A simple way is to use ImageMagick and composite the frames with a lightening blend so the brightest parts of each frame remain, which works well for light painting.

Example: convert -compose lighten 1.jpg 2.jpg -composite 3.jpg -composite 4.jpg -composite result.jpg

This stacks the images and keeps the lighter pixels from each frame, building up the light trails into one final image. For many frames, you’d extend the command with the rest of the files in sequence.

If your exported frames are aligned and shot from a fixed camera, this is an effective approach for creating a single “light graffiti” image from video.