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Re-review of Chess Digitizer, now called Chess Scanner

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A few days ago, I reviewed several Chess related OCR scanners that convert hand

written chess score sheets used in chess tournaments into pgn files that can be

used by chess programs and engines for review. Here was the last article, if

you missed it: https://alaskalinuxuser3.ddns.net/2024/07/12/a-quest-to-find-

the-best-ocr-to-convert-handwritten-score-sheets-to-digital-pgn-files/

One of the apps I reviewed was “Chess Digitizer”. It is a mobile app which was

pretty handy when you consider that with your cell phone, you could review your

games between rounds at a tournament, or do the uploads “on the go”. I am not

really in the app review business, but as the developer reached out to me after

my last review, I felt it was fair and appropriate to review it again with the

latest revision. The developer read my review and pointed out that the version

of the app I was using was several months old, and some of my critique’s have

been resolved. He asked me to consider trying his new app and giving another

honest review. I will note that the app is subscription based, with some parts

of the app being available for free, and some being available to the pro users

who have a subscription. I decided to test it both ways and see how well it

worked. Full disclosure, the developer gave me access to the pro/subscription

version for free to test the app. The app is now called Chess_Scanner.

In any review, there is a subjective part, based on how we feel, and an

objective part, based on facts. I plan to use both of these here, allowing the

reader to draw the best conclusion. However, for the objective test, I am not

sure how fair it is to use the same score sheets again, as in “would my using

and fixing them last time alter the algorithm specific to these samples?” That

I don’t know. To be safe, I did re-run two of the old score sheets, and added

two newer sheets.

Subjective review:

Just as I mentioned in the last post, the GUI for this app is fairly good and

intuitive. I will note that the color scheme for the latest release got even

better, and it looks like a slick product. I like that it shows you the

scoresheet while you are working through the moves, I also really like how easy

it is to tap and change the moves. The layout is good and easy to use while

holding your phone in your hand.

There are very few things about the app that I am not thrilled about. But as it

is a review, I’ll list them here. First, there is a huge gap in usefulness

between the free and pro versions. Essentially the free version is a trial

version to see if you like the app and if it will work with your hand writing.

While both will read your hand writing and make a digital pgn, you can only

download that pgn, or send it to Lichess, Chess.com, etc., with the pro

version. If you have the free version, you can “share” the game by sending

someone a link to the Chess Scan servers, where they can view the game, but

still don’t have access to the pgn. I completely understand, they need a way to

financially support the hardware and software development, but you will have to

pay for the services if you want a tangible pgn that you can copy/paste into

any engine.

I do want to clarify here, all of these applications that I have tried cost

some sort of fee to use, which is appropriate, since they do need to cover the

cost of running their application in the cloud or on their servers. I am not

sure what is the best method for charging the customer, though. Chess Scanner

works on a subscription, once subscribed, it appears you can upload as many

sheets as you want. Other applications, such as pgnApp are based on purchasing

a number of games to upload. For me as a player, I only play in one to four

tournaments a year, so I am not sure a subscription would work well for me.

However, as a tournament director, I have access to 90+ score sheets from a

single tournament. So that would be the better deal. Just depends on your

needs.

Secondly, I got rather used to seeing the board when editing the score sheets

in pgnApp and PawnParse. The screen being smaller on a tablet or phone, I

completely understand their design choice to show you the score sheet and the

editing tools, rather than the board. But sometimes, when a score sheet is not

clear, it helps a simpleton like myself to be able to see the board at this

point in the game, so I can determine if Re7 was Ree7 or Rfe7. Often by looking

at the board and the subsequent moves, it becomes readily clear. Without the

board, I have had to guess a few times and then go back to change my guess,

since that was not the correct guess. I would recommend that the developer

consider having a toggle switch or button so you can somehow view the board in

it’s current position, this would really help with clarity. This is principally

a problem when the score sheet is incorrect, which seems to be 75% of the time

when I upload other people’s scoresheets. (I’m not perfect, but for some reason

I can legibly write the correct moves of the games I have played.)

While great strides have been made in the score sheet alignment department, I

still had one of the four score sheets I tested with that did not line up well

and required several pictures until it got it right. As I will discuss below in

the objective review, I had more trouble with the tablet taking the picture

than with the phone.

And finally, for my regular readers, who typically do not use Google services,

you do have to have Google play services on your phone/tablet to use the pro

version. Seems odd, but that is something I tend to avoid, so to use the pro

version I had to borrow a tablet from my wife to test it. However, that is only

a problem for a niche group of people.

Objective review:

For the objective portion of the review, I fed it several game sheets and just

wrote down the number of half moves and the number of moves it guessed

incorrectly. In my testing, I found no major difference (actually, no

difference noted at all) between the basic (free) and pro (subscription)

version of “Game Generation”, where you choose how you want it to recognize the

hand writing if using a legible score sheet written by someone with good hand

writing. However, it did seem to help when using the pro version for someone

who had terrible hand writing.

Note that the accuracy percentage I am giving to these moves/score sheets is

not the accuracy rating the app gives itself during the recognition process. My

percentage is based on the total number that were correct after refactoring for

each fixed move.

On either the basic or pro version, when I fed it a very legible score sheet,

written in my own hand at one of my games, it recognized all the characters and

gave me a proposed pgn with only 1 move that was in error of what I had

written. That means it correctly interpreted 50 out of 51 half moves, or 98%

accuracy. I then fed it another of my hand written score sheets where it

correctly interpreted 99 out of 100 half moves, or 99% accuracy.

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That said, I fed it the dreaded sample sheet #2 from the previous post, which

before it could not read at all (the hand writing is good, but the score sheet

is a half sheet/small sized sheet. This time my results varied. With my tablet,

Chess Scanner was only able to read the last column of moves, no matter how

many times I took the picture. In a game of 41 moves, it could only read the

last 11, none of which were legal without the first 30, so it did not do well.

Then I tried the same score sheet with my cell phone, and it was able to read

the score sheet with 12 errors for 82 half moves, or 85% accuracy. Again, the

hand writing was perfectly legible, just the scoresheet had small boxes for the

moves. Is this an app problem or a hardware camera problem? I’m not really

sure.

I would like to note, though, that it also read the bottom of the page as part

of the moves. (Please see the picture.)

I then fed it the challenge score sheet #3 from the previous post, which has

103 half moves, 6 known errors, and very bad hand writing. Using the pro

version, it got an impressive 80% of the moves correct, which was objectively

better than the competitors last time, having only 19 failures of recognizing

the moves or characters. I don’t have access to the software, but I think a big

factor in determination seems to be forcing legal moves. If the moves of the

game were legal, then it does pretty good at figuring out what move must be

next.

Conclusion:

Overall, I am really glad that the developer reached out to me for a second

look at this app. It had been updated and improved since the version I tested

before, and it is a really great app. The interface is really good, and it did

exceptionally well with good hand writing, and really good with poor hand

writing. I could see someone using this between rounds at a tournament to see

what went well/wrong in their last game, and making it quick to share your

games online with friends. This app seems best suited for the player,

especially an active one. As a tournament director, I would probably rather

crunch 20 to 90 score sheets on a computer with a mouse and keyboard, but this

is a really handy tool to have in your pocket.

Linux – Keep it simple.