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February 3, 2017 19:27
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Turn yourself into a slinky by time-delaying successive chunks of a webcam capture with OpenCV! https://vimeo.com/183155228
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import copy | |
import datetime | |
import numpy as np | |
from optparse import OptionParser | |
import time | |
import cv2 | |
from matplotlib import pyplot as plt | |
SHIFT_HEIGHT = 5 | |
EPOCH = datetime.datetime.utcfromtimestamp(0) | |
def unix_time(dt): | |
return (dt - EPOCH).total_seconds() * 1.0 | |
def get_unix_now(): | |
return unix_time(datetime.datetime.now()) | |
def get_frame(cam): | |
ret, frame = cam.read() | |
if not ret: | |
return | |
frame = cv2.resize(frame, (0,0), fx=0.3, fy=0.3) | |
return frame | |
def np_rotate_array(arr, shift): | |
"""Shift a numpy array to the right so that it wraps around.""" | |
return np.concatenate([arr[shift:], arr[:shift]]) | |
def fingerprint_frame(frame): | |
""" For quick dirty debugging """ | |
return sum(sum(sum(frame))) | |
def main(): | |
parser = OptionParser() | |
parser.add_option('-f', dest='input_name', default=0, | |
help='input video file (leave blank to use webcam)') | |
parser.add_option('-o', dest='output_name', | |
help='output video file') | |
parser.add_option('--time', action='store_true', default=False, | |
help='time it') | |
(options, args) = parser.parse_args() | |
cam = cv2.VideoCapture(options.input_name) | |
frame = get_frame(cam) | |
height = len(frame) | |
width = len(frame[0]) | |
print 'frame size: %d x %d px' % (width, height) | |
# Retain a rolling buffer of time-delayed versions of the image, | |
# back to `height` frames ago | |
# TODO later: performance optimize by only keeping the triangle of delay rows | |
# we need (since the top row is delayed by 0 frames, we don't need any) | |
delay_buffer = [] | |
# TODO later: worry about it not dividing perfectly into height | |
TIME_TRAVEL_LIMIT = height / SHIFT_HEIGHT | |
# Define the codec and create VideoWriter object | |
out = None | |
if options.output_name: | |
fourcc = cv2.cv.CV_FOURCC(*'mp4v') | |
out = cv2.VideoWriter(options.output_name, fourcc, 20.0, (width, height)) | |
if options.time: | |
frame_execution_times = [] | |
frame_mod = 0 | |
# Begin main video processing loop | |
while cam.isOpened(): | |
start = get_unix_now() | |
# Capture frame-by-frame | |
frame = get_frame(cam) | |
if frame is None: | |
break | |
image = copy.deepcopy(frame) | |
# Roll delay buffer forward | |
delay_buffer.insert(0, copy.deepcopy(frame)) | |
delay_buffer = delay_buffer[:min(TIME_TRAVEL_LIMIT, len(delay_buffer))] | |
# Weird swirly time-delayed image | |
# `i`th frame ago for SHIFT_HEIGHT * i : SHIFT_HEIGHT * (i+1) rows | |
image = frame | |
for delay in xrange(TIME_TRAVEL_LIMIT): | |
if delay < len(delay_buffer): | |
for j in xrange(SHIFT_HEIGHT): | |
row_index = delay * SHIFT_HEIGHT + j | |
image[row_index] = delay_buffer[delay][row_index] | |
# Wacky funhouse mirror (make image slanted) | |
#for i, row in enumerate(image): | |
# image[i] = np_rotate_array(row, i) | |
# Edge detection for fun | |
#image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY) | |
#image = cv2.Canny(image, 60, 120) | |
# Display the resulting frame | |
if frame_mod % 5 == 0: | |
cv2.imshow('frame', image) | |
frame_mod += 1 | |
# Save to output | |
if out and image is not None: | |
#image = cv2.cvtColor(image, cv2.COLOR_GRAY2RGB) | |
out.write(image) | |
if options.time: | |
frame_execution_times.append(get_unix_now() - start) | |
# Check for quit signal | |
if cv2.waitKey(1) & 0xFF == ord('q'): | |
break | |
previous_frame = frame | |
# When everything done, release the camture | |
cam.release() | |
if out: | |
out.release() | |
cv2.destroyAllWindows() | |
if options.time: | |
print 'Frame execution times (%d frames taken):' % len(frame_execution_times) | |
print 'avg:', sum(frame_execution_times)/len(frame_execution_times) | |
print 'stddev:', np.std(frame_execution_times) | |
if __name__ == '__main__': | |
main() |
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