src/ports/SkImageDecoder_CG.cpp - platform/external/skia - Git at Google

 /*
  * Copyright 2008 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 "SkTypes.h"
 #if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)

 #include "SkCGUtils.h"
 #include "SkColorPriv.h"
 #include "SkData.h"
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkMovie.h"
 #include "SkStream.h"
 #include "SkStreamPriv.h"
 #include "SkTemplates.h"
 #include "SkUnPreMultiply.h"

 #ifdef SK_BUILD_FOR_MAC
 #include <ApplicationServices/ApplicationServices.h>
 #endif

 #ifdef SK_BUILD_FOR_IOS
 #include <CoreGraphics/CoreGraphics.h>
 #include <ImageIO/ImageIO.h>
 #include <MobileCoreServices/MobileCoreServices.h>
 #endif

 static void data_unref_proc(void* skdata, const void*, size_t) {
     SkASSERT(skdata);
     static_cast<SkData*>(skdata)->unref();
 }

 static CGDataProviderRef SkStreamToDataProvider(SkStream* stream) {
     // TODO: use callbacks, so we don't have to load all the data into RAM
     SkData* skdata = SkCopyStreamToData(stream);
     if (!skdata) {
         return nullptr;
     }

     return CGDataProviderCreateWithData(skdata, skdata->data(), skdata->size(), data_unref_proc);
 }

 static CGImageSourceRef SkStreamToCGImageSource(SkStream* stream) {
     CGDataProviderRef data = SkStreamToDataProvider(stream);
     if (!data) {
         return nullptr;
     }
     CGImageSourceRef imageSrc = CGImageSourceCreateWithDataProvider(data, 0);
     CGDataProviderRelease(data);
     return imageSrc;
 }

 class SkImageDecoder_CG : public SkImageDecoder {
 protected:
     virtual Result onDecode(SkStream* stream, SkBitmap* bm, Mode);
 };

 static void argb_4444_force_opaque(void* row, int count) {
     uint16_t* row16 = (uint16_t*)row;
     for (int i = 0; i < count; ++i) {
         row16[i] |= 0xF000;
     }
 }

 static void argb_8888_force_opaque(void* row, int count) {
     // can use RGBA or BGRA, they have the same shift for alpha
     const uint32_t alphaMask = 0xFF << SK_RGBA_A32_SHIFT;
     uint32_t* row32 = (uint32_t*)row;
     for (int i = 0; i < count; ++i) {
         row32[i] |= alphaMask;
     }
 }

 static void alpha_8_force_opaque(void* row, int count) {
     memset(row, 0xFF, count);
 }

 static void force_opaque(SkBitmap* bm) {
     SkAutoLockPixels alp(*bm);
     if (!bm->getPixels()) {
         return;
     }

     void (*proc)(void*, int);
     switch (bm->colorType()) {
         case kARGB_4444_SkColorType:
             proc = argb_4444_force_opaque;
             break;
         case kRGBA_8888_SkColorType:
         case kBGRA_8888_SkColorType:
             proc = argb_8888_force_opaque;
             break;
         case kAlpha_8_SkColorType:
             proc = alpha_8_force_opaque;
             break;
         default:
             return;
     }

     char* row = (char*)bm->getPixels();
     for (int y = 0; y < bm->height(); ++y) {
         proc(row, bm->width());
         row += bm->rowBytes();
     }
     bm->setAlphaType(kOpaque_SkAlphaType);
 }

 #define BITMAP_INFO (kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast)

 class AutoCFDataRelease {
     CFDataRef fDR;
 public:
     AutoCFDataRelease(CFDataRef dr) : fDR(dr) {}
     ~AutoCFDataRelease() { if (fDR) { CFRelease(fDR); } }

     operator CFDataRef () { return fDR; }
 };

 static bool colorspace_is_sRGB(CGColorSpaceRef cs) {
 #ifdef SK_BUILD_FOR_IOS
     return true;    // iOS seems to define itself to always return sRGB <reed>
 #else
     AutoCFDataRelease data(CGColorSpaceCopyICCProfile(cs));
     if (data) {
         // found by inspection -- need a cleaner way to sniff a profile
         const CFIndex ICC_PROFILE_OFFSET_TO_SRGB_TAG = 52;

         if (CFDataGetLength(data) >= ICC_PROFILE_OFFSET_TO_SRGB_TAG + 4) {
             return !memcmp(CFDataGetBytePtr(data) + ICC_PROFILE_OFFSET_TO_SRGB_TAG, "sRGB", 4);
         }
     }
     return false;
 #endif
 }

