C++ png_sig_cmp函数代码示例

void png_load_from_memory(aasset_buffer_t& buf, raw_bitmap_t* out_bitmap)
{
    //png header - 8 bytes
    if (png_sig_cmp(buf.data(), 0, 8))
    {
        my_assert(false && "Couldn't load texture. It isn't png file.");
        return;
    }

    auto png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    my_assert(png_ptr && "Couldn't load texture. Png load error.");
    MAKE_GUARD(png_ptr, [](decltype(png_ptr) ptr)
    {   png_destroy_read_struct(&ptr, (png_infopp)NULL, (png_infopp)NULL);});

    auto info_ptr = png_create_info_struct(png_ptr);
    my_assert(info_ptr && "Couldn't load texture. Png load error.");
    auto info_deleter = [png_ptr](decltype(info_ptr) ptr)
    {   png_destroy_info_struct(png_ptr, &ptr);};
    MAKE_GUARD(info_ptr, info_deleter);

    // the code in this if statement gets called if libpng encounters an error
    if (setjmp((long*) png_jmpbuf(png_ptr)))
    {
        my_assert(false && "error from libpng");
        return;
    }

    png_set_read_fn(png_ptr, &buf, read_from_aasset_buffer);
    // tell libpng we already read the signature
    png_set_sig_bytes(png_ptr, 8);
    buf.seek(8);

    png_read_info(png_ptr, info_ptr);

    png_uint_32 width = 0;
    png_uint_32 height = 0;
    int bitDepth = 0;
    int colorType = -1;
    auto res = png_get_IHDR(png_ptr, info_ptr, &width, &height, &bitDepth, &colorType, NULL, NULL, NULL);
    my_assert(res == 1);

    bool transparency = false;
    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
    {
        png_set_tRNS_to_alpha(png_ptr);
        transparency = true;
    }
    // Expands PNG with less than 8bits per channel to 8bits.
    if (bitDepth < 8)
    {
        png_set_packing(png_ptr);
        // Shrinks PNG with 16bits per color channel down to 8bits.
    }
    else if (bitDepth == 16)
    {
        png_set_strip_16(png_ptr);
    }

    uint32_t format = 0;
    switch (colorType)
    {
        case PNG_COLOR_TYPE_RGB:
            format = transparency ? GL_RGBA : GL_RGB;
            break;

        case PNG_COLOR_TYPE_RGBA:
            format = GL_RGBA;
            break;

        case PNG_COLOR_TYPE_PALETTE:
        {
            png_set_palette_to_rgb(png_ptr);
            format = transparency ? GL_RGBA : GL_RGB;
            break;
        }
        default:
            my_assert(false && "Png read error. Uknown color type");
            return;
    }
    //apply transformations
    png_read_update_info(png_ptr, info_ptr);

    out_bitmap->init(width, height, format);

    auto row_size = png_get_rowbytes(png_ptr, info_ptr);
    my_assert(row_size > 0);
    my_assert(row_size == width * out_bitmap->bytes_per_pixel());

    auto row_ptrs = new png_bytep[height];
    MAKE_GUARD(row_ptrs, [](decltype(row_ptrs) ptr)
    {   delete[] ptr;});

    for (int32_t i = 0; i < height; ++i)
    {
        row_ptrs[height - (i + 1)] = out_bitmap->get_row(i);
    }

    png_read_image(png_ptr, row_ptrs);
}

TypedImage LoadPng(const std::string& filename)
{
#ifdef HAVE_PNG
    FILE *in = fopen(filename.c_str(), "rb");
    
    if( in )  {
        //check the header
        const size_t nBytes = 8;
        png_byte header[nBytes];
        size_t nread = fread(header, 1, nBytes, in);
        int nIsPNG = png_sig_cmp(header, 0, nread);
        
        if ( nIsPNG != 0 )  {
            throw std::runtime_error( filename + " is not a PNG file" );
        }
        
        //set up initial png structs
        png_structp png_ptr = png_create_read_struct( PNG_LIBPNG_VER_STRING, (png_voidp)NULL, NULL, &PngWarningsCallback);
        if (!png_ptr) {
            throw std::runtime_error( "PNG Init error 1" );
        }
        
        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);
            throw std::runtime_error( "PNG Init error 2" );
        }
        
        png_infop end_info = png_create_info_struct(png_ptr);
        if (!end_info) {
            png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
            throw std::runtime_error( "PNG Init error 3" );
        }
        
        png_init_io(png_ptr, in);
        png_set_sig_bytes(png_ptr, nBytes);
        
        //read the file
        png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
        
        if( png_get_bit_depth(png_ptr, info_ptr) == 1)  {
            //Unpack bools to bytes to ease loading.
            png_set_packing(png_ptr);
        } else if( png_get_bit_depth(png_ptr, info_ptr) < 8) {
            //Expand nonbool colour depths up to 8bpp
            png_set_expand_gray_1_2_4_to_8(png_ptr);
        }
        
