base/gfx/png_decoder.cc - chromium/src - Git at Google

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "base/gfx/png_decoder.h"

 #include "base/logging.h"
 #include "third_party/skia/include/core/SkBitmap.h"

 extern "C" {
 #include "third_party/libpng/png.h"
 }

 namespace {

 // Converts BGRA->RGBA and RGBA->BGRA.
 void ConvertBetweenBGRAandRGBA(const unsigned char* input, int pixel_width,
                                unsigned char* output) {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &input[x * 4];
     unsigned char* pixel_out = &output[x * 4];
     pixel_out[0] = pixel_in[2];
     pixel_out[1] = pixel_in[1];
     pixel_out[2] = pixel_in[0];
     pixel_out[3] = pixel_in[3];
   }
 }

 void ConvertRGBAtoRGB(const unsigned char* rgba, int pixel_width,
                       unsigned char* rgb) {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &rgba[x * 4];
     unsigned char* pixel_out = &rgb[x * 3];
     pixel_out[0] = pixel_in[0];
     pixel_out[1] = pixel_in[1];
     pixel_out[2] = pixel_in[2];
   }
 }

 }  // namespace

 // Decoder --------------------------------------------------------------------
 //
 // This code is based on WebKit libpng interface (PNGImageDecoder), which is
 // in turn based on the Mozilla png decoder.

 namespace {

 // Gamma constants: We assume we're on Windows which uses a gamma of 2.2.
 const double kMaxGamma = 21474.83;  // Maximum gamma accepted by png library.
 const double kDefaultGamma = 2.2;
 const double kInverseGamma = 1.0 / kDefaultGamma;

 class PngDecoderState {
  public:
   PngDecoderState(PNGDecoder::ColorFormat ofmt, std::vector<unsigned char>* o)
       : output_format(ofmt),
         output_channels(0),
         output(o),
         row_converter(NULL),
         width(0),
         height(0),
         done(false) {
   }

   PNGDecoder::ColorFormat output_format;
   int output_channels;

   std::vector<unsigned char>* output;

   // Called to convert a row from the library to the correct output format.
   // When NULL, no conversion is necessary.
   void (*row_converter)(const unsigned char* in, int w, unsigned char* out);

   // Size of the image, set in the info callback.
   int width;
   int height;

   // Set to true when we've found the end of the data.
   bool done;

  private:
   DISALLOW_EVIL_CONSTRUCTORS(PngDecoderState);
 };

 void ConvertRGBtoRGBA(const unsigned char* rgb, int pixel_width,
                       unsigned char* rgba) {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &rgb[x * 3];
     unsigned char* pixel_out = &rgba[x * 4];
     pixel_out[0] = pixel_in[0];
     pixel_out[1] = pixel_in[1];
     pixel_out[2] = pixel_in[2];
     pixel_out[3] = 0xff;
   }
 }

 void ConvertRGBtoBGRA(const unsigned char* rgb, int pixel_width,
                       unsigned char* bgra) {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &rgb[x * 3];
     unsigned char* pixel_out = &bgra[x * 4];
     pixel_out[0] = pixel_in[2];
     pixel_out[1] = pixel_in[1];
     pixel_out[2] = pixel_in[0];
     pixel_out[3] = 0xff;
   }
 }

 // Called when the png header has been read. This code is based on the WebKit
 // PNGImageDecoder
 void DecodeInfoCallback(png_struct* png_ptr, png_info* info_ptr) {
   PngDecoderState* state = static_cast<PngDecoderState*>(
       png_get_progressive_ptr(png_ptr));

   int bit_depth, color_type, interlace_type, compression_type;
   int filter_type, channels;
   png_uint_32 w, h;
   png_get_IHDR(png_ptr, info_ptr, &w, &h, &bit_depth, &color_type,
                &interlace_type, &compression_type, &filter_type);

