gm/exoticformats.cpp - platform/external/skia - Gitiles

 /*
  * Copyright 2020 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "gm/gm.h"
 #include "include/core/SkCanvas.h"
 #include "include/core/SkImage.h"
 #include "include/core/SkStream.h"
 #include "src/core/SkCompressedDataUtils.h"
 #include "src/core/SkMipMap.h"
 #include "src/gpu/GrContextPriv.h"
 #include "src/gpu/gl/GrGLDefines.h"
 #include "src/image/SkImage_Base.h"

 #include "tools/Resources.h"

 //-------------------------------------------------------------------------------------------------
 struct ImageInfo {
     SkISize                  fDim;
     GrMipMapped              fMipMapped;
     SkImage::CompressionType fCompressionType;
 };

 /*
  * Get an int from a buffer
  * This method is unsafe, the caller is responsible for performing a check
  */
 static inline uint32_t get_uint(uint8_t* buffer, uint32_t i) {
     uint32_t result;
     memcpy(&result, &(buffer[i]), 4);
     return result;
 }

 // This KTX loader is barely sufficient to load the specific files this GM requires. Use
 // at your own peril.
 static sk_sp<SkData> load_ktx(const char* filename, ImageInfo* imageInfo) {
     SkFILEStream input(filename);
     if (!input.isValid()) {
         return nullptr;
     }

     constexpr int kKTXIdentifierSize = 12;
     constexpr int kKTXHeaderSize = kKTXIdentifierSize + 13 * sizeof(uint32_t);
     uint8_t header[kKTXHeaderSize];

     if (input.read(header, kKTXHeaderSize) != kKTXHeaderSize) {
         return nullptr;
     }

     static const uint8_t kExpectedIdentifier[kKTXIdentifierSize] = {
         0xAB, 0x4B, 0x54, 0x58, 0x20, 0x31, 0x31, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A
     };

     if (memcmp(header, kExpectedIdentifier, kKTXIdentifierSize)) {
         return nullptr;
     }

     uint32_t endianness = get_uint(header, 12);
     if (endianness != 0x04030201) {
         // TODO: need to swap rest of header and, if glTypeSize is > 1, all
         // the texture data.
         return nullptr;
     }

     uint32_t glType = get_uint(header, 16);
     SkDEBUGCODE(uint32_t glTypeSize = get_uint(header, 20);)
     uint32_t glFormat = get_uint(header, 24);
     uint32_t glInternalFormat = get_uint(header, 28);
     //uint32_t glBaseInternalFormat = get_uint(header, 32);
     uint32_t pixelWidth = get_uint(header, 36);
     uint32_t pixelHeight = get_uint(header, 40);
     uint32_t pixelDepth = get_uint(header, 44);
     //uint32_t numberOfArrayElements = get_uint(header, 48);
     uint32_t numberOfFaces = get_uint(header, 52);
     int numberOfMipmapLevels = get_uint(header, 56);
     uint32_t bytesOfKeyValueData = get_uint(header, 60);

     if (glType != 0 || glFormat != 0) {  // only care about compressed data for now
         return nullptr;
     }
     SkASSERT(glTypeSize == 1); // required for compressed data

     // We only handle these four formats right now
     switch (glInternalFormat) {
         case GR_GL_COMPRESSED_ETC1_RGB8:
         case GR_GL_COMPRESSED_RGB8_ETC2:
             imageInfo->fCompressionType = SkImage::CompressionType::kETC2_RGB8_UNORM;
             break;
         case GR_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
             imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGB8_UNORM;
             break;
         case GR_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
             imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGBA8_UNORM;
             break;
         default:
             return nullptr;
     }

     imageInfo->fDim.fWidth = pixelWidth;
     imageInfo->fDim.fHeight = pixelHeight;

     if (pixelDepth != 0) {
         return nullptr; // pixel depth is always zero for 2D textures
     }

     if (numberOfFaces != 1) {
         return nullptr; // we don't support cube maps right now
     }

     if (numberOfMipmapLevels == 1) {
         imageInfo->fMipMapped = GrMipMapped::kNo;
     } else {
         int numRequiredMipLevels = SkMipMap::ComputeLevelCount(pixelWidth, pixelHeight)+1;
         if (numberOfMipmapLevels != numRequiredMipLevels) {
             return nullptr;
         }
         imageInfo->fMipMapped = GrMipMapped::kYes;
     }

