This is a script for dividing the histogram of Grayscale image into N intervals ("shades of gray"), by the means of integral sums of the histogram.

####Idea: All intervals should have approximately equal integral sums.

####Input:

• img_fname -- Image filename
• N -- Wanted number of intervals

####Output:

• intervals -- array (of pairs) of shape (N, 2); each pair: [left_margin, right_margin]