C++ png_set_expand函数代码示例

bool PNGDecoder::loadStream(Common::SeekableReadStream &stream) {
#ifdef USE_PNG
	destroy();

	_stream = &stream;

	// First, check the PNG signature
	if (_stream->readUint32BE() != MKTAG(0x89, 'P', 'N', 'G')) {
		delete _stream;
		return false;
	}
	if (_stream->readUint32BE() != MKTAG(0x0d, 0x0a, 0x1a, 0x0a)) {
		delete _stream;
		return false;
	}

	// The following is based on the guide provided in:
	//http://www.libpng.org/pub/png/libpng-1.2.5-manual.html#section-3
	//http://www.libpng.org/pub/png/libpng-1.4.0-manual.pdf
	// along with the png-loading code used in the sword25-engine.
	png_structp pngPtr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	if (!pngPtr) {
		delete _stream;
		return false;
	}
	png_infop infoPtr = png_create_info_struct(pngPtr);
	if (!infoPtr) {
		png_destroy_read_struct(&pngPtr, NULL, NULL);
		delete _stream;
		return false;
	}
	png_infop endInfo = png_create_info_struct(pngPtr);
	if (!endInfo) {
		png_destroy_read_struct(&pngPtr, &infoPtr, NULL);
		delete _stream;
		return false;
	}

	png_set_error_fn(pngPtr, NULL, pngError, pngWarning);
	// TODO: The manual says errors should be handled via setjmp

	png_set_read_fn(pngPtr, _stream, pngReadFromStream);
	png_set_crc_action(pngPtr, PNG_CRC_DEFAULT, PNG_CRC_WARN_USE);
	// We already verified the PNG-header
	png_set_sig_bytes(pngPtr, 8);

	// Read PNG header
	png_read_info(pngPtr, infoPtr);

	// No handling for unknown chunks yet.
	int bitDepth, colorType, width, height, interlaceType;
	png_uint_32 w, h;
	png_get_IHDR(pngPtr, infoPtr, &w, &h, &bitDepth, &colorType, &interlaceType, NULL, NULL);
	width = w;
	height = h;

	// Allocate memory for the final image data.
	// To keep memory framentation low this happens before allocating memory for temporary image data.
	_outputSurface = new Graphics::Surface();

	// Images of all color formats except PNG_COLOR_TYPE_PALETTE
	// will be transformed into ARGB images
	if (colorType == PNG_COLOR_TYPE_PALETTE && !png_get_valid(pngPtr, infoPtr, PNG_INFO_tRNS)) {
		int numPalette = 0;
		png_colorp palette = NULL;
		uint32 success = png_get_PLTE(pngPtr, infoPtr, &palette, &numPalette);
		if (success != PNG_INFO_PLTE) {
			png_destroy_read_struct(&pngPtr, &infoPtr, NULL);
			return false;
		}
		_paletteColorCount = numPalette;
		_palette = new byte[_paletteColorCount * 3];
		for (int i = 0; i < _paletteColorCount; i++) {
			_palette[(i * 3)] = palette[i].red;
			_palette[(i * 3) + 1] = palette[i].green;
			_palette[(i * 3) + 2] = palette[i].blue;

		}
		_outputSurface->create(width, height, Graphics::PixelFormat::createFormatCLUT8());
		png_set_packing(pngPtr);
	} else {
		bool isAlpha = (colorType & PNG_COLOR_MASK_ALPHA);
		if (png_get_valid(pngPtr, infoPtr, PNG_INFO_tRNS)) {
			isAlpha = true;
			png_set_expand(pngPtr);
		}
		_outputSurface->create(width, height, Graphics::PixelFormat(4,
		                       8, 8, 8, isAlpha ? 8 : 0, 24, 16, 8, 0));
		if (!_outputSurface->getPixels()) {
			error("Could not allocate memory for output image.");
		}
		if (bitDepth == 16)
			png_set_strip_16(pngPtr);
		if (bitDepth < 8)
			png_set_expand(pngPtr);
		if (colorType == PNG_COLOR_TYPE_GRAY ||
			colorType == PNG_COLOR_TYPE_GRAY_ALPHA)
			png_set_gray_to_rgb(pngPtr);

		// PNGs are Big-Endian:
//.........这里部分代码省略.........

void PNGAPI
png_read_png(png_structp png_ptr, png_infop info_ptr,
             int transforms,
             voidp params)
{
    int row;

#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
    /* invert the alpha channel from opacity to transparency */
    if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
        png_set_invert_alpha(png_ptr);
#endif

    /* The call to png_read_info() gives us all of the information from the
     * PNG file before the first IDAT (image data chunk).
     */
    png_read_info(png_ptr, info_ptr);

    if (info_ptr->height > PNG_UINT_32_MAX/sizeof(png_bytep))
        png_error(png_ptr,"Image is too high to process with png_read_png()");

    /* -------------- image transformations start here ------------------- */

#if defined(PNG_READ_16_TO_8_SUPPORTED)
    /* tell libpng to strip 16 bit/color files down to 8 bits/color */
    if (transforms & PNG_TRANSFORM_STRIP_16)
        png_set_strip_16(png_ptr);
#endif

#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
    /* Strip alpha bytes from the input data without combining with the
     * background (not recommended).
     */
    if (transforms & PNG_TRANSFORM_STRIP_ALPHA)
        png_set_strip_alpha(png_ptr);
#endif

#if defined(PNG_READ_PACK_SUPPORTED) && !defined(PNG_READ_EXPAND_SUPPORTED)
    /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
     * byte into separate bytes (useful for paletted and grayscale images).
     */
    if (transforms & PNG_TRANSFORM_PACKING)
        png_set_packing(png_ptr);
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED)
    /* Change the order of packed pixels to least significant bit first
     * (not useful if you are using png_set_packing). */
    if (transforms & PNG_TRANSFORM_PACKSWAP)
        png_set_packswap(png_ptr);
#endif

#if defined(PNG_READ_EXPAND_SUPPORTED)
    /* Expand paletted colors into true RGB triplets
     * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
     * Expand paletted or RGB images with transparency to full alpha
     * channels so the data will be available as RGBA quartets.
     */
    if (transforms & PNG_TRANSFORM_EXPAND)
        if ((png_ptr->bit_depth < 8) ||
                (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
                (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)))
            png_set_expand(png_ptr);
#endif

