1. Prewitt edge detector: gradient filter and nonmaxima-suppression (NMS)

Output is two images: 1. gradient magnitute; 2. final result after NMS.

Input:

Prewitt edge detection:

Nonmaxima-suppression:

2. Thresholding algorithm by Otsu

Output: thresholded image and obtained threshold value.

Input:

Output:

3. Circle Hough Transform

Output: 1. accumulator image; 2. input image with objects detected in given range of diameters

Input:

Output: