see also

[[openFrameworks]], [[Processing]]

Notes on findContours

  • Source image is modified by this function.
  • Also, the function does not take into account 1-pixel border of the image (it’s filled with 0’s and used for neighbor analysis in the algorithm), therefore the contours touching the image border will be clipped.

Subtract vs absdiff

Subtract can be useful instead of absdiff if you want only difference when something ‘appears or moves’ and not when it ‘disappears’

Optical Flow

  • use Farneback for a dense flow field,
  • use PyrLK for specific features




  • see also: [[cv]]
  • matrix set all values to 0: mat.setTo(0);
  • background subtraction:
  • [[openFrameworks]]