  *  Special allocator used by DecodeMemoryToTarget. Uses preallocated memory
  *  provided if the bm is 8888. Otherwise, uses a heap allocator. The same
  *  allocator will be used again for a copy to 8888, when the preallocated
  *  memory will be used.
  */
 class TargetAllocator : public SkBitmap::HeapAllocator {

 public:
     TargetAllocator(void* target)
         : fTarget(target) {}

     virtual bool allocPixelRef(SkBitmap* bm, SkColorTable* ct) SK_OVERRIDE {
         // If the config is not 8888, allocate a pixelref using the heap.
         // fTarget will be used to store the final pixels when copied to
         // 8888.
         if (bm->config() != SkBitmap::kARGB_8888_Config) {
             return INHERITED::allocPixelRef(bm, ct);
         }
         // In kARGB_8888_Config, there is no colortable.
         SkASSERT(NULL == ct);
         bm->setPixels(fTarget);
         return true;
     }

 private:
     void* fTarget;
     typedef SkBitmap::HeapAllocator INHERITED;
 };

 /**
  *  Helper function for DecodeMemoryToTarget. DecodeMemoryToTarget wants
  *  8888, so set the config to it. All parameters must not be null.
  *  @param decoder Decoder appropriate for this stream.
  *  @param stream Rewound stream to the encoded data.
  *  @param bitmap On success, will have its bounds set to the bounds of the
  *      encoded data, and its config set to 8888.
  *  @return True if the bounds were decoded and the bitmap is 8888 or can be
  *      copied to 8888.
  */
 static bool decode_bounds_to_8888(SkImageDecoder* decoder, SkStream* stream,
                                   SkBitmap* bitmap) {
     SkASSERT(decoder != NULL);
     SkASSERT(stream != NULL);
     SkASSERT(bitmap != NULL);

     if (!decoder->decode(stream, bitmap, SkImageDecoder::kDecodeBounds_Mode)) {
         return false;
     }

     if (bitmap->config() == SkBitmap::kARGB_8888_Config) {
         return true;
     }

     if (!bitmap->canCopyTo(SkBitmap::kARGB_8888_Config)) {
         return false;
     }

     bitmap->setConfig(SkBitmap::kARGB_8888_Config, bitmap->width(), bitmap->height());
     return true;
 }

 /**
  *  Helper function for DecodeMemoryToTarget. Decodes the stream into bitmap, and if
  *  the bitmap is not 8888, then it is copied to 8888. Either way, the end result has
  *  its pixels stored in target. All parameters must not be null.
  *  @param decoder Decoder appropriate for this stream.
  *  @param stream Rewound stream to the encoded data.
  *  @param bitmap On success, will contain the decoded image, with its pixels stored
  *      at target.
  *  @param target Preallocated memory for storing pixels.
  *  @return bool Whether the decode (and copy, if necessary) succeeded.
  */
 static bool decode_pixels_to_8888(SkImageDecoder* decoder, SkStream* stream,
                                   SkBitmap* bitmap, void* target) {
     SkASSERT(decoder != NULL);
     SkASSERT(stream != NULL);
     SkASSERT(bitmap != NULL);
     SkASSERT(target != NULL);

     TargetAllocator allocator(target);
     decoder->setAllocator(&allocator);

     bool success = decoder->decode(stream, bitmap, SkImageDecoder::kDecodePixels_Mode);
     decoder->setAllocator(NULL);

     if (!success) {
         return false;
     }

     if (bitmap->config() == SkBitmap::kARGB_8888_Config) {
         return true;
     }

     SkBitmap bm8888;
     if (!bitmap->copyTo(&bm8888, SkBitmap::kARGB_8888_Config, &allocator)) {
         return false;
     }

     bitmap->swap(bm8888);
     return true;
 }

 bool SkImageDecoder::DecodeMemoryToTarget(const void* buffer, size_t size,
                                           SkImage::Info* info,
                                           const SkBitmapFactory::Target* target) {
     if (NULL == info) {
         return false;
     }

     // FIXME: Just to get this working, implement in terms of existing
     // ImageDecoder calls.
     SkBitmap bm;
     SkMemoryStream stream(buffer, size);
     SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(&stream));
     if (NULL == decoder.get()) {
         return false;
     }

     if (!decode_bounds_to_8888(decoder.get(), &stream, &bm)) {
         return false;
     }

     SkASSERT(bm.config() == SkBitmap::kARGB_8888_Config);

