Convert image to binary, black and white, by threshold.
The input image img can either be a grayscale or RGB image. In the later case, img is first converted to grayscale with
rgb2gray. Input can also be an indexed image X in which case the colormap cmap needs to be specified.
The value of threshold should be in the range [0,1] independently of the class of img. Values from other classes can be converted to the correct value with
im2doublefor example. For an automatic threshold, consider using
graythresh.bw = im2bw (img, graythresh (img));