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Yep, it’s a QR code stencil generator! The F.A.T. Lab is pleased to present QR_STENCILER, a free, fully-automated utility which converts QR codes into vector-based stencil patterns suitable for laser-cutting. Additionally, we present QR_HOBO_CODES, a series of one hundred QR stencil designs which, covertly marked in urban spaces, may be used to warn people about danger or clue them into good situations. The QR_STENCILER and the QR_HOBO_CODES join the Adjustable Pie Chart Stencil in our suite of homebrew "infoviz graffiti" tools for locative and situated information display.

The QR_STENCILER loads QR code image files, and exports vector-based PDF stencils.

CONTENTS

ABOUT THIS PROJECT
QR codes are a form of two-dimensional barcode which are widely used to convey URLs and other short texts through camera-based smartphones. A variety of free tools exist to generate QR codes (such as the Google Charts API) and to read them (such as TapMedia’s free QR Reader for iPhone app). Our QR_STENCILER is a Java-based software utility which loads a user-specified QR code image — from which it then generates a lasercutter-ready, topologically correct stencil .PDF. As Fred Trotter has pointed out, QR codes contain stencil islands in unpredictable configurations. QR_STENCILER automatically detects and bridges these islands, using thin lines that are minimally disruptive to the highly robust QR algorithm. It does so through the use of two basic image processing techniques: connected component labeling (sometimes called blob detection) and 8-connected chain coding (sometimes called contour tracing). QR_STENCILER was created with Processing, a free, cross-platform programming toolkit for the arts.

Closeup of stencil corners and islands
Closeup of a QR code lasercut in 1/8"-thick fiberboard. The QR_STENCILER automatically thickens corners between squares (left) and generates "bridges" to connect stencil islands (center). The level (amount) of island bridging is user-adjustable.

Accompanying the QR_STENCILER are the QR_HOBO_CODES (see below), a set of 100 lasercutter-ready QR stencil designs created with the QR_STENCILER software. These stencils can be understood as a covert markup scheme for urban spaces — providing directions, information, and warnings to digital nomads and other indigenterati. We present these as modern equivalents of the chalk-based "hobo signs" developed by 19th century vagabonds and migratory workers to cope with the difficulty of nomadic life. Indeed, our set of QR stencils port a number of classic hobo annotations to the QR format ("turn right here", "dangerous dog", "food for work") as well as some new ones, with a nod to warchalking, that are specific to contemporary conditions ("insecure wifi", "hidden cameras", "vegans beware").

Classic hobo signs
Examples of 19th- and 20th-Century "hobo signs". Sources: Fran DeLorenzo (left), Wikipedia (right).

DOWNLOAD & INSTRUCTIONS
QR_STENCILER has been tested in MacOSX 10.6.8, but (since Processing is a cross-platform toolkit) it should work in Windows or Linux as well.

  1. Make yourself a QR code image which embeds a short piece of text. GoQR.me, Google and Kaywa all provide free online QR generators. To reduce the complexity of the stencil, we recommend generating your code with the shortest possible texts, and with lower levels of error correction (L-level or M-level). At the same time, we recommend generating QR code images with more pixel resolution, such as 500x500px; for QR_STENCILER, the ideal input image has a “grid size” of about 20 image-pixels per QR grid-cell. (See this QR code for an example; it has 23-pixel grid-cells in an overall image size of 540x540px.)
  2. Download QR_STENCILER.zip, and unzip this to a folder. The QR_STENCILER is also available from this Github repository.
  3. Although the zip includes compiled executables for Mac, Windows and Linux, we recommend running the QR_STENCILER from the Processing development environment. Download and install the Processing development tool. The QR_STENCILER works with Processing v.1.5.1 or later.
  4. Put your QR code image in the folder, ‘QR_STENCILER/data/’
  5. Launch Processing and open ‘QR_STENCILER.pde’
  6. Press ‘Run’ (Command-R) to start the stenciler.
  7. You will be prompted to Open your QR code image. (A default “hello world” QR code will be opened if none is provided).
  8. After opening the QR code image, the program will generate a stencil .PDF in the ‘data’ folder. Note that there are some options (checkboxes, sliders) which you can use to alter the generated stencils in various ways, including (for example) generating “reverse” (white-on-black) stencils.
  9. The .PDF can be opened in your favorite CAD program, for laser-cutting materials like cardboard, delrin, MDF or acrylic. If you need to find a lasercutter, consider Ponoko.com, which ships anywhere. You can also Google ‘lasercutting service‘ to find a bureau near you, or check the Architecture or Design departments of your local university. (Of course, you could always print out the PDF on paper if you prefer to cut the stencil by hand. Cheap!)
  10. For non-permanent outdoor marking materials, we recommend Erwin Strait-Line 64908 powdered chalk; black spray chalk; black finger paint; and Crayola Sidewalk Paint.
  11. After marking your stencil, test it with a QR code reader, such as TapMedia’s free QR Reader for iPhone app.

