Scalar Median Filtering Strategy for Salt & Pepper Noise

ScalarMedianLexicalOrdering.py

def medianFilterLexicalOrdering(img, filterSize = 3):
    imgHeight, imWidth, channels = img.shape
    outputImg = np.zeros((imgHeight, imWidth, channels), dtype=np.uint8)

    filterHeight = filterWidth = filterSize
    filterEdge = filterWidth // 2

    for i in range(filterEdge, imgHeight - filterEdge):
        for j in range(filterEdge, imWidth - filterEdge):
            # retrieve a frame around the pixel i,j to check
            imgFilter = img[i - filterEdge : i + filterEdge + 1, j - filterEdge : j + filterEdge + 1].reshape(filterHeight * filterWidth, channels)

            # rotate the frame, lexically sort and get the indices of the order
            lexSortedIndexes = np.lexsort(np.rot90(imgFilter))

            # get the median index of the lexically sorted values, put its intensity
            outputImg[i][j] = imgFilter[lexSortedIndexes[(filterWidth * filterHeight // 2)]]

    return outputImg