    /* We don't handle background color or gamma transformation or dithering. */

#if defined(PNG_READ_INVERT_SUPPORTED)
    /* invert monochrome files to have 0 as white and 1 as black */
    if (transforms & PNG_TRANSFORM_INVERT_MONO)
        png_set_invert_mono(png_ptr);
#endif

#if defined(PNG_READ_SHIFT_SUPPORTED)
    /* If you want to shift the pixel values from the range [0,255] or
     * [0,65535] to the original [0,7] or [0,31], or whatever range the
     * colors were originally in:
     */
    if ((transforms & PNG_TRANSFORM_SHIFT)
            && png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
    {
        png_color_8p sig_bit;

        png_get_sBIT(png_ptr, info_ptr, &sig_bit);
        png_set_shift(png_ptr, sig_bit);
    }
#endif

#if defined(PNG_READ_BGR_SUPPORTED)
    /* flip the RGB pixels to BGR (or RGBA to BGRA) */
    if (transforms & PNG_TRANSFORM_BGR)
        png_set_bgr(png_ptr);
#endif

#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED)
    /* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
    if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
        png_set_swap_alpha(png_ptr);
#endif

//.........这里部分代码省略.........

void __fastcall TPngDecoder::Init(){
    pfFile=fopen(FFileName.c_str(),"rb");
    if(!pfFile)
        throw Exception ( "Can't open file" );
    
    // first check the eight byte PNG signature
    fread(pbSig, 1, 8, pfFile);
    if (!png_check_sig(pbSig, 8))
        throw Exception ( "Bad file format" );

    // create the two png(-info) structures
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL,
        NULL, NULL);
    if (!png_ptr)
        throw Exception( "Not enough memory" );

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr)
    {
        png_destroy_read_struct(&png_ptr, NULL, NULL);
        throw Exception( "Not enough memory" );
    }
    /*точка возврата после обработки ошибки или предупреждения*/
    if (setjmp(png_jmpbuf(png_ptr)))
    {
    //    awp_res=*((long*)png_ptr->error_ptr);
        if(row_pointers){
            for (i = 0; i < FNumScanLines; i++){
                if(row_pointers[i])
                    free(row_pointers[i]);
            }
            free(row_pointers);
        }
        png_destroy_read_struct(&png_ptr, &info_ptr,NULL);
        if(pfFile) fclose(pfFile);
        throw Exception( "" );;
    }
    
    // initialize the input png file
    png_init_io(png_ptr, pfFile);

    //8 байт сигнатуры уже прочитанно
    png_set_sig_bytes(png_ptr, 8);

   
    /* The call to png_read_info() gives us all of the information from the
    * PNG file before the first IDAT (image data chunk).  REQUIRED
    */
    png_read_info(png_ptr, info_ptr);
    unsigned long width, hight;
    png_get_IHDR(png_ptr, info_ptr, &width, &hight, &iBitDepth, &iColorType,
        NULL, NULL, NULL);
    FWidth = width;
    FNumScanLines = hight;

   /**** Set up the data transformations you want.  Note that these are all
    **** optional.  Only call them if you want/need them.  Many of the
    **** transformations only work on specific types of images, and many
    **** are mutually exclusive.
    ****/

    /* tell libpng to strip 16 bit/color files down to 8 bits/color */
    //может это не нужно?
    if (iBitDepth == 16)
        png_set_strip_16(png_ptr);
    if (iBitDepth < 8)
        png_set_expand(png_ptr);
    
    
    /* Expand paletted colors into true RGB triplets */
    if (iColorType == PNG_COLOR_TYPE_PALETTE)
        png_set_expand(png_ptr);
    
        /* Expand paletted or RGB images with transparency to full alpha channels
        * so the data will be available as RGBA quartets.
    */
    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
        png_set_expand(png_ptr);
    
    /* tell libpng convert grayscale images to true rgd */
    if (iColorType == PNG_COLOR_TYPE_GRAY||
        iColorType == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png_ptr);
    /*remove alpha channel instead combine with background*/
    if (iColorType & PNG_COLOR_MASK_ALPHA)
        png_set_strip_alpha(png_ptr);

        /* Set the background color to draw transparent and alpha images over.
        * It is possible to set the red, green, and blue components directly
        * for paletted images instead of supplying a palette index.  Note that
        * even if the PNG file supplies a background, you are not required to
        * use it - you should use the (solid) application background if it has one.
    */

    // set the background color to draw transparent and alpha images over.
    if (png_get_bKGD(png_ptr, info_ptr, &pBackground))
        png_set_background(png_ptr, pBackground, PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
    /* flip the RGB pixels to BGR (or RGBA to BGRA) */
    if (iColorType & PNG_COLOR_MASK_COLOR)
        png_set_bgr(png_ptr);
//.........这里部分代码省略.........

void LoadPNG(const char *name, byte ** pic, int *width, int *height, byte alphaByte)
{
	int             bit_depth;
	int             color_type;
	png_uint_32     w;
	png_uint_32     h;
	unsigned int    row;
//	size_t          rowbytes;
	png_infop       info;
	png_structp     png;
	png_bytep      *row_pointers;
	byte           *data;
	byte           *out;
	int             size;

	// load png
	size = ri.FS_ReadFile(name, (void **)&data);

	if(!data)
		return;

	//png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	png = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp) NULL, png_user_error_fn, png_user_warning_fn);

	if(!png)
	{
		ri.Printf(PRINT_WARNING, "LoadPNG: png_create_write_struct() failed for (%s)\n", name);
		ri.FS_FreeFile(data);
		return;
	}

	// allocate/initialize the memory for image information.  REQUIRED
	info = png_create_info_struct(png);
	if(!info)
	{
		ri.Printf(PRINT_WARNING, "LoadPNG: png_create_info_struct() failed for (%s)\n", name);
		ri.FS_FreeFile(data);
		png_destroy_read_struct(&png, (png_infopp) NULL, (png_infopp) NULL);
		return;
	}

