jlengrand.github.io/_posts/2011-10-27-opencv-rect-expects-four-integers.markdown

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layout	status	published	title	author	author_login	author_email	author_url	wordpress_id	wordpress_url	date	categories	tags	comments
post	publish	true	OpenCV : 'rect' expects four integers	Julien Lengrand-Lambert	jlengrand	julien@lengrand.fr	http://www.lengrand.fr	207	http://www.lengrandlambert.fr/wordpress/?p=207	2011-10-27 09:48:25.000000000 +02:00	programming OpenCV Computer Vision Python	windows image processing

You may encounter this error when using OpenCV with Python bindings, while trying to use the rectangle structure.

Here is an example :

{% highlight python %} #!/usr/bin/env python

import cv

img = cv.LoadImage("test.jpg") dims = cv.GetSize(img) roi = [0, 0, dims[0] / 2, dims[1] / 2 ] cv.SetImageROI(img, roi) {% endhighlight %}

You will get this result:

{% highlight python %} Traceback (most recent call last): File "newfile.py", line 8, in cv.SetImageROI(img, roi) TypeError: CvRect argument 'rect' expects four integers {% endhighlight %}

The answer is pretty simple, you have to set rect as a tuple and not a list:

{% highlight python %} roi = (0, 0, dims[0] / 2, dims[1] / 2 ) {% endhighlight %}

There it is, pretty simple, isn't?!

I still lost 15 minuts searching for it yesterday ^^, won't do it twice :D

A small warning however, the values of the tuple can't be changed once initialized !

See ya