• canny—Finds edges in an image using Canny edge detection.

• freichen, prewitt, roberts, sobel—Finds edges in an image by convolving various kernels in sequence over an image matrix.

• compgrad, kirsch, robinson3, robinson5—Finds edges in an image convolving eight kernels in sequence over an image matrix and then comparing the results.

• rowgrad, colgrad—Finds horizontal or vertical edges in an image by detecting the row or column gradients of an image.