Question

UPDATE:

My original question here is not valid, sorry. I left a line out from it, where m.create gets called. If there was no answer on this I would delete the question right away.

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I’ve just noticed that Mat::adjustROI seems to change the wholeSize of cv::Mat.

Mat m(11,11,CV_32FC1);
Size wholeSize, old_size;
Point ofs;
m.locateROI(old_size, ofs);
m.adjustROI(0,old_size.height/2,0,old_size.width/2);
m.locateROI(wholeSize, ofs);
assert(wholeSize==old_size); // fails, wholeSize is now smaller

Is this normal?
If so, I suspect reallocation otherwise this could be a source of a memory leak.
If Im right, when does the reallocation occur?

Answer 1

I ran your code, and the assert doesn’t fail for me (MSVC 2010). I stepped through it with the debugger and I can also see in the watch window that both sizes are equal (x and y equal to 11). I’m a beginner in OpenCV, but from the documentation of the function it seems to me adjustROI should not modify “wholeSize”.

The method is complimentary to the cv::Mat::locateROI. Indeed, the
typical use of these functions is to determine the submatrix position
within the parent matrix and then shift the positionsomehow. Typically
it can be needed for filtering operations, when pixels outside of the
ROI shouldbe taken into account. When all the method’s parameters are
positive, it means that the ROI needsto grow in all directions by the
specified amount.