How to copy a image region using opencv in python?

python image opencv image-processing roi
curumim picture curumim · Jan 31, 2012 · Viewed 99.5k times · Source

I am trying to implement a license plate recognition software using the ideas from http://iamabhik.wordpress.com/category/opencv/.

I implemented the plate location using opencv in python, using "import cv2". It works okay and now I need to copy the plate region to another image to do the segmentation of the characters and then the OCR part (maybe using a neural network).

I found the GetSubRect() function to copy or isolate part of the image but it does not appear to be available in python. Is there an alternative? The ROI functions do not seem to be implemented either.

Is there an up-to-date documentation of the python interface to opencv?

I compiled opencv from svn repository (revision 7239) on a Debian wheezy/sid environment.

Fell free to suggest alternative methods/ideas to solve this problem.

Thanks in advance.

Answer

Abid Rahman K picture Abid Rahman K · Jan 31, 2012

Both cv.GetSubRect and ROI functions are available in Python, but in old import cv mode or import cv2.cv. ie use cv2.cv.GetSubRect() or cv2.cv.SetImageROI if you are familier with them.

On the other hand, it is simple to set ROI without these functions due to numpy integration in new cv2.

If (x1,y1) and (x2,y2) are the two opposite vertices of plate you obtained, then simply use function:

roi = gray[y1:y2, x1:x2]

that is your image ROI.

So choose whatever suit you.

Related questions

Region of Interest opencv python

I am trying to get a region of an image (ROI) using opencv python. The version of opencv used is 2.4.3. However when I try to call the API cv2.SetImageROI it returns this error AttributeError: 'module' object has no attribute …

Read More
How to resize an image with OpenCV2.0 and Python2.6

I want to use OpenCV2.0 and Python2.6 to show resized images. I used and adopted this example but unfortunately, this code is for OpenCV2.1 and does not seem to be working on 2.0. Here my code: import os, glob import cv …

Read More
OpenCV & Python - Image too big to display

I have an image that is 6400 × 3200, while my screen is 1280 x 800. Therefore, the image needs to be resized for display only. I am using Python and OpenCV 2.4.9. According to OpenCV Documentation, If you need to show an image that is …

Read More