Crop an image in multiple rectangles and combine them into one in Python OpenCV

Question

I've been referred to How to crop an image in OpenCV using Python, but my question has a little difference.

This can be a numpy-slicing problem. I know I can do:

import cv2
img = cv2.imread("test_image.jpg")
crop_img = img[y:y+h, x:x+w]

But what if I need two rectangles with the same y range but non-consecutive x ranges of the original picture? I've tried:

crop_img = img[y:y+h, [x1:x1+w1, x2:x2+w2]]

What I expected was a rectangular having its height from y to y+h, and its width from x1 to x1+w1 plus x2 to x2+w2, where x1+w1 doesn't have to be equal to x2. Nevertheless I get a SyntaxError with "invalid syntax". Is there a way to correctly achieve my goal?

eyllanesc · Accepted Answer · 2018-05-03 04:42:58Z

2

You have to extract each part and then concatenate with the help of the concatenate function of numpy.

import numpy as np

v1 = img[y:y+h, x1:x1+w1]
v2 = img[y:y+h, x2:x2+w2]

v = np.concatenate((v1, v2), axis=1)

Or:

indexes = ((x1, w1), (x2, w2))
v = np.concatenate([img[y: y+h , v1: v1+v2] for v1,v2 in indexes], axis=1)

Another way:

Creating indexes as lists

v = img[y:y+h, list(range(x1, x1+w1)) + list(range(x2, x2 + w2))]

edited May 3, 2018 at 4:42

answered May 3, 2018 at 4:21

eyllanesc

246k19 gold badges205 silver badges282 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Daniel F Over a year ago

Reminder w1 must be equal to w2 for this to work without getting dtype=object arrays (which will likely break any follow-on code). If they aren't you probably just want to output a list of nD subarrays instead of a (n+1)D array.

Collectives™ on Stack Overflow

Crop an image in multiple rectangles and combine them into one in Python OpenCV

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related