	/*
	 * Set error handling if you are using the setjmp/longjmp method (this is
	 * the common method of doing things with libpng).  REQUIRED unless you
	 * set up your own error handlers in the png_create_read_struct() earlier.
	 */
	if(setjmp(png_jmpbuf(png)))
	{
		// if we get here, we had a problem reading the file
		ri.Printf(PRINT_WARNING, "LoadPNG: first exception handler called for (%s)\n", name);
		ri.FS_FreeFile(data);
		png_destroy_read_struct(&png, (png_infopp) & info, (png_infopp) NULL);
		return;
	}

	//png_set_write_fn(png, buffer, png_write_data, png_flush_data);
	png_set_read_fn(png, data, png_read_data);

	png_set_sig_bytes(png, 0);

	// The call to png_read_info() gives us all of the information from the
	// PNG file before the first IDAT (image data chunk).  REQUIRED
	png_read_info(png, info);

	// get picture info
	png_get_IHDR(png, info, (png_uint_32 *) & w, (png_uint_32 *) & h, &bit_depth, &color_type, NULL, NULL, NULL);

	// tell libpng to strip 16 bit/color files down to 8 bits/color
	png_set_strip_16(png);

	// expand paletted images to RGB triplets
	if(color_type & PNG_COLOR_MASK_PALETTE)
		png_set_expand(png);

	// expand gray-scaled images to RGB triplets
	if(!(color_type & PNG_COLOR_MASK_COLOR))
		png_set_gray_to_rgb(png);

	// expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel
	//if(color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
	//  png_set_gray_1_2_4_to_8(png);

	// expand paletted or RGB images with transparency to full alpha channels
	// so the data will be available as RGBA quartets
	if(png_get_valid(png, info, PNG_INFO_tRNS))
		png_set_tRNS_to_alpha(png);

	// if there is no alpha information, fill with alphaByte
	if(!(color_type & PNG_COLOR_MASK_ALPHA))
		png_set_filler(png, alphaByte, PNG_FILLER_AFTER);

	// expand pictures with less than 8bpp to 8bpp
	if(bit_depth < 8)
		png_set_packing(png);

	// update structure with the above settings
	png_read_update_info(png, info);

	// allocate the memory to hold the image
	*width = w;
//.........这里部分代码省略.........

bool vtImage::_ReadPNG(const char *filename)
{
	FILE *fp = NULL;

	uchar header[8];
	png_structp png;
	png_infop   info;
	png_infop   endinfo;
	png_bytep  *row_p;

	png_uint_32 width, height;
	int depth, color;

	png_uint_32 i;
	png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	if (!png)
	{
		// We compiled against the headers of one version of libpng, but
		// linked against the libraries from another version.  If you get
		// this, fix the paths in your development environment.
		return false;
	}
	info = png_create_info_struct(png);
	endinfo = png_create_info_struct(png);

	fp = vtFileOpen(filename, "rb");
	if (fp && fread(header, 1, 8, fp) && png_check_sig(header, 8))
		png_init_io(png, fp);
	else
	{
		png_destroy_read_struct(&png, &info, &endinfo);
		return false;
	}
	png_set_sig_bytes(png, 8);

	png_read_info(png, info);
	png_get_IHDR(png, info, &width, &height, &depth, &color, NULL, NULL, NULL);

	if (color == PNG_COLOR_TYPE_GRAY || color == PNG_COLOR_TYPE_GRAY_ALPHA)
		png_set_gray_to_rgb(png);

	// never strip alpha
//	{
//		png_set_strip_alpha(png);
//		color &= ~PNG_COLOR_MASK_ALPHA;
//	}

	// Always expand paletted images
	if (color == PNG_COLOR_TYPE_PALETTE)
		png_set_expand(png);

	/*--GAMMA--*/
//	checkForGammaEnv();
	double screenGamma = 2.2 / 1.0;
#if 0
	// Getting the gamma from the PNG file is disabled here, since
	// PhotoShop writes bizarre gamma values like .227 (PhotoShop 5.0)
	// or .45 (newer versions)
	double	fileGamma;
	if (png_get_gAMA(png, info, &fileGamma))
		png_set_gamma(png, screenGamma, fileGamma);
	else
#endif
		png_set_gamma(png, screenGamma, 1.0/2.2);

	png_read_update_info(png, info);

	m_pPngData = (png_bytep) malloc(png_get_rowbytes(png, info)*height);
	row_p = (png_bytep *) malloc(sizeof(png_bytep)*height);

	bool StandardOrientation = true;
	for (i = 0; i < height; i++) {
		if (StandardOrientation)
			row_p[height - 1 - i] = &m_pPngData[png_get_rowbytes(png, info)*i];
		else
			row_p[i] = &m_pPngData[png_get_rowbytes(png, info)*i];
	}

	png_read_image(png, row_p);
	free(row_p);

	int iBitCount;

	switch (color)
	{
		case PNG_COLOR_TYPE_GRAY:
		case PNG_COLOR_TYPE_RGB:
		case PNG_COLOR_TYPE_PALETTE:
			iBitCount = 24;
			break;

		case PNG_COLOR_TYPE_GRAY_ALPHA:
		case PNG_COLOR_TYPE_RGB_ALPHA:
			iBitCount = 32;
			break;

		default:
			return false;
	}

//.........这里部分代码省略.........

static unsigned char* _load_image_RGBA_png(const char *fileName, int *width, int *height)
{
    // open the file
    FILE *fp = fopen(fileName, "rb");
    if (!fp)
        return _load_img_error(width, height);

    // read the header
    const size_t HEADER_LENGTH = 8;
    png_byte header[HEADER_LENGTH];
    size_t n = fread(header, 1, HEADER_LENGTH, fp);
    if (n != HEADER_LENGTH || png_sig_cmp(header, 0, HEADER_LENGTH))
        return _load_img_error(width, height);

    // try to create the loading structures
    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0,
      0);
    if (!png_ptr) {
        fclose(fp);
    return _load_img_error(width, height);
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, (png_infopp) 0, (png_infopp) 0);
        fclose(fp);
        return _load_img_error(width, height);
    }

    png_infop end_info = png_create_info_struct(png_ptr);
    if (!end_info) {
        png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)0);
        fclose(fp);
        return _load_img_error(width, height);
    }

    if (setjmp(png_ptr->jmpbuf)) {
        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
        fclose(fp);
        return _load_img_error(width, height);
    }

    // start the io
    png_init_io(png_ptr, fp);

