//std::cerr <<" Before = "<<(width * height * channels * sizeof *pixels)
// <<", after = "<<pngBufferSize << ", ratio = " << double(width * height * channels * sizeof *pixels)/pngBufferSize;
json.writeBase64(pngBuffer, pngBufferSize);
//std::cerr <<" Before = "<<(width * height * channels * sizeof *pixels)
// <<", after = "<<pngBufferSize << ", ratio = " << double(width * height * channels * sizeof *pixels)/pngBufferSize;
json.writeBase64(pngBuffer, pngBufferSize);