使用python写一个程序，将指定路径下的所有视频resize到1920×1080，并将其贴到2560×1440的黑色背景上，并另存为avi格式

好的，你可以使用OpenCV库实现这个功能。以下是一个示例代码：

import os
import cv2

# 指定路径下的所有视频文件夹
path = "/path/to/videos"
videos_folder = ["folder1", "folder2", "folder3"]

# 遍历所有视频文件夹
for folder in videos_folder:
    # 获取视频文件夹路径
    folder_path = os.path.join(path, folder)
    
    # 获取视频文件夹下的所有视频文件
    videos = [f for f in os.listdir(folder_path) if f.endswith('.mp4')]

    # 遍历所有视频文件
    for video in videos:
        # 读取视频
        cap = cv2.VideoCapture(os.path.join(folder_path, video))

        # 获取视频帧率和尺寸
        fps = cap.get(cv2.CAP_PROP_FPS)
        width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
        height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

        # 创建一个空白画布
        canvas = 255 * np.ones((1440, 2560, 3), dtype=np.uint8)

        # 遍历视频的每一帧
        while cap.isOpened():
            ret, frame = cap.read()
            if ret:
                # 将帧resize到1920x1080
                frame = cv2.resize(frame, (1920, 1080))

                # 将帧贴到画布上
                x_offset = int((2560 - 1920) / 2)
                y_offset = int((1440 - 1080) / 2)
                canvas[y_offset:y_offset+1080, x_offset:x_offset+1920] = frame

                # 显示画布
                cv2.imshow('canvas', canvas)

                # 暂停一段时间，以达到视频帧率
                cv2.waitKey(int(1000/fps))
            else:
                break

        # 释放视频资源
        cap.release()
        cv2.destroyAllWindows()

        # 保存视频
        fourcc = cv2.VideoWriter_fourcc(*'XVID')
        out = cv2.VideoWriter(os.path.join(folder_path, video[:-4] + '_resized.avi'), fourcc, fps, (2560, 1440))
        cap = cv2.VideoCapture(os.path.join(folder_path, video))
        while cap.isOpened():
            ret, frame = cap.read()
            if ret:
                frame = cv2.resize(frame, (1920, 1080))
                x_offset = int((2560 - 1920) / 2)
                y_offset = int((1440 - 1080) / 2)
                canvas[y_offset:y_offset+1080, x_offset:x_offset+1920] = frame
                out.write(canvas)
            else:
                break

        # 释放视频资源
        cap.release()
        out.release()
        cv2.destroyAllWindows()

你需要将`/path/to/videos`替换为你的视频文件夹路径，将`folder1`、`folder2`、`folder3`替换为你要处理的视频文件夹名。这段代码会遍历每个视频文件夹，读取视频文件夹下的所有视频文件，并遍历每个视频文件，将其resize到1920x1080并贴到2560x1440的黑色背景上，然后另存为avi格式。保存的文件名格式为`video_resized.avi`。