    // indicate that we have already read some of the hearder
    png_set_sig_bytes(png_ptr, HEADER_LENGTH);

    // read the image info, get some info
    png_read_info(png_ptr, info_ptr);
    *width = png_get_image_width(png_ptr, info_ptr);
    *height = png_get_image_height(png_ptr, info_ptr);
    int bit_depth = png_get_bit_depth(png_ptr, info_ptr);
    png_byte color_type = png_get_color_type(png_ptr, info_ptr);

    // force the image into RGBA, 8 bits per channel
    if (color_type != PNG_COLOR_TYPE_RGBA)
        png_set_expand(png_ptr);
    if (color_type == PNG_COLOR_TYPE_GRAY ||
      color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png_ptr);
    if (bit_depth < 8)
        png_set_packing(png_ptr);
    else if (bit_depth == 16)
        png_set_strip_16(png_ptr);
    if (color_type != PNG_COLOR_TYPE_RGBA)
        png_set_filler(png_ptr, 255, PNG_FILLER_AFTER);
    png_read_update_info(png_ptr, info_ptr);

    // make sure we're actually in rgba mode
    if ((int)png_get_rowbytes(png_ptr, info_ptr) != ((*width) * 4)) {
        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
        fclose(fp);
        return _load_img_error(width, height);
    }

    // finally, read the file
    unsigned char *buffer = (unsigned char *) malloc((*width) * (*height) * 4);
    png_bytep *row_pointers = new png_bytep[*height];
    for (int y = 0 ; y < (*height) ; y++) {
        row_pointers[y] = (png_byte *) (buffer + ((*height) - 1 - y) *
          (*width) * 4);
    }
    png_read_rows(png_ptr, row_pointers, 0, (long unsigned int) (*height));

    // deallocate memory and return
    fclose(fp);
    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
    return buffer;
}

bool GR_Win32Image::_convertFromPNG(const UT_ByteBuf* pBB, UT_sint32 iDisplayWidth, UT_sint32 iDisplayHeight)
{
	png_structp png_ptr;
	png_infop info_ptr;
	png_uint_32 width, height;
	int bit_depth, color_type, interlace_type;

	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (void*) NULL,
									 NULL, NULL);

	if (png_ptr == NULL)
	{
		return false;
	}

	/* Allocate/initialize the memory for image information.  REQUIRED. */
	info_ptr = png_create_info_struct(png_ptr);
	if (info_ptr == NULL)
	{
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		return false;
	}

	/* Set error handling if you are using the setjmp/longjmp method (this is
	 * the normal method of doing things with libpng).  REQUIRED unless you
	 * set up your own error handlers in the png_create_read_struct() earlier.
	 */
	if (setjmp(png_jmpbuf(png_ptr)))
	{
		/* Free all of the memory associated with the png_ptr and info_ptr */
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);

		/* If we get here, we had a problem reading the file */
		return false;
	}

	struct _bb myBB;
	myBB.pBB = pBB;
	myBB.iCurPos = 0;
	
	png_set_read_fn(png_ptr, (void *)&myBB, _png_read);

	/* The call to png_read_info() gives us all of the information from the
	 * PNG file before the first IDAT (image data chunk).  REQUIRED
	 */
	png_read_info(png_ptr, info_ptr);

	png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
				 &interlace_type, NULL, NULL);

	/* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
	 * byte into separate bytes (useful for paletted and grayscale images).
	 */
	png_set_packing(png_ptr);

	/* Expand paletted colors into true RGB triplets */
	png_set_expand(png_ptr);

	/*  If we've got images with 16 bits per channel, we don't need that
		much precision.  We'll do fine with 8 bits per channel */
	png_set_strip_16(png_ptr);

	/*  For simplicity, treat grayscale as RGB */
	png_set_gray_to_rgb(png_ptr);

	/*  For simplicity, we'll ignore alpha */
	png_set_strip_alpha(png_ptr);
	
	/*  We want libpng to deinterlace the image for us */
	UT_uint32 iInterlacePasses = png_set_interlace_handling(png_ptr);

	/* flip the RGB pixels to BGR (or RGBA to BGRA) */
	png_set_bgr(png_ptr);

	UT_uint32 iBytesInRow = width * 3;
	if (iBytesInRow % 4)
	{
		iBytesInRow += (4 - (iBytesInRow % 4));
	}

	m_pDIB = (BITMAPINFO*) g_try_malloc(sizeof(BITMAPINFOHEADER) + height * iBytesInRow);
	if (!m_pDIB)
	{
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		return false;
	}

	/*
	  Note that we do NOT create a DIB of iDisplayWidth,iDisplayHeight, since
	  DIBs can be stretched automatically by the Win32 API.  So we simply remember
	  the display size for drawing later.
	*/

	setDisplaySize(iDisplayWidth, iDisplayHeight);

	m_pDIB->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	m_pDIB->bmiHeader.biWidth = width;
	m_pDIB->bmiHeader.biHeight = height;
	m_pDIB->bmiHeader.biPlanes = 1;
	m_pDIB->bmiHeader.biBitCount = 24;
//.........这里部分代码省略.........

void readPng(GImage* pImage, const unsigned char* pData, size_t nDataSize)
{
	// Check for the PNG signature
	if(nDataSize < 8 || png_sig_cmp((png_bytep)pData, 0, 8) != 0)
		throw Ex("not a png file");

	// Read all PNG data up until the image data chunk.
	GPNGReader reader(pData);
	png_set_read_fn(reader.m_pReadStruct, (png_voidp)&reader, (png_rw_ptr)readFunc);
	png_read_info(reader.m_pReadStruct, reader.m_pInfoStruct);

	// Get the image data
	int depth, color;
	png_uint_32 width, height;
	png_get_IHDR(reader.m_pReadStruct, reader.m_pInfoStruct, &width, &height, &depth, &color, NULL, NULL, NULL);
	if(depth != 8)
		throw Ex("unexpected depth");
	pImage->resize(width, height);

	// Set gamma correction
	double dGamma;
	if (png_get_gAMA(reader.m_pReadStruct, reader.m_pInfoStruct, &dGamma))
		png_set_gamma(reader.m_pReadStruct, 2.2, dGamma);
	else
		png_set_gamma(reader.m_pReadStruct, 2.2, 1.0 / 2.2); // 1.0 = viewing gamma, 2.2 = screen gamma

