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bobbiechen
I'm a big fan of the $1 Unistroke Recognizer - it's just so cool that it works so well with minimal training. I was itching for a reason to use it and threw it into a flag semaphore decoder. Then I realized it was completely the wrong tool for drawings with only (8 choose 2) combinations where rotation does matter, and did something else instead. So, I'm still itching for a good reason to use it.
belugacat
Very cool! I think the name is a reference to the 1€ filter?

https://cristal.univ-lille.fr/~casiez/1euro/

vanderZwan
It's the other way around, says so on the page you linked
CiTyBear
It is the opposite. As state on the website you liked: > The name "1€" is an homage to the $1 recognizer.
jl6
Where did the name $1 come from?
MawKKe
I believe it is a reference to the US dollar
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tantalor
Because this software cost about dollar to make (it sucks).
yread
I wonder if you could make a brain stroke recognizer by filming someone's face and look for one sided paralysis that often comes with it
iamtedd
Is this a joke? A stroke recogniser, and they decided to go with a gesture that looks like a ball-bag?
rbinv
Cool. Those examples remind me of Palm OS' Graffiti (which worked really well at the time): https://en.wikipedia.org/wiki/Graffiti_(Palm_OS)
obrajesse
There's a good reason for that. Graffiti was....derivative of Unistroke, which was developed at PARC as, IIRC, part of the Parctab project. Xerox even sued.

https://news.ycombinator.com/item?id=12310029

Fun fact: You can implement a "classic" Unistroke recognizer just by dividing the character up into quadrants. Every glyph had a unique sequence of quadrant traversals. http://www.yorku.ca/mack/ExperimentSoftware/javadoc/ca/yorku...

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hellbannedguy
It's to bad Palm was run into the ground.

I really liked their products on so many levels, especially the build quality. I thought they would be around forever.

mdp2021
Sorry, correction: «which works really well right now». I still use Graffiti, on Android, as the only keyboard on almost all of my devices. (Exceptions are relevant to technical constraints - no touch, low framerate screens etc.)
greencore
Is it hard to make it recognize mirror strokes?
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Gys
It only works if the starting point of a gesture is as expected. If I start a rectangle in the top right corner then it is characterized as a caret. Only a start in the top left results in a rectangle.
bobbiechen
Right, this is expected. I would think of a "gesture" as a series of points over time (relative to the starting point) - it is path dependent, so a clockwise circle is recognized differently from a counter-clockwise circle.

The paper (citation 11 for the $1 version) goes into more detail. One neat feature is rotation invariance, where you can draw a tilted version and still have it be recognized.

Tuna-Fish
I added a second rectangle as an example starting from a different point, and it never misrecognized any of my rectangles for carets or square brackets again.
RantyDave
Likewise, I added a circle going the "other way" and it got it every time. Cool piece of code, eh?
airstrike
Adding left and right parenthesis started messing up with the square brackets, but then I added a couple more of each square and round brackets and it worked perfectly.

Differentiating from lowercase y and g was next to impossible, though...

ziml77
I was disappointed by that at first too, but then remembered that it says it detects gestures. A gesture is a series of motions, not the final shape.
horsawlarway
This varied a lot for me during testing - It looks like it's actually comparing rotations of the gesture to find a match

It would nail the zigzag and most of the star/box shapes even if I intentionally started in a different place (Very first thing I tested, I'm left handed and start characters/shapes in different places)

It did not handle shapes that are rotationally similar - ex: right square bracket starting from the bottom is always detected as left square bracket, probably because the gesture matches the left bracket, rotated 180 degrees.

