Canny Edge Operator

Primary edge detection steps:

1. Smoothing derivatives to suppress noise and compute gradient
2. Threshold to find regions of “significant” gradient.
3. “Thin” to get localized edge pixels
4. And link or connect edge pixels

Canny edge operator

1. Filter image with derivative of Gaussian
2. Find magnitude and orientation of gradient
3. Non-maximum suppression: Thin multi-pixel wide “ridges” down to single pixel width

4. Linking and thresholding (hysteresis):

5. Define two thresholds: low and high

6. Use the high threshold to start edge curves and the low threshold to continue them

MATLAB: edge(image, ‘canny’);