        //Get rid of palette, by transforming it to RGB
        if(png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_PALETTE) {
            png_set_palette_to_rgb(png_ptr);
        }
        
        if( png_get_interlace_type(png_ptr,info_ptr) != PNG_INTERLACE_NONE) {
            throw std::runtime_error( "Interlace not yet supported" );
        }
        
        const size_t w = png_get_image_width(png_ptr,info_ptr);
        const size_t h = png_get_image_height(png_ptr,info_ptr);
        const size_t pitch = png_get_rowbytes(png_ptr, info_ptr);
        
        TypedImage img;
        img.Alloc(w, h, PngFormat(png_ptr, info_ptr), pitch);
        
        png_bytepp rows = png_get_rows(png_ptr, info_ptr);
        for( unsigned int r = 0; r < h; r++) {
            memcpy( img.ptr + pitch*r, rows[r], pitch );
        }
        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
        
        fclose(in);
        return img;
    }
    
    throw std::runtime_error("Unable to load PNG file, '" + filename + "'");    
    
#else
    throw std::runtime_error("PNG Support not enabled. Please rebuild Pangolin.");
#endif
}

void png::load(const std::string& file_name)
{
    // unfortunately, we need to break down to the C-code level here, since
    // libpng is written in C itself

    // we need to open the file in binary mode
    FILE* fp = fopen(file_name.c_str(), "rb");
    if (!fp)
    {
        throw std::runtime_error{"failed to open " + file_name};
    }

    // read in the header (max size of 8), use it to validate this as a png file
    png_byte header[8];
    fread(header, 1, 8, fp);
    if (png_sig_cmp(header, 0, 8))
    {
        fclose(fp);
        throw std::runtime_error{file_name + " is not a valid png file"};
    }

    // set up libpng structs for reading info
    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr,
                                                 nullptr, nullptr);
    if (!png_ptr)
    {
        fclose(fp);
        throw std::runtime_error{"Failed to create libpng read struct"};
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr)
    {
        png_destroy_read_struct(&png_ptr, nullptr, nullptr);
        fclose(fp);
        throw std::runtime_error{"Failed to create libpng info struct"};
    }

    // set error handling to not abort the entire program
    if (setjmp(png_jmpbuf(png_ptr)))
    {
        png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
        fclose(fp);
        throw std::runtime_error{"Error reading png metadata"};
    }

    // initialize png reading
    png_init_io(png_ptr, fp);
    // let it know we've already read the first 8 bytes
    png_set_sig_bytes(png_ptr, 8);

    // read in the basic image info
    png_read_info(png_ptr, info_ptr);

    // convert to 8 bits
    png_byte bit_depth = png_get_bit_depth(png_ptr, info_ptr);
    if (bit_depth == 16)
        png_set_strip_16(png_ptr);

    // verify this is in RGBA format, and if not, convert it to RGBA
    png_byte color_type = png_get_color_type(png_ptr, info_ptr);
    if (color_type != PNG_COLOR_TYPE_RGBA && color_type != PNG_COLOR_TYPE_RGB)
    {
        if (color_type == PNG_COLOR_TYPE_GRAY || color_type
                                                 == PNG_COLOR_TYPE_GRAY_ALPHA)
        {
            if (bit_depth < 8)
                png_set_expand(png_ptr);
            png_set_gray_to_rgb(png_ptr);
        }
        if (color_type == PNG_COLOR_TYPE_PALETTE)
            png_set_palette_to_rgb(png_ptr);
    }
    // convert tRNS to alpha channel
    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
        png_set_tRNS_to_alpha(png_ptr);

    size_t width = png_get_image_width(png_ptr, info_ptr);
    size_t height = png_get_image_height(png_ptr, info_ptr);
    rgba_pixel* newpix = nullptr;
    png_byte* row = nullptr;

    png_read_update_info(png_ptr, info_ptr);

    // begin reading in the image
    if (setjmp(png_jmpbuf(png_ptr)))
    {
        delete[] newpix;
        delete[] row;
        png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
        fclose(fp);
        throw std::runtime_error{"Error reading image with libpng"};
    }

    int bpr = png_get_rowbytes(png_ptr, info_ptr); // number of bytes in a row

    // initialize our image storage
    newpix = new rgba_pixel[height * width];
    row = new png_byte[bpr];

//.........这里部分代码省略.........

uint32_t * load_png(struct load_image *args)
{
	png_structp png;
	png_infop info;
	int color_type;
	void *rgb_data;
	png_bytep *pointers;
	int i;
	png_uint_32 w,h;
	int depth;
	struct png_context context;
	png_uint_32 stride;
	