	// Update the 'info' struct with the gamma information
	png_read_update_info(reader.m_pReadStruct, reader.m_pInfoStruct);

	// Tell it to expand palettes to full channels
	png_set_expand(reader.m_pReadStruct);
	png_set_gray_to_rgb(reader.m_pReadStruct);

	// Allocate the row pointers
	unsigned long rowbytes = png_get_rowbytes(reader.m_pReadStruct, reader.m_pInfoStruct);
	unsigned long channels = rowbytes / width;
	png_bytep pRawData = (png_bytep)new unsigned char[rowbytes * height];
	unsigned int i;
	{
		png_bytep* pRows = (png_bytep*)new unsigned char[sizeof(png_bytep) * height];
		for(i = 0; i < height; i++)
			pRows[i] = pRawData + i * rowbytes;
		png_read_image(reader.m_pReadStruct, pRows);
		delete[] pRows;
	}

	// Copy to the GImage
	unsigned long nPixels = width * height;
	unsigned int* pRGBQuads = pImage->m_pPixels;
	unsigned char *pBytes = pRawData;
	if(channels > 3)
	{
		if(channels != 4)
			throw Ex("Unexpected number of channels");
		for(i = 0; i < nPixels; i++)
		{
			*pRGBQuads = gARGB(pBytes[3], pBytes[0], pBytes[1], pBytes[2]);
			pBytes += channels;
			pRGBQuads++;
		}
	}
	else if(channels == 3)
	{
		for(i = 0; i < nPixels; i++)
		{
			*pRGBQuads = gARGB(0xff, pBytes[0], pBytes[1], pBytes[2]);
			pBytes += channels;
			pRGBQuads++;
		}
	}
	else
	{
		delete[] pRawData;
		throw Ex("Sorry, loading ", to_str(channels), "-channel png files is not yet supported");
	}
	delete[] pRawData;

	// Check for additional tags
	png_read_end(reader.m_pReadStruct, reader.m_pEndInfoStruct);
}

SDL_Surface *TCOD_sys_read_png(const char *filename) {
	png_uint_32 png_width,png_height,y;
	int png_bit_depth,png_color_type,png_interlace_type;
	png_structp png_ptr;
	png_infop info_ptr;
	FILE *fp;
	SDL_Surface *bitmap;
	png_bytep *row_pointers;

	if ((fp = fopen(filename, "rb")) == NULL)
		return NULL;
	/* Create and initialize the png_struct with the desired error handler
	* functions.  If you want to use the default stderr and longjump method,
	* you can supply NULL for the last three parameters.  We also supply the
	* the compiler header file version, so that we know if the application
	* was compiled with a compatible version of the library.  REQUIRED
	*/
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,NULL, NULL, NULL);

	if (png_ptr == NULL)
	{
		fclose(fp);
		return NULL;
	}

	/* Allocate/initialize the memory for image information.  REQUIRED. */
	info_ptr = png_create_info_struct(png_ptr);
	if (info_ptr == NULL)
	{
		fclose(fp);
		png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
		return NULL;
	}

	/* Set error handling if you are using the setjmp/longjmp method (this is
	* the normal method of doing things with libpng).  REQUIRED unless you
	* set up your own error handlers in the png_create_read_struct() earlier.
	*/

	if (setjmp(png_jmpbuf(png_ptr)))
	{
		/* Free all of the memory associated with the png_ptr and info_ptr */
		png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
		fclose(fp);
		/* If we get here, we had a problem reading the file */
		return NULL;
	}

	png_init_io(png_ptr, fp);

	/*
	* If you have enough memory to read in the entire image at once,
	* and you need to specify only transforms that can be controlled
	* with one of the PNG_TRANSFORM_* bits (this presently excludes
	* dithering, filling, setting background, and doing gamma
	* adjustment), then you can read the entire image (including
	* pixels) into the info structure with this call:
	*/
	//png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, png_voidp_NULL);

	// get info about the image
	png_read_info(png_ptr,info_ptr);
	png_get_IHDR(png_ptr,info_ptr,&png_width,&png_height,&png_bit_depth,&png_color_type,
		&png_interlace_type,NULL,NULL);

	// convert the image to a format suitable with libtcod
	png_set_strip_16(png_ptr); // 16 bits channels => 8 bits channels
	png_set_packing(png_ptr); // 1,2,4 bits depth => 24/32 bits depth
	if ( png_color_type == PNG_COLOR_TYPE_GRAY ) png_set_expand(png_ptr); // grayscale => color
	if ( png_color_type == PNG_COLOR_TYPE_GRAY_ALPHA ) png_set_gray_to_rgb(png_ptr);

	// update the image information
	png_read_update_info(png_ptr,info_ptr);
	png_get_IHDR(png_ptr,info_ptr,&png_width,&png_height,&png_bit_depth,&png_color_type,
		&png_interlace_type,NULL,NULL);

	// create the SDL surface
	bitmap=TCOD_sys_get_surface(png_width,png_height,info_ptr->channels == 4);

	// get row data
	row_pointers=(png_bytep *)malloc(sizeof(png_bytep)*png_height);
	for (y=0; y<  png_height; y++ ) {
		row_pointers[y]=(png_bytep)(Uint8 *)(bitmap->pixels) + y * bitmap->pitch;
	}

	// read png data directly into the SDL surface
	png_read_image(png_ptr,row_pointers);

	/* clean up after the read, and free any memory allocated - REQUIRED */
	png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
	free(row_pointers);

	/* close the file */
	fclose(fp);
	return bitmap;
}

void PNGImageDecoder::headerAvailable()
{
    png_structp png = m_reader->pngPtr();
    png_infop info = m_reader->infoPtr();
    png_uint_32 width = png_get_image_width(png, info);
    png_uint_32 height = png_get_image_height(png, info);

    // Protect against large PNGs. See http://bugzil.la/251381 for more details.
    const unsigned long maxPNGSize = 1000000UL;
    if (width > maxPNGSize || height > maxPNGSize) {
        longjmp(JMPBUF(png), 1);
        return;
    }

    // Set the image size now that the image header is available.
    if (!setSize(width, height)) {
        longjmp(JMPBUF(png), 1);
        return;
    }

    int bitDepth, colorType, interlaceType, compressionType, filterType, channels;
    png_get_IHDR(png, info, &width, &height, &bitDepth, &colorType, &interlaceType, &compressionType, &filterType);

    // The options we set here match what Mozilla does.

