Why is contours changing slightly allthough the object is still?

asked 2017-05-13 13:00:02 -0600

agroms
26 ●2 ●5

updated 2017-05-15 13:55:35 -0600

berak
32993 ●7 ●81 ●312

Hello, I have been working a lot with contours lately in different video programs. If I measure the contour of a object in realtime or video, and even though the camera and object is not moving at all and nothing is changed in regards to lighting, it seems like the contours are flickering and sometimes changed slightly. It is not more than maybe 1-2 pixel in change along the edge. My question is if there is any special reason for this? Is the program or my computer to slow to calculate exactly the same contour for each frame?

Thanks in advance for any explenation!

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answered 2017-05-13 13:18:29 -0600

matman
1001 ●6 ●16

updated 2017-05-13 13:44:14 -0600

That's because of camera noise. Depending on what you are doing bluring image slightly (GaussianBlur, boxBlur, medianBlur) can help. Contour calculation is always the same.

EDIT: medianBlur with kernel size 3 works good for salt-and-pepper noise.

EDIT2: Canny edge detection can jump between two pixels if the edge is very sharp in this case GaussianBlur might help.