OpenCV different approach on detecting go board

Question

i am working on an Android app that will recognize a GO board and create a SGF file of it.

i made a version that is able to detect a board and warp the perspective to ma

Answer 1

I'm working on same program. I avoid finding lines at all. First use perspective transform to get the board into a square as you have done. Find the edges of the 19x19 grid. Then assuming the board is 19x19 you can just compute the position of the lines. This works well for me. Then you compute the closest intersection of the center of the stone to determine which row and col line the stone is on. Works pretty well for me. Only probably is calibrating program for different lighting conditions and different color stones and boards.

Answer 2

Assuming that you don't want to "force" your end user to take a cleanest pictures (like using an overlay like some of the QR code scanner for example)

Perhaps you could use some morphological transformations with differents kernels :

• Opening and closing with a rectangular kernel for the lines
• Opening and closing with an ellipse kernel to get the stones (it should be possible to invert the image at some point to get back the white or the black one)

Take a look at http://docs.opencv.org/2.4/doc/tutorials/imgproc/opening_closing_hats/opening_closing_hats.html (sorry this one is in C++ but I think this is almost the same in Java)

I had try these operations to remove a grid from a Sudoku to avoid noise in cell extraction and it worked like a charm.

Let me know of these informations were usefull for you (this is for sure a very interesting case)