   // Bounds check. When the image is unreasonably big, we'll error out and
   // end up back at the setjmp call when we set up decoding.  "Unreasonably big"
   // means "big enough that w * h * 32bpp might overflow an int"; we choose this
   // threshold to match WebKit and because a number of places in code assume
   // that an image's size (in bytes) fits in a (signed) int.
   unsigned long long total_size =
       static_cast<unsigned long long>(w) * static_cast<unsigned long long>(h);
   if (total_size > ((1 << 29) - 1))
     longjmp(png_ptr->jmpbuf, 1);
   state->width = static_cast<int>(w);
   state->height = static_cast<int>(h);

   // Expand to ensure we use 24-bit for RGB and 32-bit for RGBA.
   if (color_type == PNG_COLOR_TYPE_PALETTE ||
       (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8))
     png_set_expand(png_ptr);

   // Transparency for paletted images.
   if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
     png_set_expand(png_ptr);

   // Convert 16-bit to 8-bit.
   if (bit_depth == 16)
     png_set_strip_16(png_ptr);

   // Expand grayscale to RGB.
   if (color_type == PNG_COLOR_TYPE_GRAY ||
       color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
     png_set_gray_to_rgb(png_ptr);

   // Deal with gamma and keep it under our control.
   double gamma;
   if (png_get_gAMA(png_ptr, info_ptr, &gamma)) {
     if (gamma <= 0.0 || gamma > kMaxGamma) {
       gamma = kInverseGamma;
       png_set_gAMA(png_ptr, info_ptr, gamma);
     }
     png_set_gamma(png_ptr, kDefaultGamma, gamma);
   } else {
     png_set_gamma(png_ptr, kDefaultGamma, kInverseGamma);
   }

   // Tell libpng to send us rows for interlaced pngs.
   if (interlace_type == PNG_INTERLACE_ADAM7)
     png_set_interlace_handling(png_ptr);

   // Update our info now
   png_read_update_info(png_ptr, info_ptr);
   channels = png_get_channels(png_ptr, info_ptr);

   // Pick our row format converter necessary for this data.
   if (channels == 3) {
     switch (state->output_format) {
       case PNGDecoder::FORMAT_RGB:
         state->row_converter = NULL;  // no conversion necessary
         state->output_channels = 3;
         break;
       case PNGDecoder::FORMAT_RGBA:
         state->row_converter = &ConvertRGBtoRGBA;
         state->output_channels = 4;
         break;
       case PNGDecoder::FORMAT_BGRA:
         state->row_converter = &ConvertRGBtoBGRA;
         state->output_channels = 4;
         break;
       default:
         NOTREACHED() << "Unknown output format";
         break;
     }
   } else if (channels == 4) {
     switch (state->output_format) {
       case PNGDecoder::FORMAT_RGB:
         state->row_converter = &ConvertRGBAtoRGB;
         state->output_channels = 3;
         break;
       case PNGDecoder::FORMAT_RGBA:
         state->row_converter = NULL;  // no conversion necessary
         state->output_channels = 4;
         break;
       case PNGDecoder::FORMAT_BGRA:
         state->row_converter = &ConvertBetweenBGRAandRGBA;
         state->output_channels = 4;
         break;
       default:
         NOTREACHED() << "Unknown output format";
         break;
     }
   } else {
     NOTREACHED() << "Unknown input channels";
     longjmp(png_ptr->jmpbuf, 1);
   }

   state->output->resize(state->width * state->output_channels * state->height);
 }

 void DecodeRowCallback(png_struct* png_ptr, png_byte* new_row,
                        png_uint_32 row_num, int pass) {
   PngDecoderState* state = static_cast<PngDecoderState*>(
       png_get_progressive_ptr(png_ptr));

   DCHECK(pass == 0) << "We didn't turn on interlace handling, but libpng is "
                        "giving us interlaced data.";
   if (static_cast<int>(row_num) > state->height) {
     NOTREACHED() << "Invalid row";
     return;
   }

   unsigned char* dest = &(*state->output)[
       state->width * state->output_channels * row_num];
   if (state->row_converter)
     state->row_converter(new_row, state->width, dest);
   else
     memcpy(dest, new_row, state->width * state->output_channels);
 }

 void DecodeEndCallback(png_struct* png_ptr, png_info* info) {
   PngDecoderState* state = static_cast<PngDecoderState*>(
       png_get_progressive_ptr(png_ptr));