     // Now set info properly.
     // Since Config is SkBitmap::kARGB_8888_Config, SkBitmapToImageInfo
     // will always succeed.
     SkAssertResult(SkBitmapToImageInfo(bm, info));

     if (NULL == target) {
         return true;
     }

     if (target->fRowBytes != SkToU32(bm.rowBytes())) {
         if (target->fRowBytes < SkImageMinRowBytes(*info)) {
             SkASSERT(!"Desired row bytes is too small");
             return false;
         }
         bm.setConfig(bm.config(), bm.width(), bm.height(), target->fRowBytes);
     }

     // SkMemoryStream.rewind() will always return true.
     SkAssertResult(stream.rewind());
     return decode_pixels_to_8888(decoder.get(), &stream, &bm, target->fAddr);
 }


 bool SkImageDecoder::DecodeStream(SkStream* stream, SkBitmap* bm,
                           SkBitmap::Config pref, Mode mode, Format* format) {
     SkASSERT(stream);
     SkASSERT(bm);

     bool success = false;
     SkImageDecoder* codec = SkImageDecoder::Factory(stream);

     if (NULL != codec) {
         success = codec->decode(stream, bm, pref, mode);
         if (success && format) {
             *format = codec->getFormat();
             if (kUnknown_Format == *format) {
                 if (stream->rewind()) {
                     *format = GetStreamFormat(stream);
                 }
             }
         }
         delete codec;
     }
     return success;
 }

 /**
  *  This function leaks, but that is okay because it is not intended
  *  to be called. It is only here so that the linker will include the
  *  decoders.
  *  Make sure to keep it in sync with images.gyp, so only the encoders
  *  which are created on a platform are linked.
  */
 void force_linking();
 void force_linking() {
     SkASSERT(false);
     CreateJPEGImageDecoder();
     CreateWEBPImageDecoder();
     CreateBMPImageDecoder();
     CreateICOImageDecoder();
     CreateWBMPImageDecoder();
     // Only link GIF and PNG on platforms that build them. See images.gyp
 #if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
     CreateGIFImageDecoder();
 #endif
 #if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
     CreatePNGImageDecoder();
 #endif
 }
	/*
	* Copyright 2006 The Android Open Source Project
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/


	#include "SkImageDecoder.h"
	#include "SkBitmap.h"
	#include "SkImagePriv.h"
	#include "SkPixelRef.h"
	#include "SkStream.h"
	#include "SkTemplates.h"
	#include "SkCanvas.h"

	SK_DEFINE_INST_COUNT(SkImageDecoder::Peeker)
	SK_DEFINE_INST_COUNT(SkImageDecoder::Chooser)
	SK_DEFINE_INST_COUNT(SkImageDecoderFactory)

	static SkBitmap::Config gDeviceConfig = SkBitmap::kNo_Config;

	SkBitmap::Config SkImageDecoder::GetDeviceConfig()
	{
	return gDeviceConfig;
	}

	void SkImageDecoder::SetDeviceConfig(SkBitmap::Config config)
	{
	gDeviceConfig = config;
	}

	///////////////////////////////////////////////////////////////////////////////

	SkImageDecoder::SkImageDecoder()
	: fPeeker(NULL)
	, fChooser(NULL)
	, fAllocator(NULL)
	, fSampleSize(1)
	, fDefaultPref(SkBitmap::kNo_Config)
	, fDitherImage(true)
	, fUsePrefTable(false)
	, fPreferQualityOverSpeed(false) {
	}

	SkImageDecoder::~SkImageDecoder() {
	SkSafeUnref(fPeeker);
	SkSafeUnref(fChooser);
	SkSafeUnref(fAllocator);
	}

	SkImageDecoder::Format SkImageDecoder::getFormat() const {
	return kUnknown_Format;
	}

	const char* SkImageDecoder::getFormatName() const {
	return GetFormatName(this->getFormat());
	}

	const char* SkImageDecoder::GetFormatName(Format format) {
	switch (format) {
	case kUnknown_Format:
	return "Unknown Format";
	case kBMP_Format:
	return "BMP";
	case kGIF_Format:
	return "GIF";
	case kICO_Format:
	return "ICO";
	case kJPEG_Format:
	return "JPEG";
	case kPNG_Format:
	return "PNG";
	case kWBMP_Format:
	return "WBMP";
	case kWEBP_Format:
	return "WEBP";
	default:
	SkASSERT(!"Invalid format type!");
	}
	return "Unknown Format";
	}