     if (bytesOfKeyValueData != 0) {
         return nullptr;
     }

     SkTArray<size_t> individualMipOffsets(numberOfMipmapLevels);

     size_t dataSize = SkCompressedDataSize(imageInfo->fCompressionType,
                                            { (int) pixelWidth, (int) pixelHeight },
                                            &individualMipOffsets,
                                            imageInfo->fMipMapped == GrMipMapped::kYes);
     SkASSERT(individualMipOffsets.size() == (size_t) numberOfMipmapLevels);

     sk_sp<SkData> data = SkData::MakeUninitialized(dataSize);

     uint8_t* dest = (uint8_t*) data->writable_data();

     size_t offset = 0;
     for (int i = 0; i < numberOfMipmapLevels; ++i) {
         uint32_t imageSize;

         if (input.read(&imageSize, 4) != 4) {
             return nullptr;
         }

         SkASSERT(offset + imageSize <= dataSize);
         SkASSERT(offset == individualMipOffsets[i]);

         if (input.read(&dest[offset], imageSize) != imageSize) {
             return nullptr;
         }

         offset += imageSize;
     }

     return data;
 }

 //-------------------------------------------------------------------------------------------------
 typedef uint32_t DWORD;

 // Values for the DDS_PIXELFORMAT 'dwFlags' field
 constexpr unsigned int kDDPF_FOURCC      = 0x4;

 struct DDS_PIXELFORMAT {
     DWORD dwSize;
     DWORD dwFlags;
     DWORD dwFourCC;
     DWORD dwRGBBitCount;
     DWORD dwRBitMask;
     DWORD dwGBitMask;
     DWORD dwBBitMask;
     DWORD dwABitMask;
 };

 // Values for the DDS_HEADER 'dwFlags' field
 constexpr unsigned int kDDSD_CAPS        = 0x1;        // required
 constexpr unsigned int kDDSD_HEIGHT      = 0x2;        // required
 constexpr unsigned int kDDSD_WIDTH       = 0x4;        // required
 constexpr unsigned int kDDSD_PITCH       = 0x8;
 constexpr unsigned int kDDSD_PIXELFORMAT = 0x001000;   // required
 constexpr unsigned int kDDSD_MIPMAPCOUNT = 0x020000;
 constexpr unsigned int kDDSD_LINEARSIZE  = 0x080000;
 constexpr unsigned int kDDSD_DEPTH       = 0x800000;

 constexpr unsigned int kDDSD_REQUIRED = kDDSD_CAPS | kDDSD_HEIGHT | kDDSD_WIDTH | kDDSD_PIXELFORMAT;

 typedef struct {
     DWORD           dwSize;
     DWORD           dwFlags;
     DWORD           dwHeight;
     DWORD           dwWidth;
     DWORD           dwPitchOrLinearSize;
     DWORD           dwDepth;
     DWORD           dwMipMapCount;
     DWORD           dwReserved1[11];
     DDS_PIXELFORMAT ddspf;
     DWORD           dwCaps;
     DWORD           dwCaps2;
     DWORD           dwCaps3;
     DWORD           dwCaps4;
     DWORD           dwReserved2;
 } DDS_HEADER;

 // This DDS loader is barely sufficient to load the specific files this GM requires. Use
 // at your own peril.
 static sk_sp<SkData> load_dds(const char* filename, ImageInfo* imageInfo) {
     SkFILEStream input(filename);
     if (!input.isValid()) {
         return nullptr;
     }

     constexpr uint32_t kMagic = 0x20534444;
     uint32_t magic;

     if (input.read(&magic, 4) != 4) {
         return nullptr;
     }

     if (magic != kMagic) {
         return nullptr;
     }

     constexpr size_t kDDSHeaderSize = sizeof(DDS_HEADER);
     static_assert(kDDSHeaderSize == 124);
     constexpr size_t kDDSPixelFormatSize = sizeof(DDS_PIXELFORMAT);
     static_assert(kDDSPixelFormatSize == 32);

