111 lines
2.7 KiB
Python
111 lines
2.7 KiB
Python
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import argparse
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import cv2 as cv
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from itertools import count
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import numpy as np
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def duration(cap):
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"""
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return the duration of the capture in seconds
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"""
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nframes = int(cap.get(cv.CAP_PROP_FRAME_COUNT))
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fps = cap.get(cv.CAP_PROP_FPS)
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return nframes / fps
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def capture_shape(cap):
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"""
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return the shape of the video capture
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"""
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nframes = int(cap.get(cv.CAP_PROP_FRAME_COUNT))
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height = int(cap.get(cv.CAP_PROP_FRAME_HEIGHT))
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width = int(cap.get(cv.CAP_PROP_FRAME_WIDTH))
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return (nframes, height, width)
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def transposed_shape(shape, axis):
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"""
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return the shape of the video capture after transposing the given axis to
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become the new time axis
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"""
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nframes, height, width = shape
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if axis == 1:
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new_shape = (height, nframes, width)
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elif axis == 2:
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new_shape = (width, height, nframes)
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return new_shape
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def transpose_frame(infile, n, axis):
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"""
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compute the nth frame of the input file after transposing the given axis to
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become the new time axis
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"""
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cap = cv.VideoCapture(infile)
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shape = capture_shape(cap)
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_, height, width = transposed_shape(shape, axis)
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tframe = np.empty((height, width, 3), np.dtype('uint8'))
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for i in count(0):
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# NOTE: reading each frame of the input to produce one output frame is
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# CPU-intensive, but to read the frames fewer times, we would have to
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# store the frames in memory, which is memory-intensive
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ret, frame = cap.read()
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if not ret:
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break
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if axis == 1:
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tframe[i] = frame[n]
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elif axis == 2:
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tframe[:, i] = frame[:, n]
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cap.release()
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return tframe
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def transpose_capture(infile, outfile, axis):
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"""
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transpose the input file along the given axis, storing the output in
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outfile
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"""
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cap = cv.VideoCapture(infile)
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seconds = duration(cap)
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shape = capture_shape(cap)
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nframes, height, width = transposed_shape(shape, axis)
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fps = nframes / seconds
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cap.release()
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fourcc = cv.VideoWriter.fourcc(*'h264')
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out = cv.VideoWriter(outfile, fourcc, fps, (width, height))
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for i in range(0, nframes):
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tframe = transpose_frame(infile, i, axis)
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out.write(tframe)
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out.release()
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cv.destroyAllWindows()
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if __name__ == "__main__":
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parser = argparse.ArgumentParser()
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parser.add_argument("source")
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parser.add_argument("dest")
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group = parser.add_mutually_exclusive_group(required=True)
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group.add_argument("--height", action='store_true')
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group.add_argument("--width", action='store_true')
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args = parser.parse_args()
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if args.height:
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axis = 1
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elif args.width:
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axis = 2
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transpose_capture(args.source, args.dest, axis)
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