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

    png_bytep trns = 0;
    int trnsCount = 0;
    if (png_get_valid(png, info, PNG_INFO_tRNS)) {
        png_get_tRNS(png, info, &trns, &trnsCount, 0);
        png_set_expand(png);
    }

    if (bitDepth == 16)
        png_set_strip_16(png);

    if (colorType == PNG_COLOR_TYPE_GRAY || colorType == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png);

#if USE(QCMSLIB)
    if ((colorType & PNG_COLOR_MASK_COLOR) && !m_ignoreGammaAndColorProfile) {
        // We only support color profiles for color PALETTE and RGB[A] PNG. Supporting
        // color profiles for gray-scale images is slightly tricky, at least using the
        // CoreGraphics ICC library, because we expand gray-scale images to RGB but we
        // do not similarly transform the color profile. We'd either need to transform
        // the color profile or we'd need to decode into a gray-scale image buffer and
        // hand that to CoreGraphics.
        bool sRGB = false;
        ColorProfile colorProfile;
        getColorProfile(png, info, colorProfile, sRGB);
        bool imageHasAlpha = (colorType & PNG_COLOR_MASK_ALPHA) || trnsCount;
        m_reader->createColorTransform(colorProfile, imageHasAlpha, sRGB);
        m_hasColorProfile = !!m_reader->colorTransform();
    }
#endif

    if (!m_hasColorProfile) {
        // Deal with gamma and keep it under our control.
        const double inverseGamma = 0.45455;
        const double defaultGamma = 2.2;
        double gamma;
        if (!m_ignoreGammaAndColorProfile && png_get_gAMA(png, info, &gamma)) {
            const double maxGamma = 21474.83;
            if ((gamma <= 0.0) || (gamma > maxGamma)) {
                gamma = inverseGamma;
                png_set_gAMA(png, info, gamma);
            }
            png_set_gamma(png, defaultGamma, gamma);
        } else {
            png_set_gamma(png, defaultGamma, inverseGamma);
        }
    }

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

    // Update our info now.
    png_read_update_info(png, info);
    channels = png_get_channels(png, info);
    ASSERT(channels == 3 || channels == 4);

    m_reader->setHasAlpha(channels == 4);

    if (m_reader->decodingSizeOnly()) {
        // If we only needed the size, halt the reader.
#if PNG_LIBPNG_VER_MAJOR > 1 || (PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR >= 5)
        // '0' argument to png_process_data_pause means: Do not cache unprocessed data.
        m_reader->setReadOffset(m_reader->currentBufferSize() - png_process_data_pause(png, 0));
#else
        m_reader->setReadOffset(m_reader->currentBufferSize() - png->buffer_size);
        png->buffer_size = 0;
#endif
    }
}

bool ossimPngReader::initReader()
{
   bool result = true;
   
   ossim_uint32 height    = png_get_image_height(m_pngReadPtr, m_pngReadInfoPtr);
   ossim_uint32 width     = png_get_image_width(m_pngReadPtr, m_pngReadInfoPtr);
   m_bitDepth            = png_get_bit_depth(m_pngReadPtr, m_pngReadInfoPtr);
   m_pngColorType        = png_get_color_type(m_pngReadPtr, m_pngReadInfoPtr);
   
   m_imageRect = ossimIrect(0, 0, width  - 1, height - 1);
   
   if (m_bitDepth == 16)
   {
      // png_set_strip_16 (m_pngReadPtr);
      m_bytePerPixelPerBand = 2;
      m_outputScalarType = OSSIM_UINT16;
   }
   else
   {
      m_bytePerPixelPerBand = 1;
   }

   // Set the read mode from scalar and color type.
   if (m_outputScalarType == OSSIM_UINT8)
   {
      if ( (m_pngColorType == PNG_COLOR_TYPE_RGB_ALPHA) ||
           (m_pngColorType == PNG_COLOR_TYPE_GRAY_ALPHA) )
      {
         m_readMode = ossimPngRead8a;
      }
      else
      {
         m_readMode = ossimPngRead8;
      }
   }
   else
   {
      if ( (m_pngColorType == PNG_COLOR_TYPE_RGB_ALPHA) ||
           (m_pngColorType == PNG_COLOR_TYPE_GRAY_ALPHA) )
      {
         m_readMode = ossimPngRead16a;
      }
      else
      {
         m_readMode = ossimPngRead16;
      }

      // Set the swap flag.  PNG stores data in network byte order(big endian).
      if(ossim::byteOrder() == OSSIM_LITTLE_ENDIAN)
      {
         m_swapFlag = true;
      }
   }
   
   //---
   // If png_set_expand used:
   // Expand data to 24-bit RGB, or 8-bit grayscale,
   // with alpha if available.
   //---
   bool expandFlag = false;

   if ( m_pngColorType == PNG_COLOR_TYPE_PALETTE )
   {
      expandFlag = true;
   }
   if ( (m_pngColorType == PNG_COLOR_TYPE_GRAY) && (m_bitDepth < 8) )
   {
      expandFlag = true;
   }
   if ( png_get_valid(m_pngReadPtr, m_pngReadInfoPtr, PNG_INFO_tRNS) )
   {
      expandFlag = true;
   }

   //---
   // If png_set_packing used:
   // Use 1 byte per pixel in 1, 2, or 4-bit depth files. */
   //---
   bool packingFlag = false;

   if ( (m_bitDepth < 8) && (m_pngColorType == PNG_COLOR_TYPE_GRAY) )
   {
      packingFlag = true;
   }

   if (expandFlag)
   {
       png_set_expand(m_pngReadPtr);
   }
   if (packingFlag)
   {
      png_set_packing(m_pngReadPtr);
   }

   // Gamma correction.
   // ossim_float64 gamma;
   // if (png_get_gAMA(m_pngReadPtr, m_pngReadInfoPtr, &gamma))
   // {
   //    png_set_gamma(png_ptr, display_exponent, gamma);
   // }
//.........这里部分代码省略.........

