I wrote a simple program to automatically draw the heatmap, but it does require manually inputting everyones guesses as coordinates. I used this format for now:
I think for a 19x19 board with more moves it would be a bit of a pain to manually write down everyones guess, so if we want a heatmap for 19x19 boards we should maybe get people to make their guesses on a dedicated page to start with, so we can get them in the right format automatically.
Someone which knows how to do server-end stuff could even show the updated heatmap automatically, but I don’t know how to do that So I would settle for manually making the heatmap in the end, using the guesses which were submitted in some convenient format.
I am actually more curious about how you assign different shades of grey for the blackness stones to different counts of moves in the same spot.
I feel it is quite easy to place all the guessed moves on the same demo board, marked each guessed stone with their count numbers as a collective result, but it wouldn’t look as good as your heatmap.
What if you made a go board tool, which allowed players to play black stones and then outputted such a string as you have in your post?
Then the players could paste that string along with their guess, and you can make a heatmap easily, and the players don’t have to try to format such a string
They could also probably screenshot their guess from that tool in theory
I simply drew all the guesses “on top of” each other, with each black stone being a bit see-through. This was the quickest easiest way to do it, but maybe if I do it again I would first count how many times each stone appears, then assign a color based on that (because the way I did it now, there’s sort of “diminshing returns” on multiple stones in the same spot, a more linear mapping might look better).
Yep, that’s exactly what I was thinking Or maybe even more convenient for the player, have the tool create a custom url which contains the encoded position, so then you just have to share that link (other players can click the link to view the guess, and the host can take the string directly from the url).
Hmm, It also came to me that this might be quite a useful tool for tsumego as well. Adding up all the wrong guesses to see where the most common mistakes are as well as the right responses for key stones
Ok, I threw together the guessing part of the tool we were discussing. Let’s try a test round on it, and then I’ll try to figure out later some convenient way for the host to get automatic scoring and a heatmap from all the submitted links
14 black stones are missing from this board:
Make your guess by clicking the image above, placing any number of black stones (by clicking and/or dragging on the board) and then share your updated URL in a reply here, which should look something like this:
This will let other people look at your guess if they want, and allow the host to semi-automatically score the game and generate a heatmap (once I get around to adding that functionality).
You’re free to do it on a separate board if you want to
Haha, didn’t expect that Fortunately I don’t think it spoils anything (I would assume that most people check some other guesses after submitting their own anyways)… so while I could easily prevent it by adding some randomized digits to each link, I think it’s kind of a nice direct feedback feature
So I would settle for manually making the heatmap in the end, using the guesses which were submitted in some convenient format.
Or maybe even more convenient for the player, have the tool create a custom url which contains the encoded position, so then you just have to share that link (other players can click the link to view the guess, and the host can take the string directly from the url).
Fortunately I don’t think it spoils anything (I would assume that most people check some other guesses after submitting their own anyways)… so while I could easily prevent it by adding some randomized digits to each link, I think it’s kind of a nice direct feedback feature 
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