Python PIL overlay pixels with color while mantaining the lightness and shadows

Question

I had two scripts which I merged but 2 problems arised:

1. for light colors which are overlayed the result is way too bright as it overlays the original pixels that were brighter than others with total white rather than their color. For example "lightblue" "pink" and "grey". While the rest of the colors when overlayed the result is perfect

2. it won't process the png which first word is "2white" (3rd condition).

It seems like the color is getting overlayed just like the "Linear Dodge" blend mode in Photoshop, while what I want would be a "Overlay" blend mode.

I'd be very thankful if someone could help me one with this.

Here's the results for example:

Photo 4 and 5 would be the wanted result for lightblue and blue overlay.

Answer 1

Did you know that there's a Python package blend-modes to implement blend modes? I didn't, until I went searching. Since you edited the question to say you wanted the equivalent of Photoshop's Overlay mode, this became easy.

import blend_modes
import numpy as np
from PIL import Image

def overlay(im, color):
    ''' Takes a PIL.Image and RGB tuple as input,
        returns a PIL.Image of the result.
    '''
    im2 = np.array(im).astype(float)
    im3 = im2.copy()
    color_with_alpha = list(color) + [255] * (im3.shape[2]-len(color))
    color_array = np.array(color_with_alpha, dtype=float)
    im3[:,:] = color_array
    blended_img_float = blend_modes.overlay(im2, im3, 1.0)
    blended_img = np.uint8(blended_img_float)
    return Image.fromarray(blended_img)

And here's the result with your sample image and lightblue (99, 168, 231):