Contrast enhancer kernel

Sharpening can be done when contrast is enhanced.

This enhances edges and high-frequency details.

# Sharpen (= improve contrast)
kernel5 = np.array([[0, -1, 0], [-1, 5, -1], [0, -1, 0]])
image_conv5 = convolution(im_array, kernel5)
print(image_conv5.shape)