python将png图片灰度化并保持透明的地方

import cv2
import numpy as np

def convert_to_grayscale_with_alpha(input_image_path, output_image_path):
    # 读取彩色图像，包括alpha通道
    image = cv2.imread(input_image_path, cv2.IMREAD_UNCHANGED)
    
    if image is None:
        print(f"Error: Could not read the image at {input_image_path}")
        return
    
    # 分离颜色通道和alpha通道
    b, g, r, a = cv2.split(image)
    
    # 将BGR图像转换为灰度图像
    grayscale_image = cv2.cvtColor(image, cv2.COLOR_BGRA2GRAY)
    
    # 创建一个与原图大小相同、且所有通道都填充灰度值的图像
    grayscale_with_alpha = cv2.merge((grayscale_image, grayscale_image, grayscale_image, a))
    
    # 保存结果
    cv2.imwrite(output_image_path, grayscale_with_alpha)
    print(f"Grayscale image with alpha saved to {output_image_path}")

# 使用示例
input_image_path = r"C:\Users\admins\Desktop\pz.png"  # 替换为你的输入图片路径
output_image_path = r'C:\Users\admins\Desktop\grayscale_output_image.png'  # 输出灰度图的保存路径
convert_to_grayscale_with_alpha(input_image_path, output_image_path)