String ImageBuffer::toDataURL(const String& mimeType, const double* quality) const
{
if (m_size.isEmpty())
return "data:,";
enum {
EncodeJPEG,
EncodePNG,
} encodeType = mimeType.lower() == "image/png" ? EncodePNG : EncodeJPEG;
// According to http://www.w3.org/TR/html5/the-canvas-element.html,
// "For image types that do not support an alpha channel, the image must be"
// "composited onto a solid black background using the source-over operator,"
// "and the resulting image must be the one used to create the data: URL."
// JPEG doesn't have alpha channel, so we need premultiplied data.
RefPtr<ImageData> imageData = encodeType == EncodePNG
? getUnmultipliedImageData(IntRect(IntPoint(0, 0), m_size))
: getPremultipliedImageData(IntRect(IntPoint(0, 0), m_size));
ASSERT(imageData && imageData->width() == m_size.width() && imageData->height() == m_size.height());
Vector<char> output;
const char* header;
if (encodeType == EncodePNG) {
if (!compressRGBABigEndianToPNG(imageData->data()->data()->data(), m_size, output))
return "data:,";
header = "data:image/png;base64,";
} else {
if (!compressRGBABigEndianToJPEG(imageData->data()->data()->data(), m_size, output))
return "data:,";
header = "data:image/jpeg;base64,";
}
Vector<char> base64;
base64Encode(output, base64);
output.clear();
Vector<char> url;
url.append(header, strlen(header));
url.append(base64);
return String(url.data(), url.size());
}
static bool encodeImageJPEG(unsigned char* data, IntSize size, Vector<char>* output, Optional<double> quality)
{
return compressRGBABigEndianToJPEG(data, size, *output, quality);
}
