Applying a coloured overlay to an image in either PIL or Imagemagik

Question

I am a complete novice to image processing, and I am guessing this is quite easy to do, but I just don\'t know the terminology.

Basically, I have a black and white im

Answer 1

See my gist https://gist.github.com/Puriney/8f89b43d96ddcaf0f560150d2ff8297e

Core function via opencv is described as below.

def mask_color_img(img, mask, color=[0, 255, 255], alpha=0.3):
    '''
    img: cv2 image
    mask: bool or np.where
    color: BGR triplet [_, _, _]. Default: [0, 255, 255] is yellow.
    alpha: float [0, 1]. 

    Ref: http://www.pyimagesearch.com/2016/03/07/transparent-overlays-with-opencv/
    '''
    out = img.copy()
    img_layer = img.copy()
    img_layer[mask] = color
    out = cv2.addWeighted(img_layer, alpha, out, 1 - alpha, 0, out)
    return(out)

Add colored and transparent overlay on either RGB or gray image can work: