Clone an image in cv2 Python

Question

I'm new to OpenCV. What is the Python function which act the same as cv::clone() in C++?

I just try to get a rect by

    rectImg = img[10:20, 10:20]

but when I draw a line on it, I find the line appear both on img and the rectImage, so, how can I get this done?

score 127 · Accepted Answer · edited Jan 15 '23 at 17:54

127

Abid Rahman K's answer is correct, but you say that you are using cv2 which inherently uses NumPy arrays. So, to make a complete different copy of say "myImage":

newImage = myImage.copy()

The above is enough. There isn't any need to import NumPy (numpy).

edited Jan 15 '23 at 17:54

Peter Mortensen

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answered Feb 27 '16 at 07:22

Ash Ketchum

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score 69 · Answer 2 · edited Jan 15 '23 at 17:49

69

If you use cv2, the correct method is to use the .copy() method in NumPy. It will create a copy of the array you need. Otherwise it will produce only a view of that object.

For example:

In [1]: import numpy as np

In [2]: x = np.arange(10*10).reshape((10, 10))

In [4]: y = x[3:7, 3:7].copy()

In [6]: y[2, 2] = 1000

In [8]: 1000 in x
Out[8]: False     # See, 1000 in y doesn't change values in x, the parent array.

edited Jan 15 '23 at 17:49

Peter Mortensen

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answered May 14 '13 at 05:01

Abid Rahman K

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They are just numbers in range 0-100. Just print `x` and `y` after each step. Then you will get the idea. – Abid Rahman K Oct 07 '14 at 10:35

score 14 · Answer 3 · edited Jan 15 '23 at 17:55

14

Using Python 3 and opencv-python version 4.4.0, the following code should work:

img_src = cv2.imread('image.png')
img_clone = img_src.copy()

edited Jan 15 '23 at 17:55

Peter Mortensen

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answered Oct 13 '20 at 16:18

Ashadi Sedana Pratama

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is that actually an answer or a question? "I try using..." – Ruli Oct 13 '20 at 19:51
an answer actually @Ruli – Ashadi Sedana Pratama Oct 15 '20 at 17:13

score 1 · Answer 4 · edited Jan 15 '23 at 17:48

1

You can simply use the Python standard library. Make a shallow copy of the original image as follows:

import copy

original_img = cv2.imread("foo.jpg")
clone_img = copy.copy(original_img)

edited Jan 15 '23 at 17:48

Peter Mortensen

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answered Apr 21 '15 at 14:00

yildirim

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Shallow copies are harmful (RAM ownership is unclear, access-performance is unclear etc). – Mitch McMabers Oct 01 '19 at 16:30

score 1 · Answer 5 · answered May 14 '15 at 00:32

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My favorite method uses cv2.copyMakeBorder with no border, like so.

copy = cv2.copyMakeBorder(original,0,0,0,0,cv2.BORDER_REPLICATE)

answered May 14 '15 at 00:32

Jack Guy

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What's the benefit of the `copyMakeBorder` variant over the regular 'copy` ? Is it an attempt to avoid the notion of nparrays (which Python-OpenCV matrices are) appearing in source code? – Stéphane Gourichon Dec 19 '19 at 18:16

Clone an image in cv2 Python

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