   // Mark the image as complete, this will tell the Decode function that we
   // have successfully found the end of the data.
   state->done = true;
 }

 // Automatically destroys the given read structs on destruction to make
 // cleanup and error handling code cleaner.
 class PngReadStructDestroyer {
  public:
   PngReadStructDestroyer(png_struct** ps, png_info** pi) : ps_(ps), pi_(pi) {
   }
   ~PngReadStructDestroyer() {
     png_destroy_read_struct(ps_, pi_, NULL);
   }
  private:
   png_struct** ps_;
   png_info** pi_;
 };

 }  // namespace

 // static
 bool PNGDecoder::Decode(const unsigned char* input, size_t input_size,
                       ColorFormat format, std::vector<unsigned char>* output,
                       int* w, int* h) {
   if (input_size < 8)
     return false;  // Input data too small to be a png

   // Have libpng check the signature, it likes the first 8 bytes.
   if (png_sig_cmp(const_cast<unsigned char*>(input), 0, 8) != 0)
     return false;

   png_struct* png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
                                                png_voidp_NULL,
                                                png_error_ptr_NULL,
                                                png_error_ptr_NULL);
   if (!png_ptr)
     return false;

   png_info* info_ptr = png_create_info_struct(png_ptr);
   if (!info_ptr) {
     png_destroy_read_struct(&png_ptr, NULL, NULL);
     return false;
   }

   PngReadStructDestroyer destroyer(&png_ptr, &info_ptr);
   if (setjmp(png_jmpbuf(png_ptr))) {
     // The destroyer will ensure that the structures are cleaned up in this
     // case, even though we may get here as a jump from random parts of the
     // PNG library called below.
     return false;
   }

   PngDecoderState state(format, output);

   png_set_progressive_read_fn(png_ptr, &state, &DecodeInfoCallback,
                               &DecodeRowCallback, &DecodeEndCallback);
   png_process_data(png_ptr,
                    info_ptr,
                    const_cast<unsigned char*>(input),
                    input_size);

   if (!state.done) {
     // Fed it all the data but the library didn't think we got all the data, so
     // this file must be truncated.
     output->clear();
     return false;
   }

   *w = state.width;
   *h = state.height;
   return true;
 }

 // static
 bool PNGDecoder::Decode(const std::vector<unsigned char>* data,
                         SkBitmap* bitmap) {
   DCHECK(bitmap);
   if (!data || data->empty())
     return false;
   int width, height;
   std::vector<unsigned char> decoded_data;
   if (PNGDecoder::Decode(&data->front(), data->size(), PNGDecoder::FORMAT_BGRA,
                          &decoded_data, &width, &height)) {
     bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
     bitmap->allocPixels();
     memcpy(bitmap->getPixels(), &decoded_data.front(), width * height * 4);
     return true;
   }
   return false;
 }

 //static
 SkBitmap* PNGDecoder::CreateSkBitmapFromBGRAFormat(
     std::vector<unsigned char>& bgra, int width, int height) {
   SkBitmap* bitmap = new SkBitmap();
   bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
   bitmap->allocPixels();

   bool opaque = false;
   unsigned char* bitmap_data =
       reinterpret_cast<unsigned char*>(bitmap->getAddr32(0, 0));
   for (int i = width * height * 4 - 4; i >= 0; i -= 4) {
     unsigned char alpha = bgra[i + 3];
     if (!opaque && alpha != 255) {
       opaque = false;
     }
     bitmap_data[i + 3] = alpha;
     bitmap_data[i] = (bgra[i] * alpha) >> 8;
     bitmap_data[i + 1] = (bgra[i + 1] * alpha) >> 8;
     bitmap_data[i + 2] = (bgra[i + 2] * alpha) >> 8;
   }

   bitmap->setIsOpaque(opaque);
   return bitmap;
 }
	// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "base/gfx/png_decoder.h"

