Crop an ellipse form from an image instead of drawing it inside in OpenCV

Question

I have a rectangle that I want to extract the ellipse form of it from a given image. My code looks like:

RotatedRect ellipse ;
float p1 = (float) rect.width/2 + rect.x;
float p2 = (float) rect.height/2 + rect.y;
CvPoint2D32f p = cvPoint2D32f(p1,p2);
ellipse.center = p;
ellipse.angle = 0;
ellipse.size =  cvSize2D32f((float)rect.width, (float)rect.height);
ellipse( image_colored, minEllipse, CV_RGB(255,255,255), 2, 8 );

The input of this code are: an image (image_colored) and CvRect (rect). The last line of code, draws a white ellipse inside the "image_colored", but I am looking to crop the generated ellipse in an other image or just color the rest of the image in black.

Any help, will be highly appreciated. Thank you.

PS: I can not use the function cvEllipse(...) as it was suggested in this link. Because cvEllipse does not accept an object of type CvPoint2D32f, neither CvSize2D32f type.

"I can not use the function cvEllipse(...) as it was suggested" -- that's ok. stick with the c++ api for the better. avoid any cv*functions or structures from the deprecated c-api — berak, Dec 16 '13 at 18:33

score 2 · Answer 1 · edited May 23 '17 at 12:19

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Make an image with a filled ellipse and use this as a mask combined (bitwise and) with your image OpenCV bitwise_and + mask or Segmenting Lungs and nodules in CT images

edited May 23 '17 at 12:19

Community

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answered Dec 16 '13 at 18:02

Martin Beckett

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+1 That's it. I also demonstrate how to use this technique in [this answer](http://stackoverflow.com/a/20288616/176769). – karlphillip Dec 16 '13 at 18:41
@karlphillip, thanks search didn't turn up your title! – Martin Beckett Dec 16 '13 at 18:47

Crop an ellipse form from an image instead of drawing it inside in OpenCV

1 Answers1