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Is there something wrong with circle grid with patternSize of 4 * 3 ?

asked 2012-12-12 20:34:52 -0600

wzx gravatar image

updated 2012-12-13 10:38:20 -0600

Hi, the findCirclesGrid() can detect the circle center points with symmetrical patternSize of 16 * 8, which is shown as follow:

image description

However, I fail to use this function to deal with the symmetrical patternSize of 4 * 3, which is shown as follow:

image description

Could someone tell me how to detect the circle points in patternSize of 4 * 3 ? Thanks!

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answered 2012-12-13 10:36:47 -0600


I can reproduce your problem and indeed the second grid is not detected with the default method. You can use the second available method as a workaround. The code becomes like this:

findCirclesGrid(image, patternSize, centers, CALIB_CB_SYMMETRIC_GRID + CALIB_CB_CLUSTERING)

The 4x3 grid was detected in this case.

P.S. It seems to be a bug that the grid was not detected initially so please fill in a bug report at

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Thank you very much for your kind help! With the method you suggested I succeed to detect the 4x3 grid.

By debugging for a lot of times, I find the ‘minDensity’, a member variable defined in class ‘CirclesGridFinderParameters’, has a default initial value of 10, which is a little big for my case of 4x3 grid. I reset this value to 5, and the default method of ‘findCirclesGrid()’ detected the 4x3 grid of circle successfully.

Therefore, the main reason for the problem is that I have not set a reasonable value for some parameter defined in class ‘CirclesGridFinderParameters’, and it has nothing to do with the ‘findCirclesGrid()’.

Thanks again!

wzx gravatar imagewzx ( 2012-12-13 20:54:06 -0600 )edit

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Asked: 2012-12-12 20:34:52 -0600

Seen: 5,235 times

Last updated: Dec 13 '12