     DDS_HEADER header;

     if (input.read(&header, kDDSHeaderSize) != kDDSHeaderSize) {
         return nullptr;
     }

     if (header.dwSize != kDDSHeaderSize ||
         header.ddspf.dwSize != kDDSPixelFormatSize) {
         return nullptr;
     }

     if ((header.dwFlags & kDDSD_REQUIRED) != kDDSD_REQUIRED) {
         return nullptr;
     }

     if (header.dwFlags & (kDDSD_PITCH | kDDSD_LINEARSIZE | kDDSD_DEPTH)) {
         // TODO: support these features
     }

     imageInfo->fDim.fWidth = header.dwWidth;
     imageInfo->fDim.fHeight = header.dwHeight;

     int numberOfMipmapLevels = 1;
     if (header.dwFlags & kDDSD_MIPMAPCOUNT) {
         if (header.dwMipMapCount == 1) {
             imageInfo->fMipMapped = GrMipMapped::kNo;
         } else {
             int numRequiredLevels = SkMipMap::ComputeLevelCount(header.dwWidth, header.dwHeight)+1;
             if (header.dwMipMapCount != (unsigned) numRequiredLevels) {
                 return nullptr;
             }
             imageInfo->fMipMapped = GrMipMapped::kYes;
             numberOfMipmapLevels = numRequiredLevels;
         }
     } else {
         imageInfo->fMipMapped = GrMipMapped::kNo;
     }

     if (!(header.ddspf.dwFlags & kDDPF_FOURCC)) {
         return nullptr;
     }

     // We only handle these one format right now
     switch (header.ddspf.dwFourCC) {
         case 0x31545844: // DXT1
             imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGB8_UNORM;
             break;
         default:
             return nullptr;
     }

     SkTArray<size_t> individualMipOffsets(numberOfMipmapLevels);

     size_t dataSize = SkCompressedDataSize(imageInfo->fCompressionType,
                                            { (int) header.dwWidth, (int) header.dwHeight },
                                            &individualMipOffsets,
                                            imageInfo->fMipMapped == GrMipMapped::kYes);
     SkASSERT(individualMipOffsets.size() == (size_t) numberOfMipmapLevels);

     sk_sp<SkData> data = SkData::MakeUninitialized(dataSize);

     uint8_t* dest = (uint8_t*) data->writable_data();

     size_t amountRead = input.read(dest, dataSize);
     if (amountRead != dataSize) {
         return nullptr;
     }

     return data;
 }

 //-------------------------------------------------------------------------------------------------
 static sk_sp<SkImage> data_to_img(GrContext *context, sk_sp<SkData> data, const ImageInfo& info) {
     if (context) {
         return SkImage::MakeTextureFromCompressed(context, std::move(data),
                                                   info.fDim.fWidth,
                                                   info.fDim.fHeight,
                                                   info.fCompressionType,
                                                   info.fMipMapped);
     } else {
         return SkImage::MakeRasterFromCompressed(std::move(data),
                                                  info.fDim.fWidth,
                                                  info.fDim.fHeight,
                                                  info.fCompressionType);
     }
 }

 namespace skiagm {

 // This GM exercises our handling of some of the more exotic formats using externally
 // generated content. Right now it only tests ETC1 and BC1.
 class ExoticFormatsGM : public GM {
 public:
     ExoticFormatsGM() {
         this->setBGColor(SK_ColorBLACK);
     }

 protected:
     SkString onShortName() override {
         return SkString("exoticformats");
     }

     SkISize onISize() override {
         return SkISize::Make(2*kImgWidthHeight + 3 * kPad, kImgWidthHeight + 2 * kPad);
     }

     void loadImages(GrContext *context) {

         if (!fETC1Image) {
             ImageInfo info;
             sk_sp<SkData> data = load_ktx(GetResourcePath("images/flower-etc1.ktx").c_str(), &info);
             if (data) {
                 SkASSERT(info.fDim.equals(kImgWidthHeight, kImgWidthHeight));
                 SkASSERT(info.fMipMapped == GrMipMapped::kNo);
                 SkASSERT(info.fCompressionType == SkImage::CompressionType::kETC2_RGB8_UNORM);

                 fETC1Image = data_to_img(context, std::move(data), info);
             } else {
                 SkDebugf("failed to load flower-etc1.ktx\n");
             }
         }