 SkImageDecoder::Result SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
     CGImageSourceRef imageSrc = SkStreamToCGImageSource(stream);

     if (nullptr == imageSrc) {
         return kFailure;
     }
     SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);

     CGImageRef image = CGImageSourceCreateImageAtIndex(imageSrc, 0, nullptr);
     if (nullptr == image) {
         return kFailure;
     }
     SkAutoTCallVProc<CGImage, CGImageRelease> arimage(image);

     const int width = SkToInt(CGImageGetWidth(image));
     const int height = SkToInt(CGImageGetHeight(image));
     SkColorProfileType cpType = kLinear_SkColorProfileType;

     CGColorSpaceRef cs = CGImageGetColorSpace(image);
     if (cs) {
         CGColorSpaceModel m = CGColorSpaceGetModel(cs);
         if (kCGColorSpaceModelRGB == m && colorspace_is_sRGB(cs)) {
             cpType = kSRGB_SkColorProfileType;
         }
     }

     SkAlphaType at = kPremul_SkAlphaType;
     switch (CGImageGetAlphaInfo(image)) {
         case kCGImageAlphaNone:
         case kCGImageAlphaNoneSkipLast:
         case kCGImageAlphaNoneSkipFirst:
             at = kOpaque_SkAlphaType;
             break;
         default:
             break;
     }

     bm->setInfo(SkImageInfo::Make(width, height, kN32_SkColorType, at, cpType));
     if (SkImageDecoder::kDecodeBounds_Mode == mode) {
         return kSuccess;
     }

     if (!this->allocPixelRef(bm, nullptr)) {
         return kFailure;
     }

     SkAutoLockPixels alp(*bm);

     if (!SkCopyPixelsFromCGImage(bm->info(), bm->rowBytes(), bm->getPixels(), image)) {
         return kFailure;
     }

     CGImageAlphaInfo info = CGImageGetAlphaInfo(image);
     switch (info) {
         case kCGImageAlphaNone:
         case kCGImageAlphaNoneSkipLast:
         case kCGImageAlphaNoneSkipFirst:
             // We're opaque, but we can't rely on the data always having 0xFF
             // in the alpha slot (which Skia wants), so we have to ram it in
             // ourselves.
             force_opaque(bm);
             break;
         default:
             // we don't know if we're opaque or not, so compute it.
             if (SkBitmap::ComputeIsOpaque(*bm)) {
                 bm->setAlphaType(kOpaque_SkAlphaType);
             }
     }
     if (!bm->isOpaque() && this->getRequireUnpremultipliedColors()) {
         // CGBitmapContext does not support unpremultiplied, so the image has been premultiplied.
         // Convert to unpremultiplied.
         for (int i = 0; i < width; ++i) {
             for (int j = 0; j < height; ++j) {
                 uint32_t* addr = bm->getAddr32(i, j);
                 *addr = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(*addr);
             }
         }
         bm->setAlphaType(kUnpremul_SkAlphaType);
     }
     return kSuccess;
 }

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

 extern SkImageDecoder* image_decoder_from_stream(SkStreamRewindable*);

 SkImageDecoder* SkImageDecoder::Factory(SkStreamRewindable* stream) {
     SkImageDecoder* decoder = image_decoder_from_stream(stream);
     if (nullptr == decoder) {
         // If no image decoder specific to the stream exists, use SkImageDecoder_CG.
         return new SkImageDecoder_CG;
     } else {
         return decoder;
     }
 }

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

 SkMovie* SkMovie::DecodeStream(SkStreamRewindable* stream) {
     return nullptr;
 }

