UIImageToMat() retains data from previous calls - c++

Question

I am using OpenCV on iOS.
When I run the grabCut function below in a .mm file and supply:
a green "I" for inclStrokesImg
a red "E" for exclStrokesImg,
I expect to see a white "I" and "E" for inclStrokesDebug and exclStrokesDebug respectively, but now I am seeing
an "I" for `inclStrokesDebug" (expected)
but an "IE" for exclStrokesDebug (incorrect, expect to see E only)
cv::Mat cvt2Mask (UIImage * img) {
cv::Mat mask ;
if (img == nil){
return mask;
}
UIImageToMat(img, mask);
cv::cvtColor(mask, mask, CV_RGBA2GRAY);
cv::threshold(mask, mask, 1, 255, cv::THRESH_BINARY);
return mask;
}
+(UIImage *)grabCut:(UIImage *)srcImg withMask:(UIImage *)maskImg andInclusiveStrokes:(UIImage *)inclStrokesImg andExclusiveStrokes:(UIImage *)exclStrokesImg {
// Returns an inclusive mask image
cv::Mat src;
UIImageToMat(srcImg, src);
cv::Mat mask = cvt2Mask(maskImg);
cv::Mat inclStrokes = cvt2Mask(inclStrokesImg);
cv::Mat exclStrokes = cvt2Mask(exclStrokesImg);
#ifdef DEBUG
UIImage * maskDebug = MatToUIImage(mask);
UIImage * inclStrokesDebug = MatToUIImage(inclStrokes);
UIImage * exclStrokesDebug = MatToUIImage(exclStrokes);
#endif
...
return ...;
}
I checked the cvt2mask function, the UIImageToMat() went wrong and returned a result combined with previous results.
I ran the grabCut function again with the same parameters, the inclStrokesDebug will now return "IE" instead of "I" that I saw in the first call.
Is it due to some memory not released issues?

Answer 1

Problem seems fixed when I supply the alpha bool, for unknown reasons. I am using OpenCV 3.4.4
cv::Mat cvt2Mask (const UIImage * img) {
...
UIImageToMat(img, maskX, true);
...
return maskX;
}