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November 28, 2018 06:39
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Quickly extract N keyframes from a video (requires python2 and opencv)
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from __future__ import division | |
import sys | |
import cv2 | |
import contextlib | |
def main(num_keyframes, filepath): | |
print("Extracting {} keyframes from '{}'...".format(num_keyframes, filepath)) | |
with video_file(filepath) as video: | |
for title, keyframe in get_keyframes(video, num_keyframes): | |
cv2.imwrite(title, keyframe) | |
print("Done.") | |
@contextlib.contextmanager | |
def video_file(path): | |
v = cv2.VideoCapture(path) | |
yield v | |
v.release() | |
def get_keyframes(video, num_keyframes): | |
num_frames = int(video.get(cv2.cv.CV_CAP_PROP_FRAME_COUNT)) | |
for i in range(num_keyframes): | |
title = "{}.png".format(i) | |
keyframe = get_keyframe(video, num_frames, num_keyframes, i) | |
yield title, keyframe | |
def get_keyframe(video, num_frames, num_keyframes, index): | |
percentage = (index + 1)/(num_keyframes + 2) | |
frame_index = int(percentage * num_frames) | |
print("Extracting keyframe {}/{} (frame {})...".format(index + 1, num_keyframes, frame_index)) | |
video.set(cv2.cv.CV_CAP_PROP_POS_FRAMES, frame_index) | |
return video.read()[1] | |
if __name__ == "__main__": | |
if len(sys.argv) == 3: | |
main(int(sys.argv[2]), sys.argv[1]) | |
else: | |
print("Please specify the arguments: <video_file> <number_of_keyframes>") | |
sys.exit(1) |
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