Apply color vibrance adjustments

color_vibrance.py

# Copy from https://github.com/bbonik/image_enhancement/blob/f0c286a166443202d592b920b63ee6901a0ee727/source/image_enhancement.py#L1388

import numpy as np
from skimage import img_as_float

def change_color_saturation(
        image_color, 
        image_ph_mask=None, 
        sat_degree=1.5,):
    LOCAL_BOOST = 0.2
    THRESHOLD_DARK_TONES = 100 / 255
    
    #TODO: return the same image type
    image_color = img_as_float(image_color)  # [0,1]
    
    # define gray scale
    image_gray = (image_color[:,:,0] + 
                  image_color[:,:,1] + 
                  image_color[:,:,2]) / 3
    image_gray = np.dstack([image_gray] * 3)  # grayscale with 3 channels
    
    image_delta = image_color - image_gray  # deviations from gray
    
    # defining local color amplification degree
    if image_ph_mask is not None:
        detail_amplification_local = image_ph_mask / THRESHOLD_DARK_TONES
        detail_amplification_local[detail_amplification_local>1] = 1
        detail_amplification_local = ((1 - detail_amplification_local) * 
                                      LOCAL_BOOST) + 1  # [1, 1.2]
        detail_amplification_local = np.dstack(
                [detail_amplification_local] * 3)  # 3 channels
    else:
        detail_amplification_local = 1
    
    image_new_sat = (image_gray + 
                     image_delta * sat_degree * detail_amplification_local)
    
    image_new_sat = np.clip(
            a=image_new_sat, 
            a_min=0, 
            a_max=1, 
            out=image_new_sat
            )
    
    return image_new_sat