Chess Scanner (iOS & Android)

WRT signing into Google, some pacakges uses Google backend for things (like if a map app or voice/speech/handwriting recognition), in order for the developer to not pay Google, the user maybe required to sign in (and use his own Google account).

I said "the simplest and cleanest way", there's no mention of the "simplest technique"; frankly, "simplest technique" doesn't even make any sense.

In your example of sorting, the simplest and cleanest way would be to use an appropriate sorting routine from a library. For such few pieces a simple bubble-sort type n^2 comparison is appropriate. Small foot print in memory, storage, and processing.

Anyway, I did do an experiment and it is very doable. I was able to recognize chessboard pieces from pictures (have to be somewhat in-focus, I can also deal with more out-of-focus if I had wanted to, it isn't hard). Accuracy was 100% on my test book.

Here're my steps:

Read color image ->

convert to gray scale ->

uniform the intensity ->

convert to binary (I used Otsu automatic thresholding) ->

correct rotational error (I detect chessboard corners and perform perspective transform; without this step, my accuracy was about 95%) ->

match chessmen patterns (the pattern match uses a mask that covers the chessmen shape)

Using OpenCV, the entire code was about 200 lines.

I can easily add additional chessmen patterns from other books. Even without other book patterns, the program is able to recognize with about 80% accuracy with only this single book's pattern.

NOTE: The above won't work without 2 additional steps for computer screen images due to aliasing between the screen pixels and camera sensor pixels. There probably need to have some low pass filtering and image enhancement. Which isn't all that difficult either.

The above took about 4 hours of programming fun. Most of it was learning OpenCV. I might just add this chess photo of TCBScans -to-FEN feature to my app. It does seem useful.