Find chessboard corners with occlusions

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Hi there, Is there a way to find chessboard corners while some of the corners are occluded (by another object or chopped by the image boarders)? Is there an easy way to add this feature (without using "harrisCorner" or other corner detection algorithms)?

E.g. assume a 11x16 chessboard, where the top left corners are outside the image. The basic findChessboardCorners algorithm will fail to find any corner, although it may be useful to show only the ones that were found while the corners that were not found will be set to illegal value or null or something else.

Alternatively, is there a way to find a sub-chessboard? E.g. in an image with 11x16 squares chessboard, calling findChessboardCorners (img, size(9,12), corners) will return a 9x12 chessboard, anywhere (the current findChessboardCorners fails on this one too).

Cheers!