	if(png_sig_cmp(args->data, 0, 8)) {
		DEBUG_PUTS("not png");
		return 0;
	}
	png = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
	info = png_create_info_struct(png);
	context.data = args->data;
	context.len = args->length;
	context.pos = 8;
	png_set_read_fn(png, &context, &read_callback);
	png_set_sig_bytes(png, 8);
	png_read_info(png, info);
	png_get_IHDR(png, info, &w, &h, &depth, &color_type, 0, 0, 0);
	DEBUG_PRINTF("w: %d\n", w);
	DEBUG_PRINTF("h: %d\n", h);
	switch (color_type) {
		case PNG_COLOR_TYPE_PALETTE:
		DEBUG_PUTS("pallete");
		png_set_palette_to_rgb(png);
		break;
		case PNG_COLOR_TYPE_RGB_ALPHA:
		DEBUG_PUTS("rgba");
		break;
		default:
		rgb_data = 0;
		goto out;
	};
	png_set_filler(png, 0xff, PNG_FILLER_AFTER);
	pointers = (png_bytep *) malloc(h * sizeof(*pointers));
	if (!pointers) {
		rgb_data = 0;
		goto out;
	}
	stride = png_get_rowbytes(png, info);
	rgb_data = malloc(stride * 4 * h);
	if (!rgb_data) {
		rgb_data = 0;
		goto out;
	}
	for (i = 0; i < h; i++)
		pointers[i] = rgb_data + w * 4 * i;
	png_read_image(png, pointers);
	*args->w = w;
	*args->h = h;
out:
	png_destroy_read_struct(&png, &info, 0);
	
	return rgb_data;
}

/* return -2 if file cannot be opened
 * return -1 if file data is corrupted
 * return  0 if file format is not valid
 * return  1 if file successfully loaded
 */
int read_image_file_png (const char* filename, ImageData *imagedata)
{
    int i, width, height, BPP;
    unsigned char* pixelArray = NULL;
    png_bytep* row_pointers;
    png_byte color_type;
    png_infop info_ptr;
    png_structp png_ptr;
    png_byte header[8];
    FILE *fp;


    /* open file for reading-bytes */
    fp = fopen (filename, "rb");

    if(!fp) ABORT("Read Error: file '%s' could not be opened for reading.", filename, -2)

    /* Test if file type is png */
    /* 8 bytes is the maximum size that can be checked */
    if(fread(header, 1, 8, fp) != 8
    || png_sig_cmp(header, 0, 8))
        ABORT("Read Error: file '%s' is not recognized as a PNG file.", filename, 0)


    /* initialise - prepare for parsing */
    png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if(!png_ptr)
        ABORT("Read Error: file '%s' is corrupted. png_create_read_struct failed.", filename, -1)

    info_ptr = png_create_info_struct (png_ptr);
    if(!info_ptr)
        ABORT("Read Error: file '%s' is corrupted. png_create_info_struct failed.", filename, -1)

    if(setjmp(png_jmpbuf(png_ptr)))
        ABORT("Read Error: file '%s' is corrupted. setjmp(png_jmpbuf(png_ptr)) failed.", filename, -1)

    png_init_io (png_ptr, fp);
    png_set_sig_bytes (png_ptr, 8);
    png_read_info (png_ptr, info_ptr);


    /* ensure 3-byte colour depth */
    color_type = png_get_color_type (png_ptr, info_ptr);
    if(color_type == PNG_COLOR_TYPE_GRAY ||
        color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
          png_set_gray_to_rgb (png_ptr);

    /* ensure Alpha channel present */
    png_set_filler(png_ptr, 0xFF, PNG_FILLER_AFTER);

    /*png_get_bit_depth(png_ptr, info_ptr) = 8... why so? */
    height = png_get_image_height(png_ptr, info_ptr);
    width  = png_get_image_width (png_ptr, info_ptr);
    BPP    = 4;

    /* ensure BGRA and not ARGB */
    png_set_bgr(png_ptr);

    /* make libpng to handle expansion of the interlaced image */
    png_set_interlace_handling (png_ptr);

    /* reflect requested transformations */
    png_read_update_info (png_ptr, info_ptr);


    /* prepare to read file */
    if(setjmp(png_jmpbuf(png_ptr)))
        ABORT("Read Error: file '%s' is corrupted. setjmp(png_jmpbuf(png_ptr)) failed.", filename, -1)

    /* allocate memory needed to hold the image */
    pixelArray = (unsigned char*) malloc (height*width*BPP);

    row_pointers = (png_bytep*) malloc (height * sizeof(*row_pointers));

    for(i = 0; i < height; i++)
        row_pointers[i] = (png_bytep) (pixelArray + i*width*BPP);

    /* finally... read image file... */
    png_read_image(png_ptr, row_pointers);

    /* free resources */
    free(row_pointers);
    fclose(fp);


    /* success */
    imagedata->pixelArray = pixelArray;
    imagedata->height = height;
    imagedata->width = width;
    imagedata->bpp = BPP*8;
    return 1;
}

int res_create_surface_png(const char* name, gr_surface* pSurface) {
    GGLSurface* surface = NULL;
    int result = 0;
    unsigned char header[8];
    png_structp png_ptr = NULL;
    png_infop info_ptr = NULL;

    FILE* fp = fopen(name, "rb");
    if (fp == NULL) {
        char resPath[256];

        snprintf(resPath, sizeof(resPath)-1, "/res/images/%s.png", name);
        resPath[sizeof(resPath)-1] = '\0';
        fp = fopen(resPath, "rb");
        if (fp == NULL)
        {
            result = -1;
            goto exit;
        }
    }

    size_t bytesRead = fread(header, 1, sizeof(header), fp);
    if (bytesRead != sizeof(header)) {
        result = -2;
        goto exit;
    }

    if (png_sig_cmp(header, 0, sizeof(header))) {
        result = -3;
        goto exit;
    }

