Negative film and watermark effect (OpenCV)

Table of contents

1. The principle of negative film effect

2. The effect principle of watermark

3. Example picture

4. The complete code of negative film and watermark effect

5. Operation effect

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1. The principle of negative film effect

        Set the three-color value of the pixel to (255-original value. Set the image matrix as img, the code is as follows:

# 生成负片
    b, g, r = cv2.split(img)
    b = 255-b
    g = 255-g
    r = 255-r

2. The effect principle of watermark

        Call the putText function, take the image matrix as the first parameter, and the output content as the second parameter, and directly output the watermark text on the image. code show as below:

 加上水印
    cv2.putText(img,'HELLO WORLD', (20,20), cv2.FONT_HERSHEY_PLAIN, 2.0, (0, 0, 0), thickness = 2)
    # 文本的位置在坐标(20,20)，使用字体cv2.FONT_HERSHEY_PLAIN，字体大小为2.0，颜色为黑色(0,0,0)，线条粗细为2。
    cv2.putText(img,'HELLO MACHINE LEARNING', (20,100), cv2.FONT_HERSHEY_PLAIN, 1.0, (0, 0, 0), thickness = 2)

3. Example picture

4. The complete code of negative film and watermark effect

import cv2
import numpy as np

fn = r"C:\Users\LIHAO\Pictures\Saved Pictures\wallhaven-1pdk1v.jpg"
if __name__ == '__main__':
    img = cv2.imread(fn)
    w=img.shape[1]
    h=img.shape[0]
    # 生成负片
    b, g, r = cv2.split(img)
    b = 255-b
    g = 255-g
    r = 255-r
    # 直接通过索引改变色彩分量
    img[:,:,0]=b
    img[:,:,1]=g
    img[:,:,2]=r
    # 加上水印
    cv2.putText(img,'HELLO WORLD', (100,1000), cv2.FONT_HERSHEY_PLAIN, 2.0, (0, 0, 0), thickness = 2)
    # 文本的位置在坐标(100,1000)，使用字体cv2.FONT_HERSHEY_PLAIN，字体大小为2.0，颜色为黑色(0,0,0)，线条粗细为2。
    cv2.putText(img,'HELLO MACHINE LEARNING', (600,100), cv2.FONT_HERSHEY_PLAIN, 1.0, (0, 0, 0), thickness = 2)
    
    cv2.namedWindow('img')
    cv2.imshow('img', img)
    cv2.waitKey()
    cv2.destroyAllWindows()

5. Operation effect