The QR_STENCILER loads QR code image files, and exports vector-based PDF stencils.
More photos: 1, 2, 3, 4, 5.

LICENSE
The QR_STENCILER software is provided "as is", without warranty of any kind. QR_STENCILER is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. You are free to distribute, remix, and modify QR_STENCILER, so long as you share alike and provide attribution to FFFFF.AT. The repackaging of QR_STENCILER as or into commercial software, is expressly prohibited. Please note that QR_STENCILER also enjoys protections under the GRL Repercussions 3.0 license. More details about QR_STENCILER’s license and warranty can be found in the preamble to its main code file, QR_STENCILER.pde; for other uses, please contact us. The 100 QR_HOBO_CODES and their respective stencils are hereby dedicated to the public domain.

QR_HOBO_CODES


25-minute wait
png | stencil

assholes
png | stencil

bad coffee
png | stencil

bad food
png | stencil

bad tempered owner
png | stencil

bad water
png | stencil

be alert
png | stencil

be quiet
png | stencil

be ready to defend yourself
png | stencil

beware pickpockets
png | stencil

bike thieves
png | stencil

boring
png | stencil

broken meter
png | stencil

camera perverts
png | stencil

camp here
png | stencil

cars ticketed
png | stencil

caveat emptor
png | stencil

changing table
png | stencil

cheap drinks
png | stencil

check cashing
png | stencil

civilized place
png | stencil

contraception available
png | stencil

cops active
png | stencil

cops inactive
png | stencil

danger
png | stencil

dangerous homophobes
png | stencil

dangerous neighborhood
png | stencil

dishonest scalpers here
png | stencil

dog
png | stencil

food for work
png | stencil

free doctor
png | stencil

free out-of-date food
png | stencil

free wifi
png | stencil

get out fast
png | stencil

go straight
png | stencil

good cheap food
png | stencil

good coffee
png | stencil

good for a handout
png | stencil

good to kids
png | stencil

good veg-burger
png | stencil

good water
png | stencil

GPS is incorrect
png | stencil

great dumpster
png | stencil

habla espanol
png | stencil

has showers
png | stencil

help if sick
png | stencil

here is the place
png | stencil

hidden cameras
png | stencil

high-fee ATM
png | stencil

hold your tongue
png | stencil

insecure wifi
png | stencil

it’s fake
png | stencil

just ignore him
png | stencil

keep away
png | stencil

keep going
png | stencil

kind family
png | stencil

lax oversight
png | stencil

look down
png | stencil

look up
png | stencil

lots of outlets
png | stencil

mean to children
png | stencil

nice bathroom
png | stencil

no bathrooms
png | stencil

no changing table
png | stencil

no fee ATM
png | stencil

no outlets
png | stencil

no pets
png | stencil

no privacy
png | stencil

open late
png | stencil

over-priced
png | stencil

over-rated
png | stencil

owner gives to GOP
png | stencil

owner has a gun
png | stencil

perverts
png | stencil

pissoir
png | stencil

Plan B sold here
png | stencil

prostitution sting
png | stencil

scammers
png | stencil

sleep in barn
png | stencil

speed trap
png | stencil

stay low
png | stencil

strong phone signal
png | stencil

talk religion
get food

png | stencil

tell a hard luck
story here

png | stencil

test market
