Thresholding with Otsu and Riddler–Calvard

Thresholding refers to a family of algorithms that use a pixel value as a threshold to create a binary image (an image with only black-and-white pixels) from a grayscale image (this is the simplest possible method, segmenting foreground objects from the background in an image). The threshold can be chosen manually (by looking at the histogram of pixel values) or automatically using an algorithm. Image segmentation techniques may be noncontextual (without considering spatial relationships between the features in an image and grouping pixels only with regard to certain global attributes—for example, color/gray level) or contextual (additionally exploiting spatial relationships). In this recipe, you will learn how to use a couple of popular histogram-based thresholding methods known as Otsu's (with the assumption of a...