It also flubs arrows going right to left (they always come up as v for me)

scotty79
It's more about not where you start and how rotated is what you are drawing, but rather about if you are drawing it clock-wise or counter clock-wise.
skrebbel
It took me long to figure out that this wasn't a one dollar piece of hardware.
hathym
HN challenge: draw a circle! (no matter how hard I tried, it's always a triangle for me)
ihalip
For me, it says rectangle when my "circle" looks more like an elipse.
xxs
1st thing[0]. I didn't seem hard (and I am exceptionally bad at drawing anything, incl. circles with pen and paper):

[0]: https://imgur.com/a/wfyoPLF

ramtatatam
Draw a circle with multiple turns :)
MoD411
It should recognize a single stroke house :)
dvh
Doesn't work for 7 bridges problem :(
ygra
You can add your own shapes.
NiceWayToDoIT
When drawing circle slow always says it is 'rectangle' ?
W0lf
This breaks pretty easy unfortunately by simply drawing in reverse (e.g. draw circle counter-clockwise instead of clockwise etc.)
pjc50
That's a different stroke! Of course it shouldn't match.
StavrosK
Yeah but you know what they say about different folks.
mhandley
That's true, but you can always add the reverse circle as a second example, and then it's happy with either.
maury91
They all need to be drawn in the same direction of the demo. If I draw them in the opposite direction ( example the circle instead of counter-clockwise, I draw it clockwise ), another shape is recognised:

Triangle -> Delete / Caret

X -> Delete

Rectangle -> Caret

Circle -> Caret

Check -> Right square bracket / Arrow

Caret -> V

Zig-zag -> Zig-zag

Arrow -> V

Left square bracket -> Right square bracket

Right square bracket -> Left square bracket

V -> Caret

Delete -> X

Left curly bracket -> Right curly bracket

Right curly bracket -> Left curly bracket

Star -> Left curly bracket / Delete

Pigtail -> Delete

leoedin
When I was a teenager playing Dr Kawashima's Brain Training on DS, I had to completely change how I drew my 9s in order to get it to recognise them (it turned out I started in the wrong place for it to recognise the number).

I only played that game for a month or two, but it stuck with me and now more than a decade later I still draw my 9s differently.

lopis
Well, it's not magic. It probably recognizes direction of strokes. I imagine that you can start from scratch and train both directions to be valid, but then you will find more mismatches.
jzer0cool
Thought "at first" a medical device.

So I drew a heart.

Drawn clockwise, I get a carrot :).

So now I know what to send to my loved ones.

Drawn counter-clockwise, I get a square. And maybe where the carrot will be left to be.

jmiskovic
Now I want editor that shows carrot in place of caret.
chrisxcross
I used it to integrate sketching into a web-based diagram editor ~10 years ago and it was a breeze. OK, I had to train it myself. But it takes only minutes to draw all the shape variants needed. In practice I used 6 shapes and about 5 variants per shape. I conducted a usability test and the $1 recognizer only failed to recognizes the sketches 2-3 times out of ~300 shapes drawn by different users with no additional training.
kuroguro
It keeps telling me my curly brackets are square :/
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peey
I expected it to cost $1, and then I thought "I'd gladly pay $1 for a perpetual licence to a good quality library".

Setting aside OSI's definition of OSS, has this been explored as a OSS funding model?

porlune
This might be obvious to everyone but me, but how do you read "$1" in this context? Do I read it as "one-dollar", or "dollar-sign one", something else? Thank you in advance
Hnaomyiph
I read it as “one-dollar” and assume most people would read it the same. Although I’d prefer if writing rules put the $ after the number; eg 1$.
bionoid
My interpretation is $1 reads as "unistroke"/"singlestroke" while $N = "multistroke"
occamrazor
Does it work on on iPad? Both using finger and pen it scrolls rather then drawing.
ToJans
I recall experimenting with similar approaches about 2 decades ago; depending on your gestures you can actually simplify a lot:

- normalize the draw height/width

- use polar coordinates before normalizing

- normalize the length of the drawn path

- DAG to recognize shapes faster, using partial paths

- only taking into account corners with angles over a certain treshold

- ...

The possibilities are endless, and this is a good exercise to explain that slight alterations on your problem space can have a huge impact on your solution space.

[update - formatting]