         if (!fBC1Image) {
             ImageInfo info;
             sk_sp<SkData> data = load_dds(GetResourcePath("images/flower-bc1.dds").c_str(), &info);
             if (data) {
                 SkASSERT(info.fDim.equals(kImgWidthHeight, kImgWidthHeight));
                 SkASSERT(info.fMipMapped == GrMipMapped::kNo);
                 SkASSERT(info.fCompressionType == SkImage::CompressionType::kBC1_RGB8_UNORM);

                 fBC1Image = data_to_img(context, std::move(data), info);
             } else {
                 SkDebugf("failed to load flower-bc1.dds\n");
             }
         }

     }

     void drawImage(GrContext* context, SkCanvas* canvas, SkImage* image, int x, int y) {
         if (!image) {
             return;
         }

         bool isCompressed = false;
         if (image->isTextureBacked()) {
             const GrCaps* caps = context->priv().caps();

             GrTextureProxy* proxy = as_IB(image)->peekProxy();
             isCompressed = caps->isFormatCompressed(proxy->backendFormat());
         }

         canvas->drawImage(image, x, y);

         if (!isCompressed) {
             // Make it obvious which drawImages used decompressed images
             SkRect r = SkRect::MakeXYWH(x, y, kImgWidthHeight, kImgWidthHeight);
             SkPaint paint;
             paint.setColor(SK_ColorRED);
             paint.setStyle(SkPaint::kStroke_Style);
             paint.setStrokeWidth(2.0f);
             canvas->drawRect(r, paint);
         }
     }

     void onDraw(SkCanvas* canvas) override {
         GrContext* context = canvas->getGrContext();

         this->loadImages(context);

         this->drawImage(context, canvas, fETC1Image.get(), kPad, kPad);
         this->drawImage(context, canvas, fBC1Image.get(), kImgWidthHeight + 2 * kPad, kPad);
     }

 private:
     static const int kImgWidthHeight = 128;
     static const int kPad = 4;

     sk_sp<SkImage> fETC1Image;
     sk_sp<SkImage> fBC1Image;

     typedef GM INHERITED;
 };

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

 DEF_GM(return new ExoticFormatsGM;)
 }
	/*
	* Copyright 2020 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "gm/gm.h"
	#include "include/core/SkCanvas.h"
	#include "include/core/SkImage.h"
	#include "include/core/SkStream.h"
	#include "src/core/SkCompressedDataUtils.h"
	#include "src/core/SkMipMap.h"
	#include "src/gpu/GrContextPriv.h"
	#include "src/gpu/gl/GrGLDefines.h"
	#include "src/image/SkImage_Base.h"

	#include "tools/Resources.h"

	//-------------------------------------------------------------------------------------------------
	struct ImageInfo {
	SkISize fDim;
	GrMipMapped fMipMapped;
	SkImage::CompressionType fCompressionType;
	};

	/*
	* Get an int from a buffer
	* This method is unsafe, the caller is responsible for performing a check
	*/
	static inline uint32_t get_uint(uint8_t* buffer, uint32_t i) {
	uint32_t result;
	memcpy(&result, &(buffer[i]), 4);
	return result;
	}

	// This KTX loader is barely sufficient to load the specific files this GM requires. Use
	// at your own peril.
	static sk_sp<SkData> load_ktx(const char* filename, ImageInfo* imageInfo) {
	SkFILEStream input(filename);
	if (!input.isValid()) {
	return nullptr;
	}

	constexpr int kKTXIdentifierSize = 12;
	constexpr int kKTXHeaderSize = kKTXIdentifierSize + 13 * sizeof(uint32_t);
	uint8_t header[kKTXHeaderSize];

	if (input.read(header, kKTXHeaderSize) != kKTXHeaderSize) {
	return nullptr;
	}

	static const uint8_t kExpectedIdentifier[kKTXIdentifierSize] = {
	0xAB, 0x4B, 0x54, 0x58, 0x20, 0x31, 0x31, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A
	};

	if (memcmp(header, kExpectedIdentifier, kKTXIdentifierSize)) {
	return nullptr;
	}

	uint32_t endianness = get_uint(header, 12);
	if (endianness != 0x04030201) {
	// TODO: need to swap rest of header and, if glTypeSize is > 1, all
	// the texture data.
	return nullptr;
	}

