Draw circle around a white area in OpenCV (C language)

Question

how can I draw a circle around a white space in a image file with OpenCV (C language)?

image example:

thanks a lot!

nimcap · Answer 1 · 2010-03-19T10:40:18.077

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First you can use FindContours to find all (in your case 1) contours (blobs/regions) in the image, then you can draw a circle or any other shape you want around the contour.

Edit: To draw a circle you can use Circle.

edited Mar 19 '10 at 10:40

answered Mar 13 '10 at 18:37

nimcap

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how can I draw any shape around the contour?(where I get the coordinates) – frx08 Mar 18 '10 at 16:25
@frx08: You can use `cvBoundingRect()` to find the coordinates, if I am not mistaken. – nimcap Apr 14 '10 at 15:48

score 1 · Answer 2 · answered Mar 18 '10 at 14:23

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you can compute moments first, then get circle info from it.

answered Mar 18 '10 at 14:23

rcen

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score 0 · Answer 3 · answered Mar 13 '10 at 18:24

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You don't really need opencv for that, you just loop over your image and calculate the bounding box surrounding the white blob, get the center and the radius of your circle is the length from the center to any corner. Then just use GDI or something to draw your circle.

answered Mar 13 '10 at 18:24

Blindy

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in that program I use functions of OpenCV so I think is better use OpenCV that implements also the drawing of a circle – frx08 Mar 13 '10 at 18:35

Draw circle around a white area in OpenCV (C language)

3 Answers3