OpenCV mask mat needs to be of 8UC1 or 8SC1

Logic:

cameraframe -> mRGB mat (8UC4)
function(mRGB) returns mResult
show mResult if mResult != 0, otherwise, show mRGB.

In practice, this means I will need to create a mask mat, and mask mat needs to be 8UC1 or 8SC1.

Simply performing

mResult.convertTo(mMask, CvType.CV_8UC1)

does not work, as mMask will have a channel count of 4. One needs to:

mResult.convertTo(mMask, CvType.CV_8UC4) //or clone, or w/e Imgproc.cvtColor(mMask,mMask,Imgproc.COLOR_RGBA2GRAY)

and mMask will have a channel count of 1 and it can be used as a mat mask.