void ossimPngReader::restart()
{
   if ( m_str )
   {
      // Destroy the existing memory associated with png structs.
      if (m_pngReadPtr && m_pngReadInfoPtr)
      {
         png_destroy_read_struct(&m_pngReadPtr, &m_pngReadInfoPtr, NULL);
      }

      m_pngReadPtr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
                                            NULL,
                                            NULL,
                                            NULL);
      m_pngReadInfoPtr = png_create_info_struct(m_pngReadPtr);

      if ( setjmp( png_jmpbuf(m_pngReadPtr) ) )
      {
         ossimNotify(ossimNotifyLevel_WARN)
            << "Error while reading.  File corrupted?  "
            << theImageFile
            << std::endl;
      
         return;
      }

      // Reset the file pointer.
      m_str->seekg( m_restartPosition, std::ios_base::beg );
   
      //---
      // Pass the static read method to libpng to allow us to use our
      // c++ stream instead of doing "png_init_io (pp, ...);" with
      // c stream.
      //---
      png_set_read_fn( m_pngReadPtr,
                       (png_voidp)m_str,
                       (png_rw_ptr)&ossimPngReader::pngReadData );

      //---
      // Note we won't do png_set_sig_bytes(png_ptr, 8) here because we are not
      // rechecking for png signature.
      //---
      png_read_info(m_pngReadPtr, m_pngReadInfoPtr);

      //---
      // If png_set_expand used:
      // Expand data to 24-bit RGB, or 8-bit grayscale,
      // with alpha if available.
      //---
      bool expandFlag = false;

      if ( m_pngColorType == PNG_COLOR_TYPE_PALETTE )
      {
         expandFlag = true;
      }
      if ( (m_pngColorType == PNG_COLOR_TYPE_GRAY) && (m_bitDepth < 8) )
      {
         expandFlag = true;
      }
      if ( png_get_valid(m_pngReadPtr, m_pngReadInfoPtr, PNG_INFO_tRNS) )
      {
         expandFlag = true;
      }

      //---
      // If png_set_packing used:
      // Use 1 byte per pixel in 1, 2, or 4-bit depth files. */
      //---
      bool packingFlag = false;

      if ( (m_bitDepth < 8) && (m_pngColorType == PNG_COLOR_TYPE_GRAY) )
      {
         packingFlag = true;
      }

      if (expandFlag)
      {
         png_set_expand(m_pngReadPtr);
      }
      if (packingFlag)
      {
         png_set_packing(m_pngReadPtr);
      }

      // Gamma correction.
      //    ossim_float64 gamma;
      //    if (png_get_gAMA(m_pngReadPtr, m_pngReadInfoPtr, &gamma))
      //    {
      //       png_set_gamma(m_pngReadPtr, display_exponent, gamma);
      //    }

      //---
      // Turn on interlace handling... libpng returns just 1 (ie single pass)
      //  if the image is not interlaced
      //---
      png_set_interlace_handling (m_pngReadPtr);

      //---
      // Update the info structures after the transformations take effect
      //---
//.........这里部分代码省略.........

void* replaceBootImage(AbstractFile* imageWrapper, const unsigned int* key, const unsigned int* iv, AbstractFile* png, size_t *fileSize) {
	AbstractFile* imageFile;
	unsigned char header[8];
	InfoIBootIM* info;
	png_uint_32 i;
	png_bytepp row_pointers;
	
	uint8_t* imageBuffer;
	void* buffer;

	png->read(png, header, 8);
	if(png_sig_cmp(header, 0, 8) != 0) {
		XLOG(0, "error: not a valid png file\n");
		return NULL;
	}
	png->seek(png, 0);

	png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, pngError, pngWarn);
	if (!png_ptr) {
		return NULL;
	}

	png_infop info_ptr = png_create_info_struct(png_ptr);
	if (!info_ptr)
	{
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		return NULL;
	}

	png_infop end_info = png_create_info_struct(png_ptr);
	if (!end_info)
	{
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		return NULL;
	}

	if (setjmp(png_jmpbuf(png_ptr)))
	{
		XLOG(0, "error reading png\n");
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		free(buffer);
		return NULL;
	}

	png_set_read_fn(png_ptr, png, pngRead);

	png_read_info(png_ptr, info_ptr);
	
	if(png_get_bit_depth(png_ptr, info_ptr) > 8) {
		XLOG(0, "warning: bit depth per channel is greater than 8 (%d). Attempting to strip, but image quality will be degraded.\n", png_get_bit_depth(png_ptr, info_ptr));
	}
	
	if(png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_GRAY || png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_RGB) {
		XLOG(0, "notice: attempting to add dummy transparency channel\n");
	}
	
	if(png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_PALETTE) {
		XLOG(0, "notice: attempting to expand palette into full rgb\n");
	}
	
	png_set_expand(png_ptr);
	png_set_strip_16(png_ptr);
	png_set_bgr(png_ptr);
	png_set_add_alpha(png_ptr, 0x0, PNG_FILLER_AFTER);
	png_set_invert_alpha(png_ptr);
	
	png_read_update_info(png_ptr, info_ptr);
	

	if(png_get_image_width(png_ptr, info_ptr) > 320 || png_get_image_height(png_ptr, info_ptr) > 480) {
		XLOG(0, "error: dimensions out of range, must be within 320x480, not %lux%lu\n", png_get_image_width(png_ptr, info_ptr), png_get_image_height(png_ptr, info_ptr));
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return NULL;
	}

	if(png_get_bit_depth(png_ptr, info_ptr) != 8) {
		XLOG(0, "error: bit depth per channel must be 8 not %d!\n", png_get_bit_depth(png_ptr, info_ptr));
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return NULL;
	}

	if(png_get_color_type(png_ptr, info_ptr) != PNG_COLOR_TYPE_GRAY_ALPHA && png_get_color_type(png_ptr, info_ptr) != PNG_COLOR_TYPE_RGB_ALPHA) {
		XLOG(0, "error: incorrect color type, must be greyscale with alpha, or rgb with alpha\n");
		if(png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_GRAY || png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_RGB) {
			XLOG(0, "It appears you're missing an alpha channel. Add transparency to your image\n");
		}
		if(png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_PALETTE) {
			XLOG(0, "This PNG is saved with the palette color type rather than ARGB.\n");
		}
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);

		return NULL;
	}

	row_pointers = (png_bytepp) malloc(sizeof(png_bytep) * png_get_image_height(png_ptr, info_ptr));
	imageBuffer = malloc(png_get_image_height(png_ptr, info_ptr) * png_get_rowbytes(png_ptr, info_ptr));
	for(i = 0; i < png_get_image_height(png_ptr, info_ptr); i++) {
		row_pointers[i] = imageBuffer + (png_get_rowbytes(png_ptr, info_ptr) * i);
	}

//.........这里部分代码省略.........

