image processing - 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.

The black edges are useless so that I want to cut them, only leaving the Windows icon (and the blue background).

I do not want to calculate the coordinate and the size of the Windows icon. GIMP and Photoshop have sort of autocrop function. OpenCV does not have one?

Answer 1

I am not sure whether all your images are like this. But for this image, below is a simple python-opencv code to crop it.

first import libraries :

import cv2
import numpy as np

Read the image, convert it into grayscale, and make in binary image for threshold value of 1.

img = cv2.imread('sofwin.png')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
_,thresh = cv2.threshold(gray,1,255,cv2.THRESH_BINARY)

Now find contours in it. There will be only one object, so find bounding rectangle for it.

contours,hierarchy = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)
cnt = contours[0]
x,y,w,h = cv2.boundingRect(cnt)

Now crop the image, and save it into another file.

crop = img[y:y+h,x:x+w]
cv2.imwrite('sofwinres.png',crop)

Below is the result :