	#include "base/logging.h"
	#include "third_party/skia/include/core/SkBitmap.h"

	extern "C" {
	#include "third_party/libpng/png.h"
	}

	namespace {

	// Converts BGRA->RGBA and RGBA->BGRA.
	void ConvertBetweenBGRAandRGBA(const unsigned char* input, int pixel_width,
	unsigned char* output) {
	for (int x = 0; x < pixel_width; x++) {
	const unsigned char* pixel_in = &input[x * 4];
	unsigned char* pixel_out = &output[x * 4];
	pixel_out[0] = pixel_in[2];
	pixel_out[1] = pixel_in[1];
	pixel_out[2] = pixel_in[0];
	pixel_out[3] = pixel_in[3];
	}
	}

	void ConvertRGBAtoRGB(const unsigned char* rgba, int pixel_width,
	unsigned char* rgb) {
	for (int x = 0; x < pixel_width; x++) {
	const unsigned char* pixel_in = &rgba[x * 4];
	unsigned char* pixel_out = &rgb[x * 3];
	pixel_out[0] = pixel_in[0];
	pixel_out[1] = pixel_in[1];
	pixel_out[2] = pixel_in[2];
	}
	}

	} // namespace

	// Decoder --------------------------------------------------------------------
	//
	// This code is based on WebKit libpng interface (PNGImageDecoder), which is
	// in turn based on the Mozilla png decoder.

	namespace {

	// Gamma constants: We assume we're on Windows which uses a gamma of 2.2.
	const double kMaxGamma = 21474.83; // Maximum gamma accepted by png library.
	const double kDefaultGamma = 2.2;
	const double kInverseGamma = 1.0 / kDefaultGamma;

	class PngDecoderState {
	public:
	PngDecoderState(PNGDecoder::ColorFormat ofmt, std::vector<unsigned char>* o)
	: output_format(ofmt),
	output_channels(0),
	output(o),
	row_converter(NULL),
	width(0),
	height(0),
	done(false) {
	}

	PNGDecoder::ColorFormat output_format;
	int output_channels;

	std::vector<unsigned char>* output;

	// Called to convert a row from the library to the correct output format.
	// When NULL, no conversion is necessary.
	void (row_converter)(const unsigned char in, int w, unsigned char* out);

	// Size of the image, set in the info callback.
	int width;
	int height;

	// Set to true when we've found the end of the data.
	bool done;

	private:
	DISALLOW_EVIL_CONSTRUCTORS(PngDecoderState);
	};

	void ConvertRGBtoRGBA(const unsigned char* rgb, int pixel_width,
	unsigned char* rgba) {
	for (int x = 0; x < pixel_width; x++) {
	const unsigned char* pixel_in = &rgb[x * 3];
	unsigned char* pixel_out = &rgba[x * 4];
	pixel_out[0] = pixel_in[0];
	pixel_out[1] = pixel_in[1];
	pixel_out[2] = pixel_in[2];
	pixel_out[3] = 0xff;
	}
	}

	void ConvertRGBtoBGRA(const unsigned char* rgb, int pixel_width,
	unsigned char* bgra) {
	for (int x = 0; x < pixel_width; x++) {
	const unsigned char* pixel_in = &rgb[x * 3];
	unsigned char* pixel_out = &bgra[x * 4];
	pixel_out[0] = pixel_in[2];
	pixel_out[1] = pixel_in[1];
	pixel_out[2] = pixel_in[0];
	pixel_out[3] = 0xff;
	}
	}

	// Called when the png header has been read. This code is based on the WebKit
	// PNGImageDecoder
	void DecodeInfoCallback(png_struct* png_ptr, png_info* info_ptr) {
	PngDecoderState* state = static_cast<PngDecoderState*>(
	png_get_progressive_ptr(png_ptr));

	int bit_depth, color_type, interlace_type, compression_type;
	int filter_type, channels;
	png_uint_32 w, h;
	png_get_IHDR(png_ptr, info_ptr, &w, &h, &bit_depth, &color_type,
	&interlace_type, &compression_type, &filter_type);