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr) {
        result = -4;
        goto exit;
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        result = -5;
        goto exit;
    }

    if (setjmp(png_jmpbuf(png_ptr))) {
        result = -6;
        goto exit;
    }

    png_set_packing(png_ptr);

    png_init_io(png_ptr, fp);
    png_set_sig_bytes(png_ptr, sizeof(header));
    png_read_info(png_ptr, info_ptr);

    size_t width = info_ptr->width;
    size_t height = info_ptr->height;
    size_t stride = 4 * width;
    size_t pixelSize = stride * height;

    int color_type = info_ptr->color_type;
    int bit_depth = info_ptr->bit_depth;
    int channels = info_ptr->channels;
    if (!(bit_depth == 8 &&
          ((channels == 3 && color_type == PNG_COLOR_TYPE_RGB) ||
           (channels == 4 && color_type == PNG_COLOR_TYPE_RGBA) ||
           (channels == 1 && color_type == PNG_COLOR_TYPE_PALETTE)))) {
        return -7;
        goto exit;
    }

    surface = malloc(sizeof(GGLSurface) + pixelSize);
    if (surface == NULL) {
        result = -8;
        goto exit;
    }
    unsigned char* pData = (unsigned char*) (surface + 1);
    surface->version = sizeof(GGLSurface);
    surface->width = width;
    surface->height = height;
    surface->stride = width; /* Yes, pixels, not bytes */
    surface->data = pData;
    surface->format = (channels == 3) ?
            GGL_PIXEL_FORMAT_RGBX_8888 : GGL_PIXEL_FORMAT_RGBA_8888;

    if (color_type == PNG_COLOR_TYPE_PALETTE) {
        png_set_palette_to_rgb(png_ptr);
    }

    int x;
    size_t y;
    if (channels == 3) {
        for (y = 0; y < height; ++y) {
            unsigned char* pRow = pData + y * stride;
            png_read_row(png_ptr, pRow, NULL);

            for(x = width - 1; x >= 0; x--) {
                int sx = x * 3;
                int dx = x * 4;
                unsigned char r = pRow[sx];
//.........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(info_ptr->bit_depth > 8) {
		XLOG(0, "warning: bit depth per channel is greater than 8 (%d). Attempting to strip, but image quality will be degraded.\n", info_ptr->bit_depth);
	}
	
	if(info_ptr->color_type == PNG_COLOR_TYPE_GRAY || info_ptr->color_type == PNG_COLOR_TYPE_RGB) {
		XLOG(0, "notice: attempting to add dummy transparency channel\n");
	}
	
	if(info_ptr->color_type == 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(info_ptr->width > 320 || info_ptr->height > 480) {
		XLOG(0, "error: dimensions out of range, must be within 320x480, not %lux%lu\n", info_ptr->width, info_ptr->height);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		return NULL;
	}

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

	if(info_ptr->color_type != PNG_COLOR_TYPE_GRAY_ALPHA && info_ptr->color_type != PNG_COLOR_TYPE_RGB_ALPHA) {
		XLOG(0, "error: incorrect color type, must be greyscale with alpha, or rgb with alpha\n");
		if(info_ptr->color_type == PNG_COLOR_TYPE_GRAY || info_ptr->color_type == PNG_COLOR_TYPE_RGB) {
			XLOG(0, "It appears you're missing an alpha channel. Add transparency to your image\n");
		}
		if(info_ptr->color_type == 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) * info_ptr->height);
	imageBuffer = malloc(info_ptr->height * info_ptr->rowbytes);
	for(i = 0; i < info_ptr->height; i++) {
		row_pointers[i] = imageBuffer + (info_ptr->rowbytes * i);
	}

//.........这里部分代码省略.........

// load in the image data
IImage* CImageLoaderPng::loadImage(io::IReadFile* file) const
{
#ifdef _IRR_COMPILE_WITH_LIBPNG_
	if (!file)
		return 0;

	video::IImage* image = 0;
	//Used to point to image rows
	u8** RowPointers = 0;

	png_byte buffer[8];
	// Read the first few bytes of the PNG file
	if( file->read(buffer, 8) != 8 )
	{
		os::Printer::log("LOAD PNG: can't read file\n", file->getFileName(), ELL_ERROR);
		return 0;
	}

	// Check if it really is a PNG file
	if( png_sig_cmp(buffer, 0, 8) )
	{
		os::Printer::log("LOAD PNG: not really a png\n", file->getFileName(), ELL_ERROR);
		return 0;
	}

	// Allocate the png read struct
	png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
		NULL, (png_error_ptr)png_cpexcept_error, NULL);
	if (!png_ptr)
	{
		os::Printer::log("LOAD PNG: Internal PNG create read struct failure\n", file->getFileName(), ELL_ERROR);
		return 0;
	}

	// Allocate the png info struct
	png_infop info_ptr = png_create_info_struct(png_ptr);
	if (!info_ptr)
	{
		os::Printer::log("LOAD PNG: Internal PNG create info struct failure\n", file->getFileName(), ELL_ERROR);
		png_destroy_read_struct(&png_ptr, NULL, NULL);
		return 0;
	}

