Teaching the kids how to code and make stop motion animations!

stopmotion.py

import numpy as np
import cv2
import argparse
import os
import subprocess

parser = argparse.ArgumentParser()
parser.add_argument('dev', help='video device')
parser.add_argument('out', help='output folder')
args = parser.parse_args()

cap = cv2.VideoCapture(args.dev)
frame_count=0
last_saved_frame = None
os.makedirs(args.out)

cv2.namedWindow('frame', 0)

while True:
    # Capture frame-by-frame
    ret, frame = cap.read()
    if frame is None:
        continue

    if last_saved_frame is None:
        last_saved_frame = frame
        
    display = frame * 0.75 + last_saved_frame*0.25           

    # Display the resulting frame
    cv2.imshow('frame', display/255)

    key = cv2.waitKey(10) & 0xFF
   
    if key == ord(' '):
        frame_count+=1
        last_saved_frame = frame[:]
        out_file=os.path.join(args.out,'%05d.png'%frame_count)
        print('saving %s'%out_file)
        cv2.imwrite(out_file, frame)
    elif key == ord('s'):
        cmd="convert  -delay 15 %s/*.png +dither  +map %s.gif"%(args.out, args.out)
        print(cmd)
        subprocess.check_call(cmd, shell=True)
    elif key != 255:
        print('you pressed %s'%chr(key))
    if key == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

Our first animations, made with convert:

convert -delay 5 *.png joules_first.gif 

Now it writes out the gif while you're working. Convenient to open up the gif and watch it while you're animating.

Magnets on a white board by Dad:

Portal by Joule: