message: Encode sRGB images as sRGB, not linear
  Fixes
diff: @@ -372,6 +372,8 @@ bool PNGEncoder::encode(const LinearImage& image) {
  data = fromLinearToRGBM<uint8_t>(image);
  break;
  case PixelFormat::sRGB:
  + data = fromLinearTosRGB<uint8_t>(image);
  + break;
  case PixelFormat::LINEAR_RGB:
  data = fromLinearToRGB<uint8_t>(image);
  break;
  