Image Entropy

Problem

Compute the Shannon entropy of a grayscale image in bits.

Build a 256-bin histogram, let p be each non-zero bin probability, then return round(-sum(p * log2(p)), 4). A constant image has entropy 0.0 and an empty image also returns 0.0.

Hint

Only non-zero histogram bins contribute to the sum of -p * log2(p).

Test cases

case 1

in: [[[0,0],[255,255]]]

expected: 1

case 2

in: [[[7,7],[7,7]]]

expected: 0

case 3

in: [[[0,1],[2,3]]]

expected: 2

case 4

in: [[[0,0,0,255]]]

expected: 0.8113

Starter codePython

def image_entropy(image):
    # Your code here
    pass

4 test cases · run your code against them in the editor