	uint32_t glType = get_uint(header, 16);
	SkDEBUGCODE(uint32_t glTypeSize = get_uint(header, 20);)
	uint32_t glFormat = get_uint(header, 24);
	uint32_t glInternalFormat = get_uint(header, 28);
	//uint32_t glBaseInternalFormat = get_uint(header, 32);
	uint32_t pixelWidth = get_uint(header, 36);
	uint32_t pixelHeight = get_uint(header, 40);
	uint32_t pixelDepth = get_uint(header, 44);
	//uint32_t numberOfArrayElements = get_uint(header, 48);
	uint32_t numberOfFaces = get_uint(header, 52);
	int numberOfMipmapLevels = get_uint(header, 56);
	uint32_t bytesOfKeyValueData = get_uint(header, 60);

	if (glType != 0 \|\| glFormat != 0) { // only care about compressed data for now
	return nullptr;
	}
	SkASSERT(glTypeSize == 1); // required for compressed data

	// We only handle these four formats right now
	switch (glInternalFormat) {
	case GR_GL_COMPRESSED_ETC1_RGB8:
	case GR_GL_COMPRESSED_RGB8_ETC2:
	imageInfo->fCompressionType = SkImage::CompressionType::kETC2_RGB8_UNORM;
	break;
	case GR_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
	imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGB8_UNORM;
	break;
	case GR_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
	imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGBA8_UNORM;
	break;
	default:
	return nullptr;
	}

	imageInfo->fDim.fWidth = pixelWidth;
	imageInfo->fDim.fHeight = pixelHeight;

	if (pixelDepth != 0) {
	return nullptr; // pixel depth is always zero for 2D textures
	}

	if (numberOfFaces != 1) {
	return nullptr; // we don't support cube maps right now
	}

	if (numberOfMipmapLevels == 1) {
	imageInfo->fMipMapped = GrMipMapped::kNo;
	} else {
	int numRequiredMipLevels = SkMipMap::ComputeLevelCount(pixelWidth, pixelHeight)+1;
	if (numberOfMipmapLevels != numRequiredMipLevels) {
	return nullptr;
	}
	imageInfo->fMipMapped = GrMipMapped::kYes;
	}

	if (bytesOfKeyValueData != 0) {
	return nullptr;
	}

	SkTArray<size_t> individualMipOffsets(numberOfMipmapLevels);

	size_t dataSize = SkCompressedDataSize(imageInfo->fCompressionType,
	{ (int) pixelWidth, (int) pixelHeight },
	&individualMipOffsets,
	imageInfo->fMipMapped == GrMipMapped::kYes);
	SkASSERT(individualMipOffsets.size() == (size_t) numberOfMipmapLevels);

	sk_sp<SkData> data = SkData::MakeUninitialized(dataSize);

	uint8_t* dest = (uint8_t*) data->writable_data();

	size_t offset = 0;
	for (int i = 0; i < numberOfMipmapLevels; ++i) {
	uint32_t imageSize;

	if (input.read(&imageSize, 4) != 4) {
	return nullptr;
	}

	SkASSERT(offset + imageSize <= dataSize);
	SkASSERT(offset == individualMipOffsets[i]);

	if (input.read(&dest[offset], imageSize) != imageSize) {
	return nullptr;
	}

	offset += imageSize;
	}

	return data;
	}

	//-------------------------------------------------------------------------------------------------
	typedef uint32_t DWORD;

	// Values for the DDS_PIXELFORMAT 'dwFlags' field
	constexpr unsigned int kDDPF_FOURCC = 0x4;

	struct DDS_PIXELFORMAT {
	DWORD dwSize;
	DWORD dwFlags;
	DWORD dwFourCC;
	DWORD dwRGBBitCount;
	DWORD dwRBitMask;
	DWORD dwGBitMask;
	DWORD dwBBitMask;
	DWORD dwABitMask;
	};

