Thresholding is the assignment of each pixel in an image to either a true or false class based on the pixel's value, location or both. The result of a thresholding operation is typically a binary image in which each pixel is assigned either a true or false value. Some popular thresholding algorithms are: * median thresholding: pick a global threshold value that results in a final image as close as possible to 50% white, 50% black. * entropy thresholding: another way to pick a global threshold value * various "local thresholding" algorithms * ...