将透明视频叠加到相机馈送 OpenCV

Question

I've been searching how to overlay transparent video to camera feed in Python (or actually in any language) and the closest thing I've seen is using opencv .

I followed the tutorials here and did some experiments. One is adding a new VideoCapture inside the while loop to play video from files when capturing video from camera; but the video won't show up.

Other things I came across are mixing videos and camera feed but not really doing an overlay.

I'm lost in track and any tutorials or links on how to do it programmatically are highly appreciated.

UPDATE: This is about loading the camera feed and transparent video frame-by-frame and time-by-time simultaneously.

Answer 1

import cv2
import time
import numpy as np

current_milli_time = lambda: int(round(time.time() * 1000))

# Camera feed
cap_cam = cv2.VideoCapture(0)
if not cap_cam.isOpened():
    print('Cannot open camera')
    exit()
ret, frame_cam = cap_cam.read()
if not ret:
    print('Cannot open camera stream')
    cap_cam.release()
    exit()

# Video feed
filename = 'myvideo.mp4'
cap_vid = cv2.VideoCapture(filename)
if not cap_cam.isOpened():
    print('Cannot open video: ' + filename)
    cap_cam.release()
    exit()
ret, frame_vid = cap_vid.read()
if not ret:
    print('Cannot open video stream: ' + filename)
    cap_cam.release()
    cap_vid.release()
    exit()

# Specify maximum video time in milliseconds
max_time = 1000 * cap_vid.get(cv2.CAP_PROP_FRAME_COUNT) / cap_vid.get(cv2.CAP_PROP_FPS)

# Resize the camera frame to the size of the video
height = int(cap_vid.get(cv2.CAP_PROP_FRAME_HEIGHT))
width = int(cap_vid.get(cv2.CAP_PROP_FRAME_WIDTH))

# Starting from now, syncronize the videos
start = current_milli_time()

while True:
    # Capture the next frame from camera
    ret, frame_cam = cap_cam.read()
    if not ret:
        print('Cannot receive frame from camera')
        break
    frame_cam = cv2.resize(frame_cam, (width, height), interpolation = cv2.INTER_AREA)

    # Capture the frame at the current time point
    time_passed = current_milli_time() - start
    if time_passed > max_time:
        print('Video time exceeded. Quitting...')
        break
    ret = cap_vid.set(cv2.CAP_PROP_POS_MSEC, time_passed)
    if not ret:
        print('An error occured while setting video time')
        break
    ret, frame_vid = cap_vid.read()
    if not ret:
        print('Cannot read from video stream')
        break

    # Blend the two images and show the result
    tr = 0.3 # transparency between 0-1, show camera if 0
    frame = ((1-tr) * frame_cam.astype(np.float) + tr * frame_vid.astype(np.float)).astype(np.uint8)
    cv2.imshow('Transparent result', frame)
    if cv2.waitKey(1) == 27: # ESC is pressed
        break

cap_cam.release()
cap_vid.release()
cv2.destroyAllWindows()