//.........这里部分代码省略.........
  // This tells libPNG that we have already read 8 bytes from the start
  // of the file (for the header check above).
  png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK);

  // This reads the PNG file into the read and info structs
  /*
   * If you have enough memory to read in the entire image at once,
   * and you need to specify only transforms that can be controlled
   * with one of the PNG_TRANSFORM_* bits (this presently excludes
   * dithering, filling, setting background, and doing gamma
   * adjustment), then you can read the entire image (including
   * pixels) into the info structure with this call:
   */
  png_read_info(png_ptr, info_ptr);

  // Get some basic infos about the image from png_info structure
  // width & height in px, bit depth
  // interlace_method, compression_method, & filter_method are ignored
  png_get_IHDR(png_ptr, info_ptr, &(pImagePNG->sizeX), &(pImagePNG->sizeY), 
	       &bit_depth, &cType, 0, 0, 0);

  // COLOR TYPE read and possible corrections - then reread
  // Color type: we handle RGB and RGB_ALPHA (with Alpha) 
  // GRAY (luminance) and GRAY_ALPHA (luminance with Alpha)
  cType = png_get_color_type(png_ptr, info_ptr);
  // strip the pixels of a PNG stream with 16 bits per channel to 8 bits per channel
  if (bit_depth == 16) {
    png_set_strip_16(png_ptr);
  }
  // set transformation in png_ptr such that paletted images are expanded to RGB, 
  // grayscale images of bit-depth less than 8 are expanded to 8-bit images
  // tRNS chunks are expanded to alpha channels
  if (cType == PNG_COLOR_TYPE_PALETTE) {
    png_set_expand(png_ptr);
  }
  if (bit_depth < 8) {
    png_set_expand(png_ptr);
  }
  if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
    png_set_expand(png_ptr);
  }
  // if required set gamma conversion
  if (png_get_gAMA(png_ptr, info_ptr, &gamma)) {
    png_set_gamma(png_ptr, (double) 2.2, gamma);
  }

  // After the image transformations have been registered update info_ptr data
  png_read_update_info(png_ptr, info_ptr);
  // Gets again width, height and the new bit-depth and color-type
  png_get_IHDR(png_ptr, info_ptr, &(pImagePNG->sizeX), &(pImagePNG->sizeY), 
	       &bit_depth, &cType, 0, 0, 0);

  // We now calculate the *bytes* per pixel from the color type and the
  // bits per pixel.
  if((cType == PNG_COLOR_TYPE_RGB) && (bit_depth == 8)) {
    pImagePNG->bytesPerPixel = 3;
    *hasAlpha = false;
  }
  else if((cType == PNG_COLOR_TYPE_RGB_ALPHA) && (bit_depth == 8)) {
    pImagePNG->bytesPerPixel = 4;
    *hasAlpha = true;
  }
  else if((cType == PNG_COLOR_TYPE_GRAY) && (bit_depth == 8)) {
    pImagePNG->bytesPerPixel = 1;
    *hasAlpha = false;
  }

uint8 *readpng_get_image(void * strsv, uint32 *pChannels, uint32 *pRowbytes, uint32 *pWidth, uint32 *pHeight)
{
    readpng_structs_t * strs = (readpng_structs_t *)strsv;

  png_uint_32  width, height;
  int  bit_depth, color_type;
  uint8  *image_data = NULL;
  png_uint_32  i, rowbytes;
  png_bytepp  row_pointers = NULL;


    /* alternatively, could make separate calls to png_get_image_width(),
     * etc., but want bit_depth and color_type for later [don't care about
     * compression_type and filter_type => NULLs] */

  png_get_IHDR(strs->png_ptr, strs->info_ptr, &width, &height, &bit_depth, &color_type,
               NULL, NULL, NULL);

  *pWidth = width;
  *pHeight = height;

    /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits,
     * transparency chunks to full alpha channel; strip 16-bit-per-sample
     * images to 8 bits per sample; and convert grayscale to RGB[A] */

    if (color_type == PNG_COLOR_TYPE_PALETTE)
        png_set_expand(strs->png_ptr);
    if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
        png_set_expand(strs->png_ptr);
    if (png_get_valid(strs->png_ptr, strs->info_ptr, PNG_INFO_tRNS))
        png_set_expand(strs->png_ptr);
    if (bit_depth == 16)
        png_set_strip_16(strs->png_ptr);
    if (color_type == PNG_COLOR_TYPE_GRAY ||
        color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(strs->png_ptr);

    /* all transformations have been registered; now update info_ptr data,
     * get rowbytes and channels, and allocate image memory */

    png_read_update_info(strs->png_ptr, strs->info_ptr);

    *pRowbytes = rowbytes = png_get_rowbytes(strs->png_ptr, strs->info_ptr);
    *pChannels = (int)png_get_channels(strs->png_ptr, strs->info_ptr);

    if ((image_data = (uint8 *)malloc(rowbytes*height)) == NULL) {
        png_destroy_read_struct(&strs->png_ptr, &strs->info_ptr, NULL);
        return NULL;
    }
    if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
        png_destroy_read_struct(&strs->png_ptr, &strs->info_ptr, NULL);
        free(image_data);
        image_data = NULL;
        return NULL;
    }

    Trace((stderr, "readpng_get_image:  channels = %d, rowbytes = %ld, height = %ld\n", *pChannels, rowbytes, height));


    /* set the individual row_pointers to point at the correct offsets */

    for (i = 0;  i < height;  ++i)
        row_pointers[i] = image_data + i*rowbytes;

    /* now we can go ahead and just read the whole image */

    png_read_image(strs->png_ptr, row_pointers);

    free(row_pointers);
    row_pointers = NULL;

    png_read_end(strs->png_ptr, NULL);

    return image_data;
}