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

 static size_t consumer_put(void* info, const void* buffer, size_t count) {
     SkWStream* stream = reinterpret_cast<SkWStream*>(info);
     return stream->write(buffer, count) ? count : 0;
 }

 static void consumer_release(void* info) {
     // we do nothing, since by design we don't "own" the stream (i.e. info)
 }

 static CGDataConsumerRef SkStreamToCGDataConsumer(SkWStream* stream) {
     CGDataConsumerCallbacks procs;
     procs.putBytes = consumer_put;
     procs.releaseConsumer = consumer_release;
     // we don't own/reference the stream, so it our consumer must not live
     // longer that our caller's ownership of the stream
     return CGDataConsumerCreate(stream, &procs);
 }

 static CGImageDestinationRef SkStreamToImageDestination(SkWStream* stream,
                                                         CFStringRef type) {
     CGDataConsumerRef consumer = SkStreamToCGDataConsumer(stream);
     if (nullptr == consumer) {
         return nullptr;
     }
     SkAutoTCallVProc<const void, CFRelease> arconsumer(consumer);

     return CGImageDestinationCreateWithDataConsumer(consumer, type, 1, nullptr);
 }

 class SkImageEncoder_CG : public SkImageEncoder {
 public:
     SkImageEncoder_CG(Type t) : fType(t) {}

 protected:
     virtual bool onEncode(SkWStream* stream, const SkBitmap& bm, int quality);

 private:
     Type fType;
 };

 /*  Encode bitmaps via CGImageDestination. We setup a DataConsumer which writes
     to our SkWStream. Since we don't reference/own the SkWStream, our consumer
     must only live for the duration of the onEncode() method.
  */
 bool SkImageEncoder_CG::onEncode(SkWStream* stream, const SkBitmap& bm,
                                  int quality) {
     // Used for converting a bitmap to 8888.
     const SkBitmap* bmPtr = &bm;
     SkBitmap bitmap8888;

     CFStringRef type;
     switch (fType) {
         case kICO_Type:
             type = kUTTypeICO;
             break;
         case kBMP_Type:
             type = kUTTypeBMP;
             break;
         case kGIF_Type:
             type = kUTTypeGIF;
             break;
         case kJPEG_Type:
             type = kUTTypeJPEG;
             break;
         case kPNG_Type:
             // PNG encoding an ARGB_4444 bitmap gives the following errors in GM:
             // <Error>: CGImageDestinationAddImage image could not be converted to destination
             // format.
             // <Error>: CGImageDestinationFinalize image destination does not have enough images
             // So instead we copy to 8888.
             if (bm.colorType() == kARGB_4444_SkColorType) {
                 bm.copyTo(&bitmap8888, kN32_SkColorType);
                 bmPtr = &bitmap8888;
             }
             type = kUTTypePNG;
             break;
         default:
             return false;
     }

     CGImageDestinationRef dst = SkStreamToImageDestination(stream, type);
     if (nullptr == dst) {
         return false;
     }
     SkAutoTCallVProc<const void, CFRelease> ardst(dst);

     CGImageRef image = SkCreateCGImageRef(*bmPtr);
     if (nullptr == image) {
         return false;
     }
     SkAutoTCallVProc<CGImage, CGImageRelease> agimage(image);

     CGImageDestinationAddImage(dst, image, nullptr);
     return CGImageDestinationFinalize(dst);
 }

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

 static SkImageEncoder* sk_imageencoder_cg_factory(SkImageEncoder::Type t) {
     switch (t) {
         case SkImageEncoder::kICO_Type:
         case SkImageEncoder::kBMP_Type:
         case SkImageEncoder::kGIF_Type:
         case SkImageEncoder::kJPEG_Type:
         case SkImageEncoder::kPNG_Type:
             break;
         default:
             return nullptr;
     }
     return new SkImageEncoder_CG(t);
 }

 static SkImageEncoder_EncodeReg gEReg(sk_imageencoder_cg_factory);

 #ifdef SK_BUILD_FOR_IOS
 class SkPNGImageEncoder_IOS : public SkImageEncoder_CG {
 public:
     SkPNGImageEncoder_IOS()
         : SkImageEncoder_CG(kPNG_Type) {
     }
 };

