OpenCV - locations of all non-zero pixels in binary image

Question

How can I find the locations of all non-zero pixels in a binary image (cv::Mat)? Do I have to scan through every pixel in the image or is there a high level OpenCV function(

Answer 1

Anyone looking to do this in python. it is also possible to do it with numpy arrays and therefore you don't need to upgrade your opencv version (or use undocumented functions).

mask = np.zeros(imgray.shape,np.uint8)
cv2.drawContours(mask,[cnt],0,255,-1)
pixelpoints = np.transpose(np.nonzero(mask))
#pixelpoints = cv2.findNonZero(mask)

Commented out is the same function using openCV instead. For more info see:

https://github.com/abidrahmank/OpenCV2-Python-Tutorials/blob/master/source/py_tutorials/py_imgproc/py_contours/py_contour_properties/py_contour_properties.rst