	SkImageDecoder::Peeker* SkImageDecoder::setPeeker(Peeker* peeker) {
	SkRefCnt_SafeAssign(fPeeker, peeker);
	return peeker;
	}

	SkImageDecoder::Chooser* SkImageDecoder::setChooser(Chooser* chooser) {
	SkRefCnt_SafeAssign(fChooser, chooser);
	return chooser;
	}

	SkBitmap::Allocator* SkImageDecoder::setAllocator(SkBitmap::Allocator* alloc) {
	SkRefCnt_SafeAssign(fAllocator, alloc);
	return alloc;
	}

	void SkImageDecoder::setSampleSize(int size) {
	if (size < 1) {
	size = 1;
	}
	fSampleSize = size;
	}

	bool SkImageDecoder::chooseFromOneChoice(SkBitmap::Config config, int width,
	int height) const {
	Chooser* chooser = fChooser;

	if (NULL == chooser) { // no chooser, we just say YES to decoding :)
	return true;
	}
	chooser->begin(1);
	chooser->inspect(0, config, width, height);
	return chooser->choose() == 0;
	}

	bool SkImageDecoder::allocPixelRef(SkBitmap* bitmap,
	SkColorTable* ctable) const {
	return bitmap->allocPixels(fAllocator, ctable);
	}

	///////////////////////////////////////////////////////////////////////////////

	void SkImageDecoder::setPrefConfigTable(const SkBitmap::Config pref[6]) {
	if (NULL == pref) {
	fUsePrefTable = false;
	} else {
	fUsePrefTable = true;
	memcpy(fPrefTable, pref, sizeof(fPrefTable));
	}
	}

	SkBitmap::Config SkImageDecoder::getPrefConfig(SrcDepth srcDepth,
	bool srcHasAlpha) const {
	SkBitmap::Config config;

	if (fUsePrefTable) {
	int index = 0;
	switch (srcDepth) {
	case kIndex_SrcDepth:
	index = 0;
	break;
	case k16Bit_SrcDepth:
	index = 2;
	break;
	case k32Bit_SrcDepth:
	index = 4;
	break;
	}
	if (srcHasAlpha) {
	index += 1;
	}
	config = fPrefTable[index];
	} else {
	config = fDefaultPref;
	}

	if (SkBitmap::kNo_Config == config) {
	config = SkImageDecoder::GetDeviceConfig();
	}
	return config;
	}

	bool SkImageDecoder::decode(SkStream* stream, SkBitmap* bm,
	SkBitmap::Config pref, Mode mode, bool reuseBitmap) {
	// we reset this to false before calling onDecode
	fShouldCancelDecode = false;
	// assign this, for use by getPrefConfig(), in case fUsePrefTable is false
	fDefaultPref = pref;

	if (reuseBitmap) {
	SkAutoLockPixels alp(*bm);
	if (NULL != bm->getPixels()) {
	return this->onDecode(stream, bm, mode);
	}
	}

	// pass a temporary bitmap, so that if we return false, we are assured of
	// leaving the caller's bitmap untouched.
	SkBitmap tmp;
	if (!this->onDecode(stream, &tmp, mode)) {
	return false;
	}
	bm->swap(tmp);
	return true;
	}

	bool SkImageDecoder::decodeSubset(SkBitmap* bm, const SkIRect& rect,
	SkBitmap::Config pref) {
	// we reset this to false before calling onDecodeSubset
	fShouldCancelDecode = false;
	// assign this, for use by getPrefConfig(), in case fUsePrefTable is false
	fDefaultPref = pref;

	return this->onDecodeSubset(bm, rect);
	}

	bool SkImageDecoder::buildTileIndex(SkStream* stream,
	int width, int height) {
	// we reset this to false before calling onBuildTileIndex
	fShouldCancelDecode = false;

	return this->onBuildTileIndex(stream, width, height);
	}

	bool SkImageDecoder::cropBitmap(SkBitmap dst, SkBitmap src, int sampleSize,
	int dstX, int dstY, int width, int height,
	int srcX, int srcY) {
	int w = width / sampleSize;
	int h = height / sampleSize;
	if (src->getConfig() == SkBitmap::kIndex8_Config) {
	// kIndex8 does not allow drawing via an SkCanvas, as is done below.
	// Instead, use extractSubset. Note that this shares the SkPixelRef and
	// SkColorTable.
	// FIXME: Since src is discarded in practice, this holds on to more
	// pixels than is strictly necessary. Switch to a copy if memory
	// savings are more important than speed here. This also means
	// that the pixels in dst can not be reused (though there is no
	// allocation, which was already done on src).
	int x = (dstX - srcX) / sampleSize;
	int y = (dstY - srcY) / sampleSize;
	SkIRect subset = SkIRect::MakeXYWH(x, y, w, h);
	return src->extractSubset(dst, subset);
	}
	// if the destination has no pixels then we must allocate them.
	if (dst->isNull()) {
	dst->setConfig(src->getConfig(), w, h);
	dst->setIsOpaque(src->isOpaque());

