<It doesn’t work> sorry, what I meant was that the matrix forms but when you use it in warpPerspective() as outlined in the example on: OpenCV: Basic concepts of the homography explained with code (see c++ code) the resulting image gets created but seems to be blank (a white 600x600 image). i put a box below in the screenshot for where the image is to be displayed as a result of the warpPerspective() call.
here is a screenshot. just go to: iCollect and press ‘align’ then f12 (in chrome) to get dev tools and you can open the h-matrix and navigate through it.
