How to tell what the size of an image is after removing seams in using OpenCV2 in Python?

Question

I am trying to write some code to manipulate the individual images, "frames", from a live video from the webcam in Python using OpenCV2. I am able to manipulate the frames but I have this excess bit of the image along the edges.

Frame:

I would like the "black areas" to not be in frame so I am wondering how to manipulate the size of the canvas to allow the black areas to not be visible.

What I would like the frame to look like:

Does anyone know what code I could use to crop the canvas size?

Answer 1

You could use a Python subprocessing call to ImageMagick command line -trim function to remove any black that touches the sides of the image.

See https://imagemagick.org/discourse-server/viewtopic.php?f=4&t=35579

Input:

import subprocess
cmd = 'convert seams1.png -fuzz 0% -background black -define trim:percent-background=0% -trim +repage result.png'
subprocess.check_output(cmd, shell=True, universal_newlines=True)

or

import subprocess
cmd = 'convert seams1.png -fuzz 0% -background black -define trim:percent-background=0% -trim +repage result.png'
subprocess.call(cmd, shell=True)