Chess board image generation doesn't match the parameters

[jlunder]

When running calibration, the chessboard image generator generates an image that is the wrong size for the entered parameters, preventing calibration. The image should be 1 square larger than the entered numbers in each axis (or the calibration should pass the values through 1 smaller to OpenCV).

E.g., if I have an 8x8 standard chessboard, OpenCV wants this described as a 7x7 calibration target. So if I've entered 8x8 into the dialog, either it should generate a 9x9 image and pass 8x8 into OpenCV, or generate an 8x8 image and pass 7x7 into OpenCV -- otherwise one can spend a lot of time trying to calibrate, wondering if the lighting is wrong, or the angle, or maybe the printing wasn't precise enough, or the target is too wavy...

See https://stackoverflow.com/a/28866120

Also, OpenCV will crash with an assert fail if you pass values smaller than 2x2 into the calibration, so it's probably a good idea to filter the inputs before passing them in.

[matlabbe]

Thanks for reporting. It has been fixed in the commit above. The expected size in the config is the OpenCV one (number of internal corners). Here is an example of a 7x7 chessboard:

or a 8x6: