I want to apply zoom in and out effect on a video using opencv, but as opencv doesn’t come with built in zoom, I try cropping the frame to the interpolated value’s width, height, x and y and than resize back the frame to the original video size, i.e. 1920 x 1080.

But when I rendered the final video, there is shakiness in the final video. I am not sure why its happening, I want a perfect smooth zoom in and out from the specific time

I built a easing function that would give interpolated value for each frame for zoom in and out :-

import cv2


video_path = 'inputTest.mp4'
cap = cv2.VideoCapture(video_path)

fps = int(cap.get(cv2.CAP_PROP_FPS)) 
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
out = cv2.VideoWriter('output_video.mp4', fourcc, fps, (1920, 1080))

initialZoomValue={
     'initialZoomWidth': 1920,
    'initialZoomHeight': 1080,
    'initialZoomX': 0,
    'initialZoomY': 0
}

desiredValues = {
     'zoomWidth': 1672,
     'zoomHeight': 941,
     'zoomX': 200,
     'zoomY': 0
}

def ease_out_quart(t):
    return 1 - (1 - t) ** 4

async def zoomInInterpolation(initialZoomValue, desiredZoom, start, end, index):
    t = (index - start) / (end - start)
    eased_t = ease_out_quart(t)

    interpolatedWidth = round(initialZoomValue['initialZoomWidth'] + eased_t * (desiredZoom['zoomWidth']['width'] - initialZoomValue['initialZoomWidth']), 2)
    interpolatedHeight = round(initialZoomValue['initialZoomHeight'] + eased_t * (desiredZoom['zoomHeight'] - initialZoomValue['initialZoomHeight']), 2)
    interpolatedX = round(initialZoomValue['initialZoomX'] + eased_t * (desiredZoom['zoomX'] - initialZoomValue['initialZoomX']), 2)
    interpolatedY = round(initialZoomValue['initialZoomY'] + eased_t * (desiredZoom['zoomY'] - initialZoomValue['initialZoomY']), 2)
    
    return {'interpolatedWidth': int(interpolatedWidth), 'interpolatedHeight': int(interpolatedHeight), 'interpolatedX': int(interpolatedX), 'interpolatedY': int(interpolatedY)}

def generate_frame():
        while cap.isOpened():
            code, frame = cap.read()
            if code:
                yield frame
            else:
                print("bailsdfing")
                break


for i, frame in enumerate(generate_frame()):
   if i >= 1 and i <= 60:
        interpolatedValues = zoomInInterpolation(initialZoomValue, desiredValues, 1, 60, i)
        crop = frame[interpolatedValues['interpolatedY']:(interpolatedValues['interpolatedHeight'] + interpolatedValues['interpolatedY']), interpolatedValues['interpolatedX']:(interpolatedValues['interpolatedWidth'] + interpolatedValues['interpolatedX'])]
        zoomedFrame = cv2.resize(crop,(1920, 1080), interpolation = cv2.INTER_CUBIC) 

        out.write(zoomedFrame)

# Release the video capture and close windows
cap.release()
cv2.destroyAllWindows()

But the final video I get is shaking :-

Final Video

I want the video to be perfectly zoom in and out, don’t want to any shakiness