Gray-World Color Balance

Problem

Balance the colors of an RGB image with the gray-world assumption.

Compute the per-channel means, let target be their average, then scale each channel by target / mean, rounding to integers and clamping to [0, 255]. A channel whose mean is 0 is left unchanged.

Hint

Scale each channel so that all three channel means become equal.

Test cases

case 1

in: [[[[100,150,50]]]]

expected: [[[100,100,100]]]

case 2

in: [[[[200,100,0]]]]

expected: [[[100,100,0]]]

case 3

in: [[[[128,128,128]]]]

expected: [[[128,128,128]]]

Starter codePython

def gray_world(image):
    # Your code here
    pass

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