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)
 
# Multiply the background with ( 1 - alpha )
background = cv2.multiply(1.0 - alpha, background)
 
# Add the masked foreground and background.
outImage = cv2.add(foreground, background)
 
# Display image
cv2.imshow("outImg", outImage/255)
cv2.waitKey(0)

#This is a faster compositor
def composit(fg,bg,alpha):
'''
Composit fg image onto bg image according to alpha. Alpha should be float [0.0, 1.0]
uint8(fg * a + bg * (1-a))
:param fg: Foreground image, should be same shape as bg
:param bg: Background, should be same shape as fg
:param alpha: Alpha mask image 32FC1 [0.0 1.0] image same widthxheight as foreground
:return: 8U blended image
'''
a = (np.multiply(alpha, 1.0 / 255))[:,:,np.newaxis]
blended = cv2.convertScaleAbs(fg * a + bg * (1-a))
return blended

a = (np.multiply(alpha, 1.0 / 255))[:, :, np.newaxis]
IndexError: invalid index to scalar variable.

Hi,
Getting the following error for alpha_mask_blend.py. Please help.

error Traceback (most recent call last)
in ()
75
76 image = cv2.imread('E:\Python\Img-Seg\s2.jpg')
---> 77 decode_segmap('E:\Python\Img-Seg\s2.jpg')

in decode_segmap(source, nc)
63
64 # Multiply the foreground with the alpha matte
---> 65 foreground = cv2.multiply(a, foreground)
66
67 # Multiply the background with ( 1 - alpha )

error: OpenCV(3.4.1) C:\Miniconda3\conda-bld\opencv-suite_1533128839831\work\modules\core\src\arithm.cpp:659: error: (-209) The operation is neither 'array op array' (where arrays have the same size and the same number of channels), nor 'array op scalar', nor 'scalar op array' in function cv::arithm_op

And for garybradski reply:

ValueError Traceback (most recent call last)
in ()
75
76 image = cv2.imread('E:\Python\Img-Seg\s2.jpg')
---> 77 decode_segmap('E:\Python\Img-Seg\s2.jpg')

in decode_segmap(source, nc)
70 # Add the masked foreground and background
71 #outImage = cv2.add(foreground, background)
---> 72 blended = cv2.convertScaleAbs(foreground * a + background * (1-a))
73 # Return a normalized output image for display
74 return outImage/255

ValueError: operands could not be broadcast together with shapes (256,256,3,3) (256,256,1)

I get the same error as @Roopashaily . Has anyone resolved this?