	if (!this->allocPixelRef(dst, NULL)) {
	SkDEBUGF(("failed to allocate pixels needed to crop the bitmap"));
	return false;
	}
	}
	// check to see if the destination is large enough to decode the desired
	// region. If this assert fails we will just draw as much of the source
	// into the destination that we can.
	if (dst->width() < w \|\| dst->height() < h) {
	SkDEBUGF(("SkImageDecoder::cropBitmap does not have a large enough bitmap.\n"));
	}

	// Set the Src_Mode for the paint to prevent transparency issue in the
	// dest in the event that the dest was being re-used.
	SkPaint paint;
	paint.setXfermodeMode(SkXfermode::kSrc_Mode);

	SkCanvas canvas(*dst);
	canvas.drawSprite(*src, (srcX - dstX) / sampleSize,
	(srcY - dstY) / sampleSize,
	&paint);
	return true;
	}

	///////////////////////////////////////////////////////////////////////////////

	bool SkImageDecoder::DecodeFile(const char file[], SkBitmap* bm,
	SkBitmap::Config pref, Mode mode, Format* format) {
	SkASSERT(file);
	SkASSERT(bm);

	SkAutoTUnref<SkStream> stream(SkStream::NewFromFile(file));
	if (stream.get()) {
	if (SkImageDecoder::DecodeStream(stream, bm, pref, mode, format)) {
	bm->pixelRef()->setURI(file);
	return true;
	}
	}
	return false;
	}

	bool SkImageDecoder::DecodeMemory(const void* buffer, size_t size, SkBitmap* bm,
	SkBitmap::Config pref, Mode mode, Format* format) {
	if (0 == size) {
	return false;
	}
	SkASSERT(buffer);

	SkMemoryStream stream(buffer, size);
	return SkImageDecoder::DecodeStream(&stream, bm, pref, mode, format);
	}

	/**
	* Special allocator used by DecodeMemoryToTarget. Uses preallocated memory
	* provided if the bm is 8888. Otherwise, uses a heap allocator. The same
	* allocator will be used again for a copy to 8888, when the preallocated
	* memory will be used.
	*/
	class TargetAllocator : public SkBitmap::HeapAllocator {

	public:
	TargetAllocator(void* target)
	: fTarget(target) {}

	virtual bool allocPixelRef(SkBitmap* bm, SkColorTable* ct) SK_OVERRIDE {
	// If the config is not 8888, allocate a pixelref using the heap.
	// fTarget will be used to store the final pixels when copied to
	// 8888.
	if (bm->config() != SkBitmap::kARGB_8888_Config) {
	return INHERITED::allocPixelRef(bm, ct);
	}
	// In kARGB_8888_Config, there is no colortable.
	SkASSERT(NULL == ct);
	bm->setPixels(fTarget);
	return true;
	}

	private:
	void* fTarget;
	typedef SkBitmap::HeapAllocator INHERITED;
	};

	/**
	* Helper function for DecodeMemoryToTarget. DecodeMemoryToTarget wants
	* 8888, so set the config to it. All parameters must not be null.
	* @param decoder Decoder appropriate for this stream.
	* @param stream Rewound stream to the encoded data.
	* @param bitmap On success, will have its bounds set to the bounds of the
	* encoded data, and its config set to 8888.
	* @return True if the bounds were decoded and the bitmap is 8888 or can be
	* copied to 8888.
	*/
	static bool decode_bounds_to_8888(SkImageDecoder* decoder, SkStream* stream,
	SkBitmap* bitmap) {
	SkASSERT(decoder != NULL);
	SkASSERT(stream != NULL);
	SkASSERT(bitmap != NULL);

	if (!decoder->decode(stream, bitmap, SkImageDecoder::kDecodeBounds_Mode)) {
	return false;
	}

	if (bitmap->config() == SkBitmap::kARGB_8888_Config) {
	return true;
	}

	if (!bitmap->canCopyTo(SkBitmap::kARGB_8888_Config)) {
	return false;
	}

	bitmap->setConfig(SkBitmap::kARGB_8888_Config, bitmap->width(), bitmap->height());
	return true;
	}

