Median Filter

Problem

Apply a median filter with a k x k window to a grayscale image.

At each valid position, sort the k * k window values and take the element at index (k * k) // 2 (the lower median). k is odd and the image has at least k rows and columns.

Hint

Collect all k * k values, sort them and pick the middle index.

Test cases

case 1

in: [[[1,1,1],[1,100,1],[1,1,1]],3]

expected: [[1]]

case 2

in: [[[5]],1]

expected: [[5]]

case 3

in: [[[9,2,8],[4,7,1],[3,6,5]],3]

expected: [[5]]

case 4

in: [[[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]],3]

expected: [[6,7],[10,11]]

Starter codePython

def median_filter(image, k):
    # Your code here
    pass

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