OpenCV-Python快速入门（三）：图像运算

前言

• 本文是个人快速入门OpenCV-Python的电子笔记，由于水平有限，难免出现错漏，敬请批评改正。
• 更多精彩内容，可点击进入
  OpenCV-Python快速入门专栏或我的个人主页查看

前提条件

• 熟悉Python

实验环境

• Python 3.x （面向对象的高级语言）
• OpenCV 4.0（python第三方库）pip3 install opencv-python

图像运算

加法运算”+“、add()

"+"运算

$$a+b=\{\begin{array}{l}a+b,a+b\le 255\\ (a+b)\%256,a+b>255\end{array}$$

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(5,5))
img2_resize=cv2.resize(img2,(5,5))
print("img1_resize=\n",img1_resize)
print("img2_resize=\n",img2_resize)
print("img1_resize+img2_resize=\n",img1_resize+img2_resize)

注：(139+149)%256=32

add()

$$a+b=\{\begin{array}{l}a+b,a+b\le 255\\ 255,a+b>255\end{array}$$

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(5,5))
img2_resize=cv2.resize(img2,(5,5))
print("img1_resize=\n",img1_resize)
print("img2_resize=\n",img2_resize)
img3 = cv2.add(img1_resize,img2_resize)
print("cv2.add(img1_resize,img2_resize)=\n",img3)

显示"+"、add()效果图

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(400,400))
img2_resize=cv2.resize(img2,(400,400))
cv2.imshow("origin",img1_resize)
cv2.imshow("img1_resize+img2_resize",img1_resize+img2_resize)
cv2.imshow("cv2.add(img1_resize,img2_resize)",cv2.add(img1_resize,img2_resize))
cv2.waitKey()
cv2.destroyAllWindows()

图像加权和addWeighted()

• res=cv2.addWeighted(img1, alpha, img2, beta, gamma)
• $$res=img1\times \alpha +img2\times \beta +\gamma$$
• 通俗地说，结果图像=图像1×系数1+图像2×系数2+亮度调节量

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(3,3))
img2_resize=cv2.resize(img2,(3,3))
res=cv2.addWeighted(img1_resize,0.6,img2_resize,5,3)
print("img1_resize=\n",img1_resize)
print("img2_resize=\n",img2_resize)
print("cv2.addWeighted(img1_resize,0.6,img1_resize,5,3)=\n",res)

注：1920.6+05+3=118

显示addWeighted()效果图

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(400,400))
img2_resize=cv2.resize(img2,(400,400))
res=cv2.addWeighted(img1_resize,0.6,img2_resize,5,3)
cv2.imshow("img1_resize",img1_resize)
cv2.imshow("img2_resize",img2_resize)
cv2.imshow("cv2.addWeighted(img1_resize,0.6,img2_resize,5,3)",res)
cv2.waitKey()
cv2.destroyAllWindows()

按位运算

函数名	基本含义
cv2.bitwise_and()	按位与
cv2.bitwise_or()	按位或
cv2.bitwise_xor()	按位异或
cv2.bitwise_not()	按位取反

import cv2
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(400,400))
img2_resize=cv2.resize(img2,(400,400))
cv2.imshow("cv2.bitwise_and(img1_resize,img2_resize)",cv2.bitwise_and(img1_resize,img2_resize))
cv2.imshow("cv2.bitwise_or(img1_resize,img2_resize)",cv2.bitwise_or(img1_resize,img2_resize))
cv2.imshow("cv2.bitwise_xor(img1_resize,img2_resize)",cv2.bitwise_xor(img1_resize,img2_resize))
cv2.imshow("cv2.bitwise_not(img1_resize,img2_resize)",cv2.bitwise_not(img1_resize,img2_resize))
cv2.waitKey()
cv2.destroyAllWindows()

掩模mask

res=cv2.add(img1 , img2 , mask)

import cv2
import numpy as np
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(5,5))
img2_resize=cv2.resize(img2,(5,5))
mask=np.zeros((5,5),dtype=np.uint8)
mask[2:4,2:4]=1
res=cv2.add(img1_resize,img2_resize, mask=mask)
print("img1_resize=\n",img1_resize)
print("img2_resize=\n",img2_resize)
print("mask=\n",mask)
print("cv2.add(img1_resize,img2_resize, mask=mask)=\n",res)

import cv2
import numpy as np
img1=cv2.imread("1.jpg",0)
img2=cv2.imread("2.jpg",0)
img1_resize=cv2.resize(img1,(400,400))
img2_resize=cv2.resize(img2,(400,400))
mask=np.ones((400,400),dtype=np.uint8)
mask[200:400,200:400]=0
res=cv2.add(img1_resize,img2_resize, mask=mask)
print("img1_resize=\n",img1_resize)
print("img2_resize=\n",img2_resize)
print("mask=\n",mask)
print("cv2.add(img1_resize,img2_resize, mask=mask)=\n",res)
cv2.imshow("cv2.add(img1_resize,img2_resize, mask=mask)",res)
cv2.waitKey()
cv2.destroyAllWindows()

参考文献

[1] https://opencv.org/

• 更多精彩内容，可点击进入
  OpenCV-Python快速入门专栏或我的个人主页查看