	// for proper error handling
	if (setjmp(png_jmpbuf(png_ptr)))
	{
		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
		if (RowPointers)
			delete [] RowPointers;
		return 0;
	}

	// changed by zola so we don't need to have public FILE pointers
	png_set_read_fn(png_ptr, file, user_read_data_fcn);

	png_set_sig_bytes(png_ptr, 8); // Tell png that we read the signature

	png_read_info(png_ptr, info_ptr); // Read the info section of the png file

	u32 Width;
	u32 Height;
	s32 BitDepth;
	s32 ColorType;
	{
		// Use temporary variables to avoid passing casted pointers
		png_uint_32 w,h;
		// Extract info
		png_get_IHDR(png_ptr, info_ptr,
			&w, &h,
			&BitDepth, &ColorType, NULL, NULL, NULL);
		Width=w;
		Height=h;
	}

	// Convert palette color to true color
	if (ColorType==PNG_COLOR_TYPE_PALETTE)
		png_set_palette_to_rgb(png_ptr);

	// Convert low bit colors to 8 bit colors
	if (BitDepth < 8)
	{
		if (ColorType==PNG_COLOR_TYPE_GRAY || ColorType==PNG_COLOR_TYPE_GRAY_ALPHA)
#if (PNG_LIBPNG_VER_MAJOR > 1) || (PNG_LIBPNG_VER_MINOR > 3)
			png_set_expand_gray_1_2_4_to_8(png_ptr);
#else
			png_set_gray_1_2_4_to_8(png_ptr);
#endif
		else
			png_set_packing(png_ptr);
	}

GLuint png_texture_load(const char * file_name, int  width, int  height)
{
    png_uint_32 temp_width, temp_height;
    int bit_depth, color_type, i;

    png_byte header[8];
    GLuint texture;

    FILE *fp = fopen(file_name, "rb");
    if (fp == 0)
    {
        perror(file_name);
        return 0;
    }

    // read the header
    fread(header, 1, 8, fp);

    if (png_sig_cmp(header, 0, 8))
    {
        fprintf(stderr, "error: %s is not a PNG.\n", file_name);
        fclose(fp);
        return 0;
    }

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png_ptr)
    {
        fprintf(stderr, "error: png_create_read_struct returned 0.\n");
        fclose(fp);
        return 0;
    }

    // create png info struct
    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr)
    {
        fprintf(stderr, "error: png_create_info_struct returned 0.\n");
        png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
        fclose(fp);
        return 0;
    }

    // create png info struct
    end_info = png_create_info_struct(png_ptr);
    if (!end_info)
    {
        fprintf(stderr, "error: png_create_info_struct returned 0.\n");
        png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp) NULL);
        fclose(fp);
        return 0;
    }

    // the code in this if statement gets called if libpng encounters an error
    if (setjmp(png_jmpbuf(png_ptr))) {
        fprintf(stderr, "error from libpng\n");
        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
        fclose(fp);
        return 0;
    }

    // init png reading
    png_init_io(png_ptr, fp);

    // let libpng know you already read the first 8 bytes
    png_set_sig_bytes(png_ptr, 8);

    // read all the info up to the image data
    png_read_info(png_ptr, info_ptr);

    // variables to pass to get info



    // get info about png
    png_get_IHDR(png_ptr, info_ptr, &temp_width, &temp_height, &bit_depth, &color_type, NULL, NULL, NULL);

#if 0
    if (width ) {
        width = temp_width;
    }
    if (height ) {
        height = temp_height;
    }
#endif
    // Update the png info struct.
    png_read_update_info(png_ptr, info_ptr);

    // Row size in bytes.
    rowbytes = png_get_rowbytes(png_ptr, info_ptr);

    // glTexImage2d requires rows to be 4-byte aligned
    rowbytes += 3 - ((rowbytes-1) % 4);

    // Allocate the image_data as a big block, to be given to opengl

    image_data = (png_byte*)malloc(rowbytes * temp_height * sizeof(png_byte)+15);
    if (image_data == NULL)
    {
        fprintf(stderr, "error: could not allocate memory for PNG image data\n");
//.........这里部分代码省略.........

GLuint read_png_file(char* file_name)
{

    unsigned char header[8];    // 8 is the maximum size that can be checked

    /* open file and test for it being a png */
    FILE *fp = fopen(file_name, "rb");
    if (!fp)
        abort_("[read_png_file] File %s could not be opened for reading", file_name);

    fread(header, 1, 8, fp);
    if (png_sig_cmp(header, 0, 8))
        abort_("[read_png_file] File %s is not recognized as a PNG file", file_name);

    /* initialize stuff */
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);

    if (!png_ptr)
        abort_("[read_png_file] png_create_read_struct failed");

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr)
        abort_("[read_png_file] png_create_info_struct failed");


    end_info = png_create_info_struct(png_ptr);
    if (!end_info)
        abort_("[read_png_file] png_create_end_info_struct failed");


    if (setjmp(png_jmpbuf(png_ptr)))
        abort_("[read_png_file] Error during init_io");


    png_init_io(png_ptr, fp);
    png_set_sig_bytes(png_ptr, 8);

