res=cv2.add(img1, img2) 或者res=cv2.add(img1, 标量值)

import cv2

img1 = cv2.imread('1.jpg')
img2 = cv2.imread('2.jpg')
print(img1.shape)
print(img2.shape)
#输出： (1039, 750, 3)
   #(1050, 700, 3)
   
img2.resize((img1.shape[0],img1.shape[1],3))
print(img2.shape)
#输出：(1039, 750, 3)

res=cv2.add(img1,img2)#或者res=cv2.add(img1,10)

import cv2
import numpy as np

x = np.uint8([250])
y = np.uint8([10])

print( cv2.add(x,y) ) # 250+10 = 260 => 255
print( x+y )     # 250+10 = 260 % 256 = 4

cv2.addWeighted(src1, alpha, src2, beta, gamma[, dst[, dtype]]) → dst

import cv2
import numpy as np

img1 = cv2.imread('1.jpg')
img2 = cv2.imread('2.jpg')
#统一图片大小
img2 = cv2.resize(img2,(img1.shape[1],img1.shape[0]))

dst = cv2.addWeighted(img1,0.5,img2,0.5,0)

cv2.imshow('dst',dst)
cv2.waitKey(0)
cv2.destroyAllWindows()

'''
注意，src1和src2的形状要保持一致，一般都是同一张图像，
关键是在于mask，mask必须得是8-bit单通道array，尺寸也要和src相同
'''
bitwise_and(src1, src2[, dst[, mask]]) -> dst

import cv2
import numpy as np

img1 = cv2.imread('lena.jpg')
img2 = cv2.imread('opencv-logo-white.jpg')

# 把logo放在左上角，所以我们只关心这一块区域
rows, cols = img2.shape[:2]
roi = img1[:rows, :cols]

# 创建掩膜
img2gray = cv2.cvtColor(img2, cv2.COLOR_BGR2GRAY)
ret, mask = cv2.threshold(img2gray, 10, 255, cv2.THRESH_BINARY)
mask_inv = cv2.bitwise_not(mask)

# 保留除logo外的背景
img1_bg = cv2.bitwise_and(roi, roi, mask=mask_inv)
dst = cv2.add(img1_bg, img2) # 进行融合
img1[:rows, :cols] = dst # 融合后放在原图上

cv2.imshow('res',img1)
cv2.waitKey(0)
cv2.destroyAllWindows()