 DEFINE_ENCODER_CREATOR(PNGImageEncoder_IOS);
 #endif

 struct FormatConversion {
     CFStringRef             fUTType;
     SkImageDecoder::Format  fFormat;
 };

 // Array of the types supported by the decoder.
 static const FormatConversion gFormatConversions[] = {
     { kUTTypeBMP, SkImageDecoder::kBMP_Format },
     { kUTTypeGIF, SkImageDecoder::kGIF_Format },
     { kUTTypeICO, SkImageDecoder::kICO_Format },
     { kUTTypeJPEG, SkImageDecoder::kJPEG_Format },
     // Also include JPEG2000
     { kUTTypeJPEG2000, SkImageDecoder::kJPEG_Format },
     { kUTTypePNG, SkImageDecoder::kPNG_Format },
 };

 static SkImageDecoder::Format UTType_to_Format(const CFStringRef uttype) {
     for (size_t i = 0; i < SK_ARRAY_COUNT(gFormatConversions); i++) {
         if (CFStringCompare(uttype, gFormatConversions[i].fUTType, 0) == kCFCompareEqualTo) {
             return gFormatConversions[i].fFormat;
         }
     }
     return SkImageDecoder::kUnknown_Format;
 }

 static SkImageDecoder::Format get_format_cg(SkStreamRewindable* stream) {
     CGImageSourceRef imageSrc = SkStreamToCGImageSource(stream);

     if (nullptr == imageSrc) {
         return SkImageDecoder::kUnknown_Format;
     }

     SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);
     const CFStringRef name = CGImageSourceGetType(imageSrc);
     if (nullptr == name) {
         return SkImageDecoder::kUnknown_Format;
     }
     return UTType_to_Format(name);
 }

 static SkImageDecoder_FormatReg gFormatReg(get_format_cg);

 #endif//defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)
	/*
	* Copyright 2008 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 "SkTypes.h"
	#if defined(SK_BUILD_FOR_MAC) \|\| defined(SK_BUILD_FOR_IOS)

	#include "SkCGUtils.h"
	#include "SkColorPriv.h"
	#include "SkData.h"
	#include "SkImageDecoder.h"
	#include "SkImageEncoder.h"
	#include "SkMovie.h"
	#include "SkStream.h"
	#include "SkStreamPriv.h"
	#include "SkTemplates.h"
	#include "SkUnPreMultiply.h"

	#ifdef SK_BUILD_FOR_MAC
	#include <ApplicationServices/ApplicationServices.h>
	#endif

	#ifdef SK_BUILD_FOR_IOS
	#include <CoreGraphics/CoreGraphics.h>
	#include <ImageIO/ImageIO.h>
	#include <MobileCoreServices/MobileCoreServices.h>
	#endif

	static void data_unref_proc(void* skdata, const void*, size_t) {
	SkASSERT(skdata);
	static_cast<SkData*>(skdata)->unref();
	}

	static CGDataProviderRef SkStreamToDataProvider(SkStream* stream) {
	// TODO: use callbacks, so we don't have to load all the data into RAM
	SkData* skdata = SkCopyStreamToData(stream);
	if (!skdata) {
	return nullptr;
	}

	return CGDataProviderCreateWithData(skdata, skdata->data(), skdata->size(), data_unref_proc);
	}

	static CGImageSourceRef SkStreamToCGImageSource(SkStream* stream) {
	CGDataProviderRef data = SkStreamToDataProvider(stream);
	if (!data) {
	return nullptr;
	}
	CGImageSourceRef imageSrc = CGImageSourceCreateWithDataProvider(data, 0);
	CGDataProviderRelease(data);
	return imageSrc;
	}

	class SkImageDecoder_CG : public SkImageDecoder {
	protected:
	virtual Result onDecode(SkStream* stream, SkBitmap* bm, Mode);
	};

	static void argb_4444_force_opaque(void* row, int count) {
	uint16_t* row16 = (uint16_t*)row;
	for (int i = 0; i < count; ++i) {
	row16[i] \|= 0xF000;
	}
	}

