OpenCV:如何将所有非透明像素的颜色改为黑色？

import cv2
import numpy as np

# 加载图像
image = cv2.imread("image.png", cv2.IMREAD_UNCHANGED)

# 提取非透明区域
height, width, channels = image.shape
non_transparent_pixels = []
for y in range(height):
    for x in range(width):
        if image[y, x][3] != 0:  # 检查透明度值
            non_transparent_pixels.append((y, x))

# 修改颜色
for pixel in non_transparent_pixels:
    image[pixel[0], pixel[1]] = (0, 0, 0, 255)  # 设置为黑色

# 保存图像
cv2.imwrite("modified_image.png", image)