Detect and draw edges. The filter uses the Canny Edge Detection algorithm.

The filter accepts the following options:

low, high

Set low and high threshold values used by the Canny thresholding algorithm.

The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.

low and high threshold values must be choosen in the range [0,1], and low should be lesser or equal to high.

Default value for low is 20/255, and default value for high is 50/255.

Example:

edgedetect=low=0.1:high=0.4