Blend one image with another using an alpha mask in python

alpha_mask_blend.py

import cv2
 
# Read the images
foreground = cv2.imread("puppets.png")
background = cv2.imread("ocean.png")
alpha = cv2.imread("puppets_alpha.png")
 
# Convert uint8 to float
foreground = foreground.astype(float)
background = background.astype(float)
 
# Normalize the alpha mask to keep intensity between 0 and 1
alpha = alpha.astype(float)/255
 
# Multiply the foreground with the alpha matte
foreground = cv2.multiply(alpha, foreground)

width      = background.shape[0]
height     = background.shape[1]
alpha_full                    = cv2.getStructuringElement(cv2.MORPH_RECT,(height,width))
alpha_full                    = 1.0 - alpha_full
foreground_full               = alpha_full
alpha_full[:alpha_w,:alpha_h] = alpha[:,:,0]


#Multiply the background with (1-alpha) 
for i in range(3):
    background[:,:,i]             = cv2.multiply(1.0 - alpha_full, background[:,:,i])
 
# Add the masked foreground and background.
outImage = background    
for i in range(3):  
    foreground_full[:alpha_w,:alpha_h] = foreground[:,:,i]
    outImage[:,:,i]                    = cv2.add(foreground_full, background[:,:,i])

 
# Display image
cv2.imshow("outImg", outImage/255)
cv2.waitKey(0)