png | stencil

those aren’t real
png | stencil

toll road
png | stencil

tramp camp
png | stencil

tramps arrested on sight
png | stencil

turn left here
png | stencil

turn right here
png | stencil

unexpectedly good coffee
png | stencil

unsafe area
png | stencil

use gloves
png | stencil

used frying oil available
png | stencil

vegans beware
png | stencil

well guarded
png | stencil

will give to get
rid of you

png | stencil

work available
png | stencil

worth saving
png | stencil

ACKNOWLEDGMENTS
QR_STENCILER was created by Golan Levin and Asa Foster III with support from the STUDIO for Creative Inquiry at Carnegie Mellon University. Thanks to Ben Fry, Andreas Schlegel, Marcus Beausang, Neil Brown & Judy Robertson for the terrific code they have made available online. A tip of the hat to Fred Trotter, Jovino, Ric Johnson, le Suedois, Patrick Donnelly, David J. Burden, Matt Jones and others who have gone down similar or related paths. Additional thanks to Andrea Boykowycz for creative input. Some of the QR_HOBO_CODES are adapted from or inspired by designs presented elsewhere by Fran DeLorenzo and Cockeyed.com. "QR code" is trademarked by Denso Wave, Inc.

KEYWORDS
Barcode, QR code, stencil, QR code stencil, graffiti, grafitti, graffiti research, graf technology, street art, culture jamming, tactical media, urban messaging, locative media, situated visualization, contextual computing, lasercut, laser cutter, digital fabrication, template, chalk signs, chalk, spray paint, spraypaint, fffffat lab, hobo culture, hobo signs, warchalking.

COMMENTS

  1. Al says:

    Any recommemded sites that will create the lasercut boards?

  2. [...] Here is a link to his post on his new laser-cutter QR code stencil generation code. Along with his first application, a remake of hobo-coding. [...]

  3. golan says:

    Google ‘lasercutting service‘ to find a bureau near you, or check the Architecture or Design departments of your local university.

  4. Apostolos says:

    In your opinion which is the best QR code generator? I’ve tried several ones within the past year, but many provide messed-up & non-readable QRs.

  5. narnua says:

    This is a nice one I use often (other than generating my own with software libraries)
    http://qrcode.kaywa.com/

    For lasercutting you can use ponoko.com, send in your design & shipped anywhere

  6. Apostolos says:

    Narnua, thanks, you’re awesome.

  7. J. says:

    very cool! thanks!

  8. corgimas says:

    You might want to double check your codes/names….looks like some of those codes up there are rearranged…..

  9. [...] The Free Art and Technology Lab have released a free utility which converts QR Codes into vector based stencil patterns suitable for laser cutting. QR_STENCILER solves the Fred Trotter problem of stencil islands by automatically detecting them and bridging the stencil islands with thin lines that have a minimal effect on scanning (image below). The software runs on MacOSX 10.6.8. and is available under a Creative Commons copyright license. [...]

  10. [...] their QR Code stencil pattern generator the Free Art and Technology Lab released a set of 100 laser cutter ready QR stencil designs representing the digital equivalent of chalk-based “hobo signs“. This covert markup [...]

