OpenCv4Android: frame masking by an image

Question

I want to mask each frame that I get from the camera and mask it by an image in Drawable folder. That is, I wan to find my region of interest in a MAT. How can I do that?

Answer 1

An image's (say mRgba as a landscape image from the camera) ROI is dictated by its dimensions, so:

Rect roi = new Rect(0,0,mRgba.width(), mRgba.height());

if you want to mask a particular part of the image then I'd suggest using submat, so if mRgba was the image from the camera you can set a ROI and then resize your drawable into that area. For example, to draw an image into the top left corner of your original image in a 100x100 square.

Rect subROI = new Rect(0,0,100,100);
Mat subimg = mRgba.submat(subROI);
Mat yourDrawable = ....
Imgproc.resize(yourDrawable, submig, submig.size());

As submig is a reference to the subROI the pixels in the top left area of mRgba will be updated.