	static void argb_8888_force_opaque(void* row, int count) {
	// can use RGBA or BGRA, they have the same shift for alpha
	const uint32_t alphaMask = 0xFF << SK_RGBA_A32_SHIFT;
	uint32_t* row32 = (uint32_t*)row;
	for (int i = 0; i < count; ++i) {
	row32[i] \|= alphaMask;
	}
	}

	static void alpha_8_force_opaque(void* row, int count) {
	memset(row, 0xFF, count);
	}

	static void force_opaque(SkBitmap* bm) {
	SkAutoLockPixels alp(*bm);
	if (!bm->getPixels()) {
	return;
	}

	void (proc)(void, int);
	switch (bm->colorType()) {
	case kARGB_4444_SkColorType:
	proc = argb_4444_force_opaque;
	break;
	case kRGBA_8888_SkColorType:
	case kBGRA_8888_SkColorType:
	proc = argb_8888_force_opaque;
	break;
	case kAlpha_8_SkColorType:
	proc = alpha_8_force_opaque;
	break;
	default:
	return;
	}

	char* row = (char*)bm->getPixels();
	for (int y = 0; y < bm->height(); ++y) {
	proc(row, bm->width());
	row += bm->rowBytes();
	}
	bm->setAlphaType(kOpaque_SkAlphaType);
	}

	#define BITMAP_INFO (kCGBitmapByteOrder32Big \| kCGImageAlphaPremultipliedLast)

	class AutoCFDataRelease {
	CFDataRef fDR;
	public:
	AutoCFDataRelease(CFDataRef dr) : fDR(dr) {}
	~AutoCFDataRelease() { if (fDR) { CFRelease(fDR); } }

	operator CFDataRef () { return fDR; }
	};

	static bool colorspace_is_sRGB(CGColorSpaceRef cs) {
	#ifdef SK_BUILD_FOR_IOS
	return true; // iOS seems to define itself to always return sRGB <reed>
	#else
	AutoCFDataRelease data(CGColorSpaceCopyICCProfile(cs));
	if (data) {
	// found by inspection -- need a cleaner way to sniff a profile
	const CFIndex ICC_PROFILE_OFFSET_TO_SRGB_TAG = 52;

	if (CFDataGetLength(data) >= ICC_PROFILE_OFFSET_TO_SRGB_TAG + 4) {
	return !memcmp(CFDataGetBytePtr(data) + ICC_PROFILE_OFFSET_TO_SRGB_TAG, "sRGB", 4);
	}
	}
	return false;
	#endif
	}

	SkImageDecoder::Result SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
	CGImageSourceRef imageSrc = SkStreamToCGImageSource(stream);

	if (nullptr == imageSrc) {
	return kFailure;
	}
	SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);

	CGImageRef image = CGImageSourceCreateImageAtIndex(imageSrc, 0, nullptr);
	if (nullptr == image) {
	return kFailure;
	}
	SkAutoTCallVProc<CGImage, CGImageRelease> arimage(image);

	const int width = SkToInt(CGImageGetWidth(image));
	const int height = SkToInt(CGImageGetHeight(image));
	SkColorProfileType cpType = kLinear_SkColorProfileType;

	CGColorSpaceRef cs = CGImageGetColorSpace(image);
	if (cs) {
	CGColorSpaceModel m = CGColorSpaceGetModel(cs);
	if (kCGColorSpaceModelRGB == m && colorspace_is_sRGB(cs)) {
	cpType = kSRGB_SkColorProfileType;
	}
	}

	SkAlphaType at = kPremul_SkAlphaType;
	switch (CGImageGetAlphaInfo(image)) {
	case kCGImageAlphaNone:
	case kCGImageAlphaNoneSkipLast:
	case kCGImageAlphaNoneSkipFirst:
	at = kOpaque_SkAlphaType;
	break;
	default:
	break;
	}

	bm->setInfo(SkImageInfo::Make(width, height, kN32_SkColorType, at, cpType));
	if (SkImageDecoder::kDecodeBounds_Mode == mode) {
	return kSuccess;
	}

	if (!this->allocPixelRef(bm, nullptr)) {
	return kFailure;
	}

	SkAutoLockPixels alp(*bm);

	if (!SkCopyPixelsFromCGImage(bm->info(), bm->rowBytes(), bm->getPixels(), image)) {
	return kFailure;
	}

