Create a mask from a boundingRect in openCV

Question

Lets say I was given a boundingRect based on some points and stored it into a Rect object.

How can I use those points and create a mask in openCV? that is, everythin

Answer 1

Draw your rectangle with CV_FILLED option and invert it, like

Rect boundRect(x,y,W,H);
Mat mask(rows,cols,CV_8UC1,Scalar(0));
rectangle(mask,boundRect,Scalar(255),CV_FILLED,8,0);
bitwise_not(mask,mask);

or in another way without using invert, just create a white image and then draw rectangle using CV_FILLED option but with black color(Scalar(0)).

That is

Rect boundRect(x,y,W,H);
Mat mask(rows,cols,CV_8UC1,Scalar(255));
rectangle(mask,boundRect,Scalar(255),CV_FILLED,8,0);