	// Bounds check. When the image is unreasonably big, we'll error out and
	// end up back at the setjmp call when we set up decoding. "Unreasonably big"
	// means "big enough that w * h * 32bpp might overflow an int"; we choose this
	// threshold to match WebKit and because a number of places in code assume
	// that an image's size (in bytes) fits in a (signed) int.
	unsigned long long total_size =
	static_cast<unsigned long long>(w) * static_cast<unsigned long long>(h);
	if (total_size > ((1 << 29) - 1))
	longjmp(png_ptr->jmpbuf, 1);
	state->width = static_cast<int>(w);
	state->height = static_cast<int>(h);

	// Expand to ensure we use 24-bit for RGB and 32-bit for RGBA.
	if (color_type == PNG_COLOR_TYPE_PALETTE \|\|
	(color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8))
	png_set_expand(png_ptr);

	// Transparency for paletted images.
	if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
	png_set_expand(png_ptr);

	// Convert 16-bit to 8-bit.
	if (bit_depth == 16)
	png_set_strip_16(png_ptr);

	// Expand grayscale to RGB.
	if (color_type == PNG_COLOR_TYPE_GRAY \|\|
	color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
	png_set_gray_to_rgb(png_ptr);

	// Deal with gamma and keep it under our control.
	double gamma;
	if (png_get_gAMA(png_ptr, info_ptr, &gamma)) {
	if (gamma <= 0.0 \|\| gamma > kMaxGamma) {
	gamma = kInverseGamma;
	png_set_gAMA(png_ptr, info_ptr, gamma);
	}
	png_set_gamma(png_ptr, kDefaultGamma, gamma);
	} else {
	png_set_gamma(png_ptr, kDefaultGamma, kInverseGamma);
	}

	// Tell libpng to send us rows for interlaced pngs.
	if (interlace_type == PNG_INTERLACE_ADAM7)
	png_set_interlace_handling(png_ptr);

	// Update our info now
	png_read_update_info(png_ptr, info_ptr);
	channels = png_get_channels(png_ptr, info_ptr);

	// Pick our row format converter necessary for this data.
	if (channels == 3) {
	switch (state->output_format) {
	case PNGDecoder::FORMAT_RGB:
	state->row_converter = NULL; // no conversion necessary
	state->output_channels = 3;
	break;
	case PNGDecoder::FORMAT_RGBA:
	state->row_converter = &ConvertRGBtoRGBA;
	state->output_channels = 4;
	break;
	case PNGDecoder::FORMAT_BGRA:
	state->row_converter = &ConvertRGBtoBGRA;
	state->output_channels = 4;
	break;
	default:
	NOTREACHED() << "Unknown output format";
	break;
	}
	} else if (channels == 4) {
	switch (state->output_format) {
	case PNGDecoder::FORMAT_RGB:
	state->row_converter = &ConvertRGBAtoRGB;
	state->output_channels = 3;
	break;
	case PNGDecoder::FORMAT_RGBA:
	state->row_converter = NULL; // no conversion necessary
	state->output_channels = 4;
	break;
	case PNGDecoder::FORMAT_BGRA:
	state->row_converter = &ConvertBetweenBGRAandRGBA;
	state->output_channels = 4;
	break;
	default:
	NOTREACHED() << "Unknown output format";
	break;
	}
	} else {
	NOTREACHED() << "Unknown input channels";
	longjmp(png_ptr->jmpbuf, 1);
	}

	state->output->resize(state->width * state->output_channels * state->height);
	}

	void DecodeRowCallback(png_struct* png_ptr, png_byte* new_row,
	png_uint_32 row_num, int pass) {
	PngDecoderState* state = static_cast<PngDecoderState*>(
	png_get_progressive_ptr(png_ptr));

	DCHECK(pass == 0) << "We didn't turn on interlace handling, but libpng is "
	"giving us interlaced data.";
	if (static_cast<int>(row_num) > state->height) {
	NOTREACHED() << "Invalid row";
	return;
	}

	unsigned char* dest = &(*state->output)[
	state->width * state->output_channels * row_num];
	if (state->row_converter)
	state->row_converter(new_row, state->width, dest);
	else
	memcpy(dest, new_row, state->width * state->output_channels);
	}

	void DecodeEndCallback(png_struct* png_ptr, png_info* info) {
	PngDecoderState* state = static_cast<PngDecoderState*>(
	png_get_progressive_ptr(png_ptr));