	CGImageAlphaInfo info = CGImageGetAlphaInfo(image);
	switch (info) {
	case kCGImageAlphaNone:
	case kCGImageAlphaNoneSkipLast:
	case kCGImageAlphaNoneSkipFirst:
	// We're opaque, but we can't rely on the data always having 0xFF
	// in the alpha slot (which Skia wants), so we have to ram it in
	// ourselves.
	force_opaque(bm);
	break;
	default:
	// we don't know if we're opaque or not, so compute it.
	if (SkBitmap::ComputeIsOpaque(*bm)) {
	bm->setAlphaType(kOpaque_SkAlphaType);
	}
	}
	if (!bm->isOpaque() && this->getRequireUnpremultipliedColors()) {
	// CGBitmapContext does not support unpremultiplied, so the image has been premultiplied.
	// Convert to unpremultiplied.
	for (int i = 0; i < width; ++i) {
	for (int j = 0; j < height; ++j) {
	uint32_t* addr = bm->getAddr32(i, j);
	addr = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(addr);
	}
	}
	bm->setAlphaType(kUnpremul_SkAlphaType);
	}
	return kSuccess;
	}

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

	extern SkImageDecoder* image_decoder_from_stream(SkStreamRewindable*);

	SkImageDecoder* SkImageDecoder::Factory(SkStreamRewindable* stream) {
	SkImageDecoder* decoder = image_decoder_from_stream(stream);
	if (nullptr == decoder) {
	// If no image decoder specific to the stream exists, use SkImageDecoder_CG.
	return new SkImageDecoder_CG;
	} else {
	return decoder;
	}
	}

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

	SkMovie* SkMovie::DecodeStream(SkStreamRewindable* stream) {
	return nullptr;
	}

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

	static size_t consumer_put(void* info, const void* buffer, size_t count) {
	SkWStream* stream = reinterpret_cast<SkWStream*>(info);
	return stream->write(buffer, count) ? count : 0;
	}

	static void consumer_release(void* info) {
	// we do nothing, since by design we don't "own" the stream (i.e. info)
	}

	static CGDataConsumerRef SkStreamToCGDataConsumer(SkWStream* stream) {
	CGDataConsumerCallbacks procs;
	procs.putBytes = consumer_put;
	procs.releaseConsumer = consumer_release;
	// we don't own/reference the stream, so it our consumer must not live
	// longer that our caller's ownership of the stream
	return CGDataConsumerCreate(stream, &procs);
	}

	static CGImageDestinationRef SkStreamToImageDestination(SkWStream* stream,
	CFStringRef type) {
	CGDataConsumerRef consumer = SkStreamToCGDataConsumer(stream);
	if (nullptr == consumer) {
	return nullptr;
	}
	SkAutoTCallVProc<const void, CFRelease> arconsumer(consumer);

	return CGImageDestinationCreateWithDataConsumer(consumer, type, 1, nullptr);
	}

	class SkImageEncoder_CG : public SkImageEncoder {
	public:
	SkImageEncoder_CG(Type t) : fType(t) {}

	protected:
	virtual bool onEncode(SkWStream* stream, const SkBitmap& bm, int quality);

	private:
	Type fType;
	};

	/* Encode bitmaps via CGImageDestination. We setup a DataConsumer which writes
	to our SkWStream. Since we don't reference/own the SkWStream, our consumer
	must only live for the duration of the onEncode() method.
	*/
	bool SkImageEncoder_CG::onEncode(SkWStream* stream, const SkBitmap& bm,
	int quality) {
	// Used for converting a bitmap to 8888.
	const SkBitmap* bmPtr = &bm;
	SkBitmap bitmap8888;

