- Gaussian smoothing
- non-maximal suppression (thinning)
- threshold with hysteresis to connect edge point
Non-maximum suppression essentially locates the highest points in the edge magnitude data. This is performed by using edge direction information, to check that points are at the peak of a ridge.
Hysteresis thresholding: two thresholds (Low, High). Every value below L is set to 0, above H is set to 1. The rest of the pixels are set to 1 if they are 4(8)-way connected to any other 1-value point.