Method decode

modules/engine/image_coder/src/image_coder_png.cpp:147–257

}

bool PNGImageDecoder::decode(EImageCoderColorFormat in_format, uint32_t in_bit_depth) SKR_NOEXCEPT
{
    SKR_ASSERT(initialized);
    const auto width = get_width();
    const auto height = get_height();
    const auto bit_depth = get_bit_depth();

    read_offset = 0;
    // create png read struct
    png_structp png_ptr	= png_create_read_struct_2(PNG_LIBPNG_VER_STRING, this, 
        PNGImageCoderHelper::user_error_fn, PNGImageCoderHelper::user_warning_fn, 
        NULL, PNGImageCoderHelper::user_malloc, PNGImageCoderHelper::user_free);
	png_infop info_ptr	= png_create_info_struct(png_ptr);
    png_bytep* row_pointers = (png_bytep*) png_malloc( png_ptr, height * sizeof(png_bytep) );
    SKR_DEFER({ png_free(png_ptr, row_pointers); png_destroy_read_struct(&png_ptr, &info_ptr, NULL); });
    if (setjmp(png_jmpbuf(png_ptr)) != 0)
    {
        return false;
    }
    if (png_color_type == PNG_COLOR_TYPE_PALETTE)
    {
        png_set_palette_to_rgb(png_ptr);
    }
    if ((png_color_type & PNG_COLOR_MASK_COLOR) == 0 && bit_depth < 8)
    {
        png_set_expand_gray_1_2_4_to_8(png_ptr);
    }
    // insert alpha channel if there is no alpha channel
    if ((png_color_type & PNG_COLOR_MASK_ALPHA) == 0 && (in_format == IMAGE_CODER_COLOR_FORMAT_RGBA || in_format == IMAGE_CODER_COLOR_FORMAT_BGRA))
    {
        // png images don't set PNG_COLOR_MASK_ALPHA if they have alpha from a tRNS chunk, but png_set_add_alpha seems to be safe regardless
        if ((png_color_type & PNG_COLOR_MASK_COLOR) == 0)
        {
            png_set_tRNS_to_alpha(png_ptr);
        }
        else if (png_color_type == PNG_COLOR_TYPE_PALETTE)
        {
            png_set_tRNS_to_alpha(png_ptr);
        }
        if (in_bit_depth == 8)
        {
            png_set_add_alpha(png_ptr, 0xff , PNG_FILLER_AFTER);
        }
        else if (in_bit_depth == 16)
        {
            png_set_add_alpha(png_ptr, 0xffff , PNG_FILLER_AFTER);
        }
    }
    // calculate pixel depth
    const uint64_t pixel_channels = (in_format == IMAGE_CODER_COLOR_FORMAT_Gray) ? 1 : 4;
    const uint64_t bytes_per_pixel = pixel_channels * in_bit_depth / 8;
    const uint64_t bytes_per_row = width * bytes_per_pixel;
    // reallocate raw data
    decoded_size = bytes_per_row * height;
    decoded_data = PNGImageDecoder::Allocate(decoded_size, get_alignment()); 
    // read png data
    png_set_read_fn(png_ptr, this, PNGImageCoderHelper::user_read_compressed);
    for (uint32_t i = 0; i < height; i++)