Divide an image into 5x5 blocks in python and compute histogram for each block

Question

Using Python, I have to:

• Divide a Test_Image and Reference_image into 5x5 blocks,
• Compute a histogram for each block, and

Answer 1

To divide a square image into square blocks (same number of blocks per axis), I used this method (full repository here):

def blockDivide(img, blockNumber):

    imgArray = np.array(Image.open(img))

    # Define dimension of image
    dimension = imgArray.shape[0]

    # Set number of slices per axis
    axisSlice = int(math.sqrt(blockNumber))

    # Size of each block
    arraySize = int(dimension / axisSlice)

    # Shape of numpy array to be filled
    blocksArray = np.zeros((arraySize, arraySize, blockNumber))

    # Split the image into vertical blocks
    split_a = np.split(imgArray, axisSlice, axis = 0)

    # Set counter to zero
    counter = 0

    for i in range(axisSlice):
        for j in range(axisSlice):

            # Split vertical blocks into square blocks
            split_b = np.split(split_a[i], axisSlice, axis = 1)

            # Fill array with blocks
            blocksArray[:, :, counter] = split_b[j]

            # Increase counter
            counter += 1

    return blocksArray