addWeighted outputs incorrectly when any element in src2 is zero

[willSapgreen]

Expected behaviour

For each pixel, the output should follow
dst = src1 * alpha + src2 * beta + gamma

Actual behaviour

If a pixel's value in src2 is zero,
dst = src1

For example, given alpha = 0.5
src1 [110 126 239]
src2 [0 0 0]
dst [110 126 239]

Steps to reproduce

• example code

alpha = 0.5
beta = 1.0 - alpha
dst = cv2.addWeighted(src1, alpha, src2, beta, 0.0)

• operating system:
  Ubuntu 20.04.6 LTS

• architecture:
  x86

• opencv-python version:
  4.10.0

Issue submission checklist

• This is not a generic OpenCV usage question (looking for help for coding, other usage questions, homework etc.)
• I have read the README of this repository and understand that this repository provides only an automated build toolchain for OpenCV Python packages (there is no actual OpenCV code here)
• The issue is related to the build scripts in this repository, to the pre-built binaries or is a feature request (such as "please enable this additional dependency")
• I'm using the latest version of opencv-python

[asmorkalov]

Just tried current 4.x branch. It works well:

import cv2
import numpy as np

src1 = np.array([110, 126, 239], dtype=np.uint8)
src2 = np.array([0, 0, 0], dtype=np.uint8)

alpha = 0.5
beta = 1.0 - alpha
dst = cv2.addWeighted(src1, alpha, src2, beta, 0.0)
print(dst)

Output:

[[ 55]
 [ 63]
 [120]]