	// Values for the DDS_HEADER 'dwFlags' field
	constexpr unsigned int kDDSD_CAPS = 0x1; // required
	constexpr unsigned int kDDSD_HEIGHT = 0x2; // required
	constexpr unsigned int kDDSD_WIDTH = 0x4; // required
	constexpr unsigned int kDDSD_PITCH = 0x8;
	constexpr unsigned int kDDSD_PIXELFORMAT = 0x001000; // required
	constexpr unsigned int kDDSD_MIPMAPCOUNT = 0x020000;
	constexpr unsigned int kDDSD_LINEARSIZE = 0x080000;
	constexpr unsigned int kDDSD_DEPTH = 0x800000;

	constexpr unsigned int kDDSD_REQUIRED = kDDSD_CAPS \| kDDSD_HEIGHT \| kDDSD_WIDTH \| kDDSD_PIXELFORMAT;

	typedef struct {
	DWORD dwSize;
	DWORD dwFlags;
	DWORD dwHeight;
	DWORD dwWidth;
	DWORD dwPitchOrLinearSize;
	DWORD dwDepth;
	DWORD dwMipMapCount;
	DWORD dwReserved1[11];
	DDS_PIXELFORMAT ddspf;
	DWORD dwCaps;
	DWORD dwCaps2;
	DWORD dwCaps3;
	DWORD dwCaps4;
	DWORD dwReserved2;
	} DDS_HEADER;

	// This DDS loader is barely sufficient to load the specific files this GM requires. Use
	// at your own peril.
	static sk_sp<SkData> load_dds(const char* filename, ImageInfo* imageInfo) {
	SkFILEStream input(filename);
	if (!input.isValid()) {
	return nullptr;
	}

	constexpr uint32_t kMagic = 0x20534444;
	uint32_t magic;

	if (input.read(&magic, 4) != 4) {
	return nullptr;
	}

	if (magic != kMagic) {
	return nullptr;
	}

	constexpr size_t kDDSHeaderSize = sizeof(DDS_HEADER);
	static_assert(kDDSHeaderSize == 124);
	constexpr size_t kDDSPixelFormatSize = sizeof(DDS_PIXELFORMAT);
	static_assert(kDDSPixelFormatSize == 32);

	DDS_HEADER header;

	if (input.read(&header, kDDSHeaderSize) != kDDSHeaderSize) {
	return nullptr;
	}

	if (header.dwSize != kDDSHeaderSize \|\|
	header.ddspf.dwSize != kDDSPixelFormatSize) {
	return nullptr;
	}

	if ((header.dwFlags & kDDSD_REQUIRED) != kDDSD_REQUIRED) {
	return nullptr;
	}

	if (header.dwFlags & (kDDSD_PITCH \| kDDSD_LINEARSIZE \| kDDSD_DEPTH)) {
	// TODO: support these features
	}

	imageInfo->fDim.fWidth = header.dwWidth;
	imageInfo->fDim.fHeight = header.dwHeight;

	int numberOfMipmapLevels = 1;
	if (header.dwFlags & kDDSD_MIPMAPCOUNT) {
	if (header.dwMipMapCount == 1) {
	imageInfo->fMipMapped = GrMipMapped::kNo;
	} else {
	int numRequiredLevels = SkMipMap::ComputeLevelCount(header.dwWidth, header.dwHeight)+1;
	if (header.dwMipMapCount != (unsigned) numRequiredLevels) {
	return nullptr;
	}
	imageInfo->fMipMapped = GrMipMapped::kYes;
	numberOfMipmapLevels = numRequiredLevels;
	}
	} else {
	imageInfo->fMipMapped = GrMipMapped::kNo;
	}

	if (!(header.ddspf.dwFlags & kDDPF_FOURCC)) {
	return nullptr;
	}

	// We only handle these one format right now
	switch (header.ddspf.dwFourCC) {
	case 0x31545844: // DXT1
	imageInfo->fCompressionType = SkImage::CompressionType::kBC1_RGB8_UNORM;
	break;
	default:
	return nullptr;
	}

