Global NCC

Problem

Compute the normalized cross-correlation between two same-shaped images.

Subtract each image mean, then divide the dot product of the centered images by the product of their L2 norms. Return 0.0 when either image is constant, otherwise round to 4 decimal places.

Test cases

case 1

in: [[[1,2],[3,4]],[[1,2],[3,4]]]

expected: 1

case 2

in: [[[1,2],[3,4]],[[-1,-2],[-3,-4]]]

expected: -1

case 3

in: [[[1,2],[3,4]],[[7,7],[7,7]]]

expected: 0

case 4

in: [[[1,2],[3,4]],[[1,2],[3,5]]]

expected: 0.9827

Starter codePython

def global_ncc(a, b):
    # Your code here
    pass

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