	// Mark the image as complete, this will tell the Decode function that we
	// have successfully found the end of the data.
	state->done = true;
	}

	// Automatically destroys the given read structs on destruction to make
	// cleanup and error handling code cleaner.
	class PngReadStructDestroyer {
	public:
	PngReadStructDestroyer(png_struct ps, png_info pi) : ps_(ps), pi_(pi) {
	}
	~PngReadStructDestroyer() {
	png_destroy_read_struct(ps_, pi_, NULL);
	}
	private:
	png_struct** ps_;
	png_info** pi_;
	};

	} // namespace

	// static
	bool PNGDecoder::Decode(const unsigned char* input, size_t input_size,
	ColorFormat format, std::vector<unsigned char>* output,
	int* w, int* h) {
	if (input_size < 8)
	return false; // Input data too small to be a png

	// Have libpng check the signature, it likes the first 8 bytes.
	if (png_sig_cmp(const_cast<unsigned char*>(input), 0, 8) != 0)
	return false;

	png_struct* png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
	png_voidp_NULL,
	png_error_ptr_NULL,
	png_error_ptr_NULL);
	if (!png_ptr)
	return false;

	png_info* info_ptr = png_create_info_struct(png_ptr);
	if (!info_ptr) {
	png_destroy_read_struct(&png_ptr, NULL, NULL);
	return false;
	}

	PngReadStructDestroyer destroyer(&png_ptr, &info_ptr);
	if (setjmp(png_jmpbuf(png_ptr))) {
	// The destroyer will ensure that the structures are cleaned up in this
	// case, even though we may get here as a jump from random parts of the
	// PNG library called below.
	return false;
	}

	PngDecoderState state(format, output);

	png_set_progressive_read_fn(png_ptr, &state, &DecodeInfoCallback,
	&DecodeRowCallback, &DecodeEndCallback);
	png_process_data(png_ptr,
	info_ptr,
	const_cast<unsigned char*>(input),
	input_size);

	if (!state.done) {
	// Fed it all the data but the library didn't think we got all the data, so
	// this file must be truncated.
	output->clear();
	return false;
	}

	*w = state.width;
	*h = state.height;
	return true;
	}

	// static
	bool PNGDecoder::Decode(const std::vector<unsigned char>* data,
	SkBitmap* bitmap) {
	DCHECK(bitmap);
	if (!data \|\| data->empty())
	return false;
	int width, height;
	std::vector<unsigned char> decoded_data;
	if (PNGDecoder::Decode(&data->front(), data->size(), PNGDecoder::FORMAT_BGRA,
	&decoded_data, &width, &height)) {
	bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
	bitmap->allocPixels();
	memcpy(bitmap->getPixels(), &decoded_data.front(), width * height * 4);
	return true;
	}
	return false;
	}

	//static
	SkBitmap* PNGDecoder::CreateSkBitmapFromBGRAFormat(
	std::vector<unsigned char>& bgra, int width, int height) {
	SkBitmap* bitmap = new SkBitmap();
	bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
	bitmap->allocPixels();

	bool opaque = false;
	unsigned char* bitmap_data =
	reinterpret_cast<unsigned char*>(bitmap->getAddr32(0, 0));
	for (int i = width * height * 4 - 4; i >= 0; i -= 4) {
	unsigned char alpha = bgra[i + 3];
	if (!opaque && alpha != 255) {
	opaque = false;
	}
	bitmap_data[i + 3] = alpha;
	bitmap_data[i] = (bgra[i] * alpha) >> 8;
	bitmap_data[i + 1] = (bgra[i + 1] * alpha) >> 8;
	bitmap_data[i + 2] = (bgra[i + 2] * alpha) >> 8;
	}

	bitmap->setIsOpaque(opaque);
	return bitmap;
	}