OpenCV 添加透明水印 -＞ png透明图像叠加在jpg图像上

import cv2
import numpy as np
 
def add_alpha_channel(img):
    """ 为jpg图像添加alpha通道 """
 
    b_channel, g_channel, r_channel = cv2.split(img) # 剥离jpg图像通道
    alpha_channel = np.ones(b_channel.shape, dtype=b_channel.dtype) * 255 # 创建Alpha通道
 
    img_new = cv2.merge((b_channel, g_channel, r_channel, alpha_channel)) # 融合通道
    return img_new
 
def merge_img(jpg_img, png_img, y1, y2, x1, x2):
    """ 将png透明图像与jpg图像叠加 
        y1,y2,x1,x2为叠加位置坐标值
    """
    
    # 判断jpg图像是否已经为4通道
    if jpg_img.shape[2] == 3:
        jpg_img = add_alpha_channel(jpg_img)
    
    '''
    当叠加图像时，可能因为叠加位置设置不当，导致png图像的边界超过背景jpg图像，而程序报错
    这里设定一系列叠加位置的限制，可以满足png图像超出jpg图像范围时，依然可以正常叠加
    '''
    yy1 = 0
    yy2 = png_img.shape[0]
    xx1 = 0
    xx2 = png_img.shape[1]
 
    if x1 < 0:
        xx1 = -x1
        x1 = 0
    if y1 < 0:
        yy1 = - y1
        y1 = 0
    if x2 > jpg_img.shape[1]:
        xx2 = png_img.shape[1] - (x2 - jpg_img.shape[1])
        x2 = jpg_img.shape[1]
    if y2 > jpg_img.shape[0]:
        yy2 = png_img.shape[0] - (y2 - jpg_img.shape[0])
        y2 = jpg_img.shape[0]
 
    # 获取要覆盖图像的alpha值，将像素值除以255，使值保持在0-1之间
    alpha_png = png_img[yy1:yy2,xx1:xx2,3] / 255.0
    alpha_jpg = 1 - alpha_png
    
    # 开始叠加
    for c in range(0,3):
        jpg_img[y1:y2, x1:x2, c] = ((alpha_jpg*jpg_img[y1:y2,x1:x2,c]) + (alpha_png*png_img[yy1:yy2,xx1:xx2,c]))
 
    return jpg_img
 
if __name__ == '__main__':
    # 定义图像路径
    img_jpg_path = 'imgs/0.jpg' # 读者可自行修改文件路径
    img_png_path = 'imgs/0.png' # 读者可自行修改文件路径
 
    # 读取图像
    img_jpg = cv2.imread(img_jpg_path, cv2.IMREAD_UNCHANGED)
    img_png = cv2.imread(img_png_path, cv2.IMREAD_UNCHANGED)
 	# 居中处理
 	height, width,tongdao = img_jpg.shape
 	h_logo, w_logo,_ image_png.shape
 	center_y = int(height/2)
 	center_x = int(width/2)
 	
    # 设置叠加位置坐标
    # 从(左上,右下)计算
    x1 = center_x  - int(w_logo/2)
    y1 = center_y- int(h_logo/2)
    x2 = x1 + w_logo
    y2 = y1 + h_logo
 
    # 开始叠加
    res_img = merge_img(img_jpg, img_png, y1, y2, x1, x2)
 
    # 显示结果图像
    cv2.imshow('result', res_img)
 
    # 保存结果图像，读者可自行修改文件路径
    cv2.imwrite('imgs/res.jpg', res_img)
 
    # 定义程序退出方式：鼠标点击显示图像的窗口后，按ESC键即可退出程序
    if cv2.waitKey(0) & 0xFF == 27:
        cv2.destroyAllWindows()

如何将透明底改为白色
https://www.cnblogs.com/jaysonteng/p/12793178.html
添加透明图片
https://www.cnblogs.com/zhaoyingjie/p/14699837.html
https://blog.csdn.net/weixin_40065609/article/details/114886234