    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);
    color_type = png_get_color_type(png_ptr, info_ptr);
    bit_depth = png_get_bit_depth(png_ptr, info_ptr);

    number_of_passes = png_set_interlace_handling(png_ptr);

    png_read_update_info(png_ptr, info_ptr);

    // Row size in bytes.
    rowbytes = png_get_rowbytes(png_ptr, info_ptr);

    // glTexImage2d requires rows to be 4-byte aligned
    rowbytes += 3 - ((rowbytes-1) % 4);

    // Allocate the image_data as a big block, to be given to opengl

    image_data = (png_byte*)malloc(rowbytes * height * sizeof(png_byte)+15);
    if (image_data == NULL)
        abort_("[read_png_file] png_create_end_info_struct failed");

    if (setjmp(png_jmpbuf(png_ptr)))
        abort_("[read_png_file] Error during read_image");


    row_pointers = (png_bytep*) malloc(sizeof(png_bytep) * height);

    if (bit_depth == 16)
        rowbytes = width*8;
    else
        rowbytes = width*4;

    for (y=0; y<height; y++)
        row_pointers[y] = (png_byte*) malloc(rowbytes);

    png_read_image(png_ptr, row_pointers);


    glGenTextures(1, &Texture);
    glBindTexture(GL_TEXTURE_2D, Texture);
    glTexImage2D(GL_TEXTURE_2D,0, GL_RGB, width, height, 0,
                 GL_RGB, GL_UNSIGNED_BYTE, (GLvoid*) image_data );
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    // clean up
    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
    free(image_data);
    free(row_pointers);
    fclose(fp);
    return Texture;
}

ImageNode *LoadPNGImage(const char *fileName)
{

   static ImageNode *result;
   static FILE *fd;
   static unsigned char **rows;
   static png_structp pngData;
   static png_infop pngInfo;
   static png_infop pngEndInfo;

   unsigned char header[8];
   unsigned long rowBytes;
   int bitDepth, colorType;
   unsigned int x, y;
   png_uint_32 width;
   png_uint_32 height;

   Assert(fileName);

   result = NULL;
   fd = NULL;
   rows = NULL;
   pngData = NULL;
   pngInfo = NULL;
   pngEndInfo = NULL;

   fd = fopen(fileName, "rb");
   if(!fd) {
      return NULL;
   }

   x = fread(header, 1, sizeof(header), fd);
   if(x != sizeof(header) || png_sig_cmp(header, 0, sizeof(header))) {
      fclose(fd);
      return NULL;
   }

   pngData = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
   if(JUNLIKELY(!pngData)) {
      fclose(fd);
      Warning(_("could not create read struct for PNG image: %s"), fileName);
      return NULL;
   }

   if(JUNLIKELY(setjmp(png_jmpbuf(pngData)))) {
      png_destroy_read_struct(&pngData, &pngInfo, &pngEndInfo);
      if(fd) {
         fclose(fd);
      }
      if(rows) {
         ReleaseStack(rows);
      }
      DestroyImage(result);
      Warning(_("error reading PNG image: %s"), fileName);
      return NULL;
   }

   pngInfo = png_create_info_struct(pngData);
   if(JUNLIKELY(!pngInfo)) {
      png_destroy_read_struct(&pngData, NULL, NULL);
      fclose(fd);
      Warning(_("could not create info struct for PNG image: %s"), fileName);
      return NULL;
   }

   pngEndInfo = png_create_info_struct(pngData);
   if(JUNLIKELY(!pngEndInfo)) {
      png_destroy_read_struct(&pngData, &pngInfo, NULL);
      fclose(fd);
      Warning("could not create end info struct for PNG image: %s", fileName);
      return NULL;
   }

   png_init_io(pngData, fd);
   png_set_sig_bytes(pngData, sizeof(header));

   png_read_info(pngData, pngInfo);

   png_get_IHDR(pngData, pngInfo, &width, &height,
                &bitDepth, &colorType, NULL, NULL, NULL);
   result = CreateImage(width, height, 0);

   png_set_expand(pngData);

   if(bitDepth == 16) {
      png_set_strip_16(pngData);
   } else if(bitDepth < 8) {
      png_set_packing(pngData);
   }

   png_set_swap_alpha(pngData);
   png_set_filler(pngData, 0xFF, PNG_FILLER_BEFORE);

   if(colorType == PNG_COLOR_TYPE_GRAY
      || colorType == PNG_COLOR_TYPE_GRAY_ALPHA) {
      png_set_gray_to_rgb(pngData);
   }

   png_read_update_info(pngData, pngInfo);

//.........这里部分代码省略.........

static void read_png_file_low(const char* file_name, png_image_data_t *png_image_data)
{
    png_structp png_ptr;
    int number_of_passes;
	char header[8];	// 8 is the maximum size that can be checked
    int y;

	/* open file and test for it being a png */
	FILE *fp = fopen(file_name, "rb");
	if (!fp)
		abort_("[read_png_file] File %s could not be opened for reading", file_name);
	fread(header, 1, 8, fp);
	if (png_sig_cmp(header, 0, 8))
		abort_("[read_png_file] File %s is not recognized as a PNG file", file_name);