	CFStringRef type;
	switch (fType) {
	case kICO_Type:
	type = kUTTypeICO;
	break;
	case kBMP_Type:
	type = kUTTypeBMP;
	break;
	case kGIF_Type:
	type = kUTTypeGIF;
	break;
	case kJPEG_Type:
	type = kUTTypeJPEG;
	break;
	case kPNG_Type:
	// PNG encoding an ARGB_4444 bitmap gives the following errors in GM:
	// <Error>: CGImageDestinationAddImage image could not be converted to destination
	// format.
	// <Error>: CGImageDestinationFinalize image destination does not have enough images
	// So instead we copy to 8888.
	if (bm.colorType() == kARGB_4444_SkColorType) {
	bm.copyTo(&bitmap8888, kN32_SkColorType);
	bmPtr = &bitmap8888;
	}
	type = kUTTypePNG;
	break;
	default:
	return false;
	}

	CGImageDestinationRef dst = SkStreamToImageDestination(stream, type);
	if (nullptr == dst) {
	return false;
	}
	SkAutoTCallVProc<const void, CFRelease> ardst(dst);

	CGImageRef image = SkCreateCGImageRef(*bmPtr);
	if (nullptr == image) {
	return false;
	}
	SkAutoTCallVProc<CGImage, CGImageRelease> agimage(image);

	CGImageDestinationAddImage(dst, image, nullptr);
	return CGImageDestinationFinalize(dst);
	}

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

	static SkImageEncoder* sk_imageencoder_cg_factory(SkImageEncoder::Type t) {
	switch (t) {
	case SkImageEncoder::kICO_Type:
	case SkImageEncoder::kBMP_Type:
	case SkImageEncoder::kGIF_Type:
	case SkImageEncoder::kJPEG_Type:
	case SkImageEncoder::kPNG_Type:
	break;
	default:
	return nullptr;
	}
	return new SkImageEncoder_CG(t);
	}

	static SkImageEncoder_EncodeReg gEReg(sk_imageencoder_cg_factory);

	#ifdef SK_BUILD_FOR_IOS
	class SkPNGImageEncoder_IOS : public SkImageEncoder_CG {
	public:
	SkPNGImageEncoder_IOS()
	: SkImageEncoder_CG(kPNG_Type) {
	}
	};

	DEFINE_ENCODER_CREATOR(PNGImageEncoder_IOS);
	#endif

	struct FormatConversion {
	CFStringRef fUTType;
	SkImageDecoder::Format fFormat;
	};

	// Array of the types supported by the decoder.
	static const FormatConversion gFormatConversions[] = {
	{ kUTTypeBMP, SkImageDecoder::kBMP_Format },
	{ kUTTypeGIF, SkImageDecoder::kGIF_Format },
	{ kUTTypeICO, SkImageDecoder::kICO_Format },
	{ kUTTypeJPEG, SkImageDecoder::kJPEG_Format },
	// Also include JPEG2000
	{ kUTTypeJPEG2000, SkImageDecoder::kJPEG_Format },
	{ kUTTypePNG, SkImageDecoder::kPNG_Format },
	};

	static SkImageDecoder::Format UTType_to_Format(const CFStringRef uttype) {
	for (size_t i = 0; i < SK_ARRAY_COUNT(gFormatConversions); i++) {
	if (CFStringCompare(uttype, gFormatConversions[i].fUTType, 0) == kCFCompareEqualTo) {
	return gFormatConversions[i].fFormat;
	}
	}
	return SkImageDecoder::kUnknown_Format;
	}

	static SkImageDecoder::Format get_format_cg(SkStreamRewindable* stream) {
	CGImageSourceRef imageSrc = SkStreamToCGImageSource(stream);

	if (nullptr == imageSrc) {
	return SkImageDecoder::kUnknown_Format;
	}

	SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);
	const CFStringRef name = CGImageSourceGetType(imageSrc);
	if (nullptr == name) {
	return SkImageDecoder::kUnknown_Format;
	}
	return UTType_to_Format(name);
	}

	static SkImageDecoder_FormatReg gFormatReg(get_format_cg);

	#endif//defined(SK_BUILD_FOR_MAC) \|\| defined(SK_BUILD_FOR_IOS)