Crop black edges with OpenCV

Question

I think it should be a very simple problem, but I cannot find a solution or an effective keyword for search.

I just have this image.

Answer 1

How about a slick little recursive function?

import cv2
import numpy as np
def trim(frame):
    #crop top
    if not np.sum(frame[0]):
        return trim(frame[1:])
    #crop bottom
    elif not np.sum(frame[-1]):
        return trim(frame[:-2])
    #crop left
    elif not np.sum(frame[:,0]):
        return trim(frame[:,1:]) 
    #crop right
    elif not np.sum(frame[:,-1]):
        return trim(frame[:,:-2])    
    return frame

Load and threshold the image to ensure the dark areas are black:

img = cv2.imread("path_to_image.png")   
thold = (img>120)*img

Then call the recursive function

trimmedImage = trim(thold)