	/* initialize stuff */
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	
	if (!png_ptr)
		abort_("[read_png_file] png_create_read_struct failed");

	png_image_data->info_ptr = png_create_info_struct(png_ptr);
	if (!png_image_data->info_ptr)
		abort_("[read_png_file] png_create_info_struct failed");

	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during init_io");
	png_init_io(png_ptr, fp);

	png_set_sig_bytes(png_ptr, 8); /* 8 == sig_read ? */

	png_read_info(png_ptr, png_image_data->info_ptr);

    /* set transformations */
/*
	if ((png_image_data->info_ptr->color_type & PNG_COLOR_TYPE_RGB) == 0)
        transforms |= PNG_TRANSFORM_BGR;
*/
   if (png_get_valid(png_ptr, png_image_data->info_ptr, PNG_INFO_sBIT))
   {
      png_color_8p sig_bit;

      png_get_sBIT(png_ptr, png_image_data->info_ptr, &sig_bit);
      printf("sig_bit: %d\n", sig_bit);
      png_set_shift(png_ptr, sig_bit);
   }

    /* TODO DFG: is this needed? */
	number_of_passes = png_set_interlace_handling(png_ptr);
	png_read_update_info(png_ptr, png_image_data->info_ptr);





	/* read file */
	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during read_image");

#if 1
	png_image_data->row_pointers = (png_bytep*) qemu_malloc(sizeof(png_bytep) * png_image_data->info_ptr->height);
	for (y=0; y < png_image_data->info_ptr->height; y++)
		png_image_data->row_pointers[y] = (png_byte*) qemu_malloc(png_image_data->info_ptr->rowbytes);

	png_read_image(png_ptr, png_image_data->row_pointers);
#endif
    /* DFG TODO: Cleanup */

/*    png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); */

    fclose(fp);
}

static void read_png_file(const char* file_name, png_image_data_t *png_image_data, int max_width, int max_height)
{
    png_structp png_ptr;
    png_infop info_ptr;
    png_bytep *row_pointers;
	char header[8];	// 8 is the maximum size that can be checked
    int y;
    char* dest;

	/* open file and test for it being a png */
	FILE *fp = fopen(file_name, "rb");
	if (!fp)
		abort_("[read_png_file] File %s could not be opened for reading", file_name);
	fread(header, 1, 8, fp);
	if (png_sig_cmp(header, 0, 8))
		abort_("[read_png_file] File %s is not recognized as a PNG file", file_name);


	/* initialize stuff */
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	
	if (!png_ptr)
		abort_("[read_png_file] png_create_read_struct failed");

    if (max_width > 0 && max_height > 0)
        png_set_user_limits(png_ptr, max_width, max_height);

	info_ptr = png_create_info_struct(png_ptr);

	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during init_io");
	png_init_io(png_ptr, fp);

	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during init_io");
   png_set_sig_bytes(png_ptr, sizeof(header));

	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during init_io");
   png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_STRIP_ALPHA, png_voidp_NULL);

	if (setjmp(png_jmpbuf(png_ptr)))
		abort_("[read_png_file] Error during init_io");

    row_pointers = png_get_rows(png_ptr, info_ptr);

    png_image_data->height = png_get_image_height(png_ptr, info_ptr);
    png_image_data->width = png_get_image_width(png_ptr, info_ptr);

    png_image_data->image4c = (void*)qemu_malloc(png_image_data->width * png_image_data->height * 4);

    dest = (char*)png_image_data->image4c;

    /* transform this from 3 channels to a (fake for now) 4 channels */
	for (y=0; y < png_image_data->height; y++) {
        char* src = row_pointers[y];
        int x;
        for (x = 0; x < png_image_data->width; x++) {
            *dest = *src; dest++, src++;
            *dest = *src; dest++, src++;
            *dest = *src; dest++, src++;
            *dest = 0; dest++; /* alpha channel ignored */ 
        }
    }

    png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);

    fclose(fp);
}

/* Read the information before the actual image data.  This has been
 * changed in v0.90 to allow reading a file that already has the magic
 * bytes read from the stream.  You can tell libpng how many bytes have
 * been read from the beginning of the stream (up to the maximum of 8)
 * via png_set_sig_bytes(), and we will only check the remaining bytes
 * here.  The application can then have access to the signature bytes we
 * read if it is determined that this isn't a valid PNG file.
 */
void PNGAPI
png_read_info(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_info\n");
   /* save jump buffer and error functions */
   /* If we haven't checked all of the PNG signature bytes, do so now. */
   if (png_ptr->sig_bytes < 8)
   {
      png_size_t num_checked = png_ptr->sig_bytes,
                 num_to_check = 8 - num_checked;

      png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
      png_ptr->sig_bytes = 8;

      if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
      {
         if (num_checked < 4 &&
             png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
            png_error(png_ptr, "Not a PNG file");
         else
            png_error(png_ptr, "PNG file corrupted by ASCII conversion");
      }
      if (num_checked < 3)
         png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
   }