	SkTArray<size_t> individualMipOffsets(numberOfMipmapLevels);

	size_t dataSize = SkCompressedDataSize(imageInfo->fCompressionType,
	{ (int) header.dwWidth, (int) header.dwHeight },
	&individualMipOffsets,
	imageInfo->fMipMapped == GrMipMapped::kYes);
	SkASSERT(individualMipOffsets.size() == (size_t) numberOfMipmapLevels);

	sk_sp<SkData> data = SkData::MakeUninitialized(dataSize);

	uint8_t* dest = (uint8_t*) data->writable_data();

	size_t amountRead = input.read(dest, dataSize);
	if (amountRead != dataSize) {
	return nullptr;
	}

	return data;
	}

	//-------------------------------------------------------------------------------------------------
	static sk_sp<SkImage> data_to_img(GrContext *context, sk_sp<SkData> data, const ImageInfo& info) {
	if (context) {
	return SkImage::MakeTextureFromCompressed(context, std::move(data),
	info.fDim.fWidth,
	info.fDim.fHeight,
	info.fCompressionType,
	info.fMipMapped);
	} else {
	return SkImage::MakeRasterFromCompressed(std::move(data),
	info.fDim.fWidth,
	info.fDim.fHeight,
	info.fCompressionType);
	}
	}

	namespace skiagm {

	// This GM exercises our handling of some of the more exotic formats using externally
	// generated content. Right now it only tests ETC1 and BC1.
	class ExoticFormatsGM : public GM {
	public:
	ExoticFormatsGM() {
	this->setBGColor(SK_ColorBLACK);
	}

	protected:
	SkString onShortName() override {
	return SkString("exoticformats");
	}

	SkISize onISize() override {
	return SkISize::Make(2kImgWidthHeight + 3 kPad, kImgWidthHeight + 2 * kPad);
	}

	void loadImages(GrContext *context) {

	if (!fETC1Image) {
	ImageInfo info;
	sk_sp<SkData> data = load_ktx(GetResourcePath("images/flower-etc1.ktx").c_str(), &info);
	if (data) {
	SkASSERT(info.fDim.equals(kImgWidthHeight, kImgWidthHeight));
	SkASSERT(info.fMipMapped == GrMipMapped::kNo);
	SkASSERT(info.fCompressionType == SkImage::CompressionType::kETC2_RGB8_UNORM);

	fETC1Image = data_to_img(context, std::move(data), info);
	} else {
	SkDebugf("failed to load flower-etc1.ktx\n");
	}
	}

	if (!fBC1Image) {
	ImageInfo info;
	sk_sp<SkData> data = load_dds(GetResourcePath("images/flower-bc1.dds").c_str(), &info);
	if (data) {
	SkASSERT(info.fDim.equals(kImgWidthHeight, kImgWidthHeight));
	SkASSERT(info.fMipMapped == GrMipMapped::kNo);
	SkASSERT(info.fCompressionType == SkImage::CompressionType::kBC1_RGB8_UNORM);

	fBC1Image = data_to_img(context, std::move(data), info);
	} else {
	SkDebugf("failed to load flower-bc1.dds\n");
	}
	}

	}

	void drawImage(GrContext* context, SkCanvas* canvas, SkImage* image, int x, int y) {
	if (!image) {
	return;
	}

	bool isCompressed = false;
	if (image->isTextureBacked()) {
	const GrCaps* caps = context->priv().caps();

	GrTextureProxy* proxy = as_IB(image)->peekProxy();
	isCompressed = caps->isFormatCompressed(proxy->backendFormat());
	}

	canvas->drawImage(image, x, y);

	if (!isCompressed) {
	// Make it obvious which drawImages used decompressed images
	SkRect r = SkRect::MakeXYWH(x, y, kImgWidthHeight, kImgWidthHeight);
	SkPaint paint;
	paint.setColor(SK_ColorRED);
	paint.setStyle(SkPaint::kStroke_Style);
	paint.setStrokeWidth(2.0f);
	canvas->drawRect(r, paint);
	}
	}

	void onDraw(SkCanvas* canvas) override {
	GrContext* context = canvas->getGrContext();

	this->loadImages(context);

	this->drawImage(context, canvas, fETC1Image.get(), kPad, kPad);
	this->drawImage(context, canvas, fBC1Image.get(), kImgWidthHeight + 2 * kPad, kPad);
	}

	private:
	static const int kImgWidthHeight = 128;
	static const int kPad = 4;

	sk_sp<SkImage> fETC1Image;
	sk_sp<SkImage> fBC1Image;

	typedef GM INHERITED;
	};

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

	DEF_GM(return new ExoticFormatsGM;)
	}