message: BLOB - Support RGBA
diff: @@ -311,7 +311,7 @@ void SimpleBlobDetectorImpl::detect(InputArray image, std::vector<cv::KeyPoint>&
  //TODO: support mask
  keypoints.clear();
  Mat grayscaleImage;
  - if (image.channels() == 3)
  + if (image.channels() == 3 || image.channels() == 4)
  cvtColor(image, grayscaleImage, COLOR_BGR2GRAY);
  else
  grayscaleImage = image.getMat();
  