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asked 2012-09-12 18:41:37 -0500

ninja0524 gravatar image

updated 2012-10-30 23:01:48 -0500

has anyone used findCirclesGrid? I have had no luck using it for a couple of patterns I tried which are pretty easy to detect. the return value is false

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Ilya Lysenkov gravatar imageIlya Lysenkov ( 2012-10-30 23:01:08 -0500 )edit

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answered 2012-10-04 13:08:09 -0500

mgb gravatar image

Width Height must be the correct way around.
For the asymmetrical circle grid on the default target.png w=4 h=11
Not the other way around as printed on the sheet!

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Yes, it is written in the format of a matrix size (the same format is used for a chessboard) and it is stated in the OpenCV documentation:

patternSize = Size(points_per_row, points_per_column)

So in this case it becomes patternSize = Size(4, 11).

Ilya Lysenkov gravatar imageIlya Lysenkov ( 2012-10-04 14:01:11 -0500 )edit

@llya - but it's not terribly clear what is a row and what is a column!

mgb gravatar imagemgb ( 2012-10-10 12:51:35 -0500 )edit

Yeah, I agree, it is not very clear.

Ilya Lysenkov gravatar imageIlya Lysenkov ( 2012-10-10 13:09:21 -0500 )edit

answered 2012-09-13 14:01:54 -0500

Yes, I'm using it with the asymmetric pattern a lot and it works on my images.

Note you have to specify a correct size of the pattern and its type (the first your pattern is asymmetric and the second is symmetric).

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Hi, I use symmetrical circle grid with patternSize of 4 * 3, which are 4 points per row and 3 points per column. However the return value of the findHoles() defined in class CirclesGridFinder is always false. Therefore, the findCirclesGrid() can not find the circle center points with patternSize of 4*3. If I want to detect the circle in symmetrical circle grid with patternSize of 4 * 3, is there any way to solve this problem. Thanks.

wzx gravatar imagewzx ( 2012-12-12 08:51:24 -0500 )edit

This is a strange situation. Could you please send me an example of your images?

Ilya Lysenkov gravatar imageIlya Lysenkov ( 2012-12-12 14:11:03 -0500 )edit

Yes, the images are shown here: Thank you for your attention!

wzx gravatar imagewzx ( 2012-12-12 20:39:16 -0500 )edit

answered 2012-09-13 06:53:23 -0500

Rui Marques gravatar image

updated 2012-10-02 05:57:48 -0500

V.G. gravatar image

Have you tried with the actual circle grid image provided by opencv?

You can find it here for example:

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Is there an svg version of this? The png is badly pixelated and the pattern generator python is very difficult to install on Windows

mgb gravatar imagemgb ( 2012-09-14 09:39:24 -0500 )edit

I do not know of a svg version, sorry.

Rui Marques gravatar imageRui Marques ( 2012-10-02 10:11:42 -0500 )edit

I know that this post is quite old, but I guess this might still be useful to some people. I just found a PDF version of the calibration pattern for different paper sizes:

Carl gravatar imageCarl ( 2015-04-13 17:49:37 -0500 )edit

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Asked: 2012-09-12 18:41:37 -0500

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Last updated: Oct 15 '12