opencv视频上的透明画布

import cv2
import numpy as np

# 读取视频文件
video = cv2.VideoCapture('input_video.mp4')

# 加载透明画布（假设是一个 PNG 文件）
overlay = cv2.imread('transparent_overlay.png', cv2.IMREAD_UNCHANGED)

while True:
    ret, frame = video.read()
    if not ret:
        break

    # 获取透明画布的尺寸
    overlay_height, overlay_width = overlay.shape[:2]

    # 计算画布在视频帧上的位置
    x = (frame.shape[1] - overlay_width) // 2
    y = (frame.shape[0] - overlay_height) // 2

    # 分离透明画布的 alpha 通道
    alpha_s = overlay[:, :, 3] / 255.0
    alpha_l = 1.0 - alpha_s

    # 叠加透明画布到视频帧上
    for c in range(0, 3):
        frame[y:y+overlay_height, x:x+overlay_width, c] = (
            alpha_s * overlay[:, :, c] +
            alpha_l * frame[y:y+overlay_height, x:x+overlay_width, c]
        )

    # 显示结果帧
    cv2.imshow('Video with Overlay', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

video.release()
cv2.destroyAllWindows()