	/**
	* Helper function for DecodeMemoryToTarget. Decodes the stream into bitmap, and if
	* the bitmap is not 8888, then it is copied to 8888. Either way, the end result has
	* its pixels stored in target. All parameters must not be null.
	* @param decoder Decoder appropriate for this stream.
	* @param stream Rewound stream to the encoded data.
	* @param bitmap On success, will contain the decoded image, with its pixels stored
	* at target.
	* @param target Preallocated memory for storing pixels.
	* @return bool Whether the decode (and copy, if necessary) succeeded.
	*/
	static bool decode_pixels_to_8888(SkImageDecoder* decoder, SkStream* stream,
	SkBitmap* bitmap, void* target) {
	SkASSERT(decoder != NULL);
	SkASSERT(stream != NULL);
	SkASSERT(bitmap != NULL);
	SkASSERT(target != NULL);

	TargetAllocator allocator(target);
	decoder->setAllocator(&allocator);

	bool success = decoder->decode(stream, bitmap, SkImageDecoder::kDecodePixels_Mode);
	decoder->setAllocator(NULL);

	if (!success) {
	return false;
	}

	if (bitmap->config() == SkBitmap::kARGB_8888_Config) {
	return true;
	}

	SkBitmap bm8888;
	if (!bitmap->copyTo(&bm8888, SkBitmap::kARGB_8888_Config, &allocator)) {
	return false;
	}

	bitmap->swap(bm8888);
	return true;
	}

	bool SkImageDecoder::DecodeMemoryToTarget(const void* buffer, size_t size,
	SkImage::Info* info,
	const SkBitmapFactory::Target* target) {
	if (NULL == info) {
	return false;
	}

	// FIXME: Just to get this working, implement in terms of existing
	// ImageDecoder calls.
	SkBitmap bm;
	SkMemoryStream stream(buffer, size);
	SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(&stream));
	if (NULL == decoder.get()) {
	return false;
	}

	if (!decode_bounds_to_8888(decoder.get(), &stream, &bm)) {
	return false;
	}

	SkASSERT(bm.config() == SkBitmap::kARGB_8888_Config);

	// Now set info properly.
	// Since Config is SkBitmap::kARGB_8888_Config, SkBitmapToImageInfo
	// will always succeed.
	SkAssertResult(SkBitmapToImageInfo(bm, info));

	if (NULL == target) {
	return true;
	}

	if (target->fRowBytes != SkToU32(bm.rowBytes())) {
	if (target->fRowBytes < SkImageMinRowBytes(*info)) {
	SkASSERT(!"Desired row bytes is too small");
	return false;
	}
	bm.setConfig(bm.config(), bm.width(), bm.height(), target->fRowBytes);
	}

	// SkMemoryStream.rewind() will always return true.
	SkAssertResult(stream.rewind());
	return decode_pixels_to_8888(decoder.get(), &stream, &bm, target->fAddr);
	}


	bool SkImageDecoder::DecodeStream(SkStream* stream, SkBitmap* bm,
	SkBitmap::Config pref, Mode mode, Format* format) {
	SkASSERT(stream);
	SkASSERT(bm);

	bool success = false;
	SkImageDecoder* codec = SkImageDecoder::Factory(stream);

	if (NULL != codec) {
	success = codec->decode(stream, bm, pref, mode);
	if (success && format) {
	*format = codec->getFormat();
	if (kUnknown_Format == *format) {
	if (stream->rewind()) {
	*format = GetStreamFormat(stream);
	}
	}
	}
	delete codec;
	}
	return success;
	}

	/**
	* This function leaks, but that is okay because it is not intended
	* to be called. It is only here so that the linker will include the
	* decoders.
	* Make sure to keep it in sync with images.gyp, so only the encoders
	* which are created on a platform are linked.
	*/
	void force_linking();
	void force_linking() {
	SkASSERT(false);
	CreateJPEGImageDecoder();
	CreateWEBPImageDecoder();
	CreateBMPImageDecoder();
	CreateICOImageDecoder();
	CreateWBMPImageDecoder();
	// Only link GIF and PNG on platforms that build them. See images.gyp
	#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
	CreateGIFImageDecoder();
	#endif
	#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
	CreatePNGImageDecoder();
	#endif
	}