C++ (Cpp) PngFormat示例

示例#1

文件： image_io.cpp 项目： amarburg/Pangolin

TypedImage LoadPng(const std::string& filename)
{
    PANGOLIN_UNUSED(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_SWAP_ENDIAN, 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(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
}

示例#2

文件： image_io_png.cpp 项目： jiapei100/Pangolin

TypedImage LoadPng(std::istream& source)
{
#ifdef HAVE_PNG
    //so First, we validate our stream with the validate function I just mentioned
    if (!pango_png_validate(source)) {
        throw std::runtime_error("Not valid PNG header");
    }

    //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_set_read_fn(png_ptr,(png_voidp)&source, pango_png_stream_read);

    png_set_sig_bytes(png_ptr, PNGSIGSIZE);

    // Setup transformation options
    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);
    }

    //read the file
    png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_SWAP_ENDIAN, NULL);

    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(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);

    return img;
#else
    PANGOLIN_UNUSED(source);
    throw std::runtime_error("Rebuild Pangolin for PNG support.");
#endif // HAVE_PNG
}