void webp_reader<T>::read(unsigned x0, unsigned y0,image_data_32& image)
{
WebPDecoderConfig config;
config_guard guard(config);
if (!WebPInitDecoderConfig(&config))
{
throw image_reader_exception("WEBP reader: WebPInitDecoderConfig failed");
}
config.options.use_cropping = 1;
config.options.crop_left = x0;
config.options.crop_top = y0;
config.options.crop_width = std::min(width_ - x0, image.width());
config.options.crop_height = std::min(height_ - y0, image.height());
if (WebPGetFeatures(buffer_->data(), buffer_->size(), &config.input) != VP8_STATUS_OK)
{
throw image_reader_exception("WEBP reader: WebPGetFeatures failed");
}
config.output.colorspace = MODE_RGBA;
config.output.u.RGBA.rgba = (uint8_t *)image.getBytes();
config.output.u.RGBA.stride = 4 * image.width();
config.output.u.RGBA.size = image.width() * image.height() * 4;
config.output.is_external_memory = 1;
if (WebPDecode(buffer_->data(), buffer_->size(), &config) != VP8_STATUS_OK)
{
throw image_reader_exception("WEBP reader: WebPDecode failed");
}
}
inline int import_image_data(image_data_32 const& im,
WebPPicture & pic,
bool alpha)
{
int stride = sizeof(image_data_32::pixel_type) * im.width();
if (alpha)
{
return WebPPictureImportRGBA(&pic, im.getBytes(), stride);
}
else
{
#if (WEBP_ENCODER_ABI_VERSION >> 8) >= 1
return WebPPictureImportRGBX(&pic, im.getBytes(), stride);
#else
return WebPPictureImportRGBA(&pic, im.getBytes(), stride);
#endif
}
}