   for(;;)
   {
#ifdef PNG_USE_LOCAL_ARRAYS
      PNG_IHDR;
      PNG_IDAT;
      PNG_IEND;
      PNG_PLTE;
#if defined(PNG_READ_bKGD_SUPPORTED)
      PNG_bKGD;
#endif
#if defined(PNG_READ_cHRM_SUPPORTED)
      PNG_cHRM;
#endif
#if defined(PNG_READ_gAMA_SUPPORTED)
      PNG_gAMA;
#endif
#if defined(PNG_READ_hIST_SUPPORTED)
      PNG_hIST;
#endif
#if defined(PNG_READ_iCCP_SUPPORTED)
      PNG_iCCP;
#endif
#if defined(PNG_READ_iTXt_SUPPORTED)
      PNG_iTXt;
#endif
#if defined(PNG_READ_oFFs_SUPPORTED)
      PNG_oFFs;
#endif
#if defined(PNG_READ_pCAL_SUPPORTED)
      PNG_pCAL;
#endif
#if defined(PNG_READ_pHYs_SUPPORTED)
      PNG_pHYs;
#endif
#if defined(PNG_READ_sBIT_SUPPORTED)
      PNG_sBIT;
#endif
#if defined(PNG_READ_sCAL_SUPPORTED)
      PNG_sCAL;
#endif
#if defined(PNG_READ_sPLT_SUPPORTED)
      PNG_sPLT;
#endif
#if defined(PNG_READ_sRGB_SUPPORTED)
      PNG_sRGB;
#endif
#if defined(PNG_READ_tEXt_SUPPORTED)
      PNG_tEXt;
#endif
#if defined(PNG_READ_tIME_SUPPORTED)
      PNG_tIME;
#endif
#if defined(PNG_READ_tRNS_SUPPORTED)
      PNG_tRNS;
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
      PNG_zTXt;
#endif
#endif /* PNG_GLOBAL_ARRAYS */
      png_byte chunk_length[4];
      png_uint_32 length;

      png_read_data(png_ptr, chunk_length, 4);
      length = png_get_uint_32(chunk_length);

      png_reset_crc(png_ptr);
//.........这里部分代码省略.........

static int
lload(lua_State *L) {
    int top = lua_gettop(L);
    FILE *fp; 
    struct png_source source;
    if (top == 1) {
        const char *filename = luaL_checkstring(L,1);
        fp = fopen(filename, "rb");
        if (fp == NULL) {
            return luaL_error(L, strerror(errno));
        }
        unsigned char header[PNGSIGSIZE];
        if (fread(header, 1, PNGSIGSIZE, fp) != PNGSIGSIZE) {
            return luaL_error(L, "png invalid");
        }
        if (png_sig_cmp(header, 0, PNGSIGSIZE)) {
            return luaL_error(L, "png sig invalid");
        }
        fseek(fp, 0, SEEK_SET);
    } else if (top == 2) {
        luaL_checktype(L,1,LUA_TLIGHTUSERDATA);
        void *data = lua_touserdata(L,1);
        size_t size = luaL_checkinteger(L,2);
        if (size < PNGSIGSIZE) {
            return luaL_error(L, "png invalid");
        }
        if (png_sig_cmp(data, 0, PNGSIGSIZE)) {
            return luaL_error(L, "png sig invalid");
        }
        source.data = data;
        source.size = size;
        source.offset = 0;
    } else {
        return luaL_error(L, "invalid argument number");
    }
    
    png_structp png_ptr;
    png_infop info_ptr;
    png_uint_32 width, height;
    int bit_depth, color_type, interlace_type;
    int step;//, type;

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (png_ptr == NULL) {
        return 0;
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (info_ptr == NULL) {
        png_destroy_read_struct(&png_ptr, NULL, NULL);
        return 0;
    }

    if (setjmp(png_jmpbuf(png_ptr))) {
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        return 0;
    }

    if (top == 1)
        png_init_io(png_ptr, fp);
    else
        png_set_read_fn(png_ptr, (void *)&source, png_read_cb);

    //png_set_sig_bytes(png_ptr, PNGSIGSIZE);

    png_read_info(png_ptr, info_ptr);

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

    if (color_type == PNG_COLOR_TYPE_PALETTE)
        png_set_palette_to_rgb(png_ptr);

    if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
        bit_depth = 8;
        png_set_expand_gray_1_2_4_to_8(png_ptr);
    }

    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) != 0)
        png_set_tRNS_to_alpha(png_ptr);

    if (bit_depth == 16)
        png_set_strip_16(png_ptr);

    if (bit_depth < 8)
        png_set_packing(png_ptr);

    png_read_update_info(png_ptr, info_ptr);
    bit_depth = png_get_bit_depth(png_ptr, info_ptr);
    color_type = png_get_color_type(png_ptr, info_ptr);
    switch (color_type) {
    case PNG_COLOR_TYPE_GRAY:
        // type = TEXTURE_DEPTH;
        step = 1;
        break;
    case PNG_COLOR_TYPE_RGB:
        //type = TEXTURE_RGB;
        step = 3;
        break;
    case PNG_COLOR_TYPE_RGB_ALPHA:
//.........这里部分代码省略.........