  11. Kieran says:

    This is very cute, and huge kudos for your work, but, some musings…

    How small can you make these can still have them be effective? 1′ square stencils are a little big for the average urbanista, and the size also severely limits the range of stencils one could carry. Could you make them palm-sized and colour them with a sharpie? Or, better still, create some kind of hand-portable, Arduino-based QR graffiti printer (allowing you to leave any QR code you choose at any location)…

  12. golan says:

    @Kieran I’m working on a boxed set of 100 delrin mask sheets, which are 7″x7″. Each cell in the QR codes is around 0.25 – 0.33″, depending on the message. This is just large enough to color in with a sharpie or paint pen, but it’s more convenient to use a small (pocket) spraypaint can, such as Krylon Short Cuts (3oz can) or Duncan Tulip Fabric Spray Paint (2oz can).

  13. golan says:

    @corgimas, is there a specific example which is mis-labeled or mis-linked? The HTML was auto-generated; there “shouldn’t” be any errors. In all cases the text links appears below the corresponding image.

  14. corgimas says:

    I tried running a few of them off the screen with my phone and they came up mixed – but they were other codes on the page, not like the codes did not work at all!!!! Sorry i did not take any notes on them!!!
    r

  15. golan says:

    @Apostolos – As I suggested in the text, I like the Google QR generator, documented at http://code.google.com/apis/chart/image/docs/gallery/qr_codes.html. To generate a QR code with this tool, follow this URL in your browser:
    LINK — then start fiddling with the URL!

  16. golan says:

    @corgimas – I just exhaustively checked the hobo codes; all of the images are correctly labeled and linked. If you point your phone at a page full of different QR codes, however, it’s impossible to guarantee which one of the codes your phone will select to read.

  17. Justin Watt says:

    Golan, neat. Used your code to generate a transparent PNG “stencil” of sorts.

  18. Rich says:

    Do you think its possible to alter the code to work with any 2D 1bit graphics (ie just black / white pixels)?

  19. Timbotron says:

    Here’s a nice collection of early/original hobo signs. Use as you see fit, and enjoy:

    http://supersecretclubhouse.blogspot.com/2011/02/secret-hobo-signs.html

  20. [...] fellow “gentlemen of the countryside”. The finest FATL scientists have come up with a program that generates stencils of QR Codes. The code can be sprayed onto any surface, and can be read by all smartphone-equipped [...]

  21. golan says:

    @Rich – in principle, it would be quite easy to modify my code to produce stencil patterns from arbitrary black-and-white images. However, to produce the best results, the QR_STENCILER relies on the assumptions that (1) the input image consists of axis-aligned squares and rectangles, and (2) that these rectangles are sized according to integer multiples of some basic grid size. The code might still “work” (in some basic sense) if these assumptions are not true. But I would have written the code quite differently if I was dealing with such a general problem.

  22. [...] their QR Code stencil pattern generator the Free Art and Technology Lab released a set of 100 laser cutter ready QR stencil designs representing the digital equivalent of chalk-based “hobo signs“. This covert markup [...]

  23. golan says:

    @narnua, thanks much for your terrific suggestions. I’ve incorporated them into the main blog post.

  24. golan says:

    Geoffrey Dorne has kindly translated the QR_HOBO_CODES into French: http://graphism.fr/les-hobo-signs-de-2011-seront-des-qr-codes-vagabonds-armezvous-de-vos-tlphones/. He’s done a nice job maintaining the idiomatic flavor of the texts :) In his honor I’ll shortly produce a set of French QR stencils.

  25. [...] We present QR_STENCILER, a free, fully-automated utility which converts QR codes into vector-based stencil patterns suitable for laser-cutting. Additionally, we present QR_HOBO_CODES, a series of one hundred QR stencil designs which, covertly marked in urban spaces, may be used to warn people about danger or clue them into good situations.* [...]

  26. narnua says:

    You can also find your local Fablab or hackerspace, most Fablabs and some hackerspaces have lasercutters:
    http://en.wikipedia.org/wiki/Fab_lab
    http://hackerspaces.org/

  27. Bryan Croft says:

    Nice tool ! – im playing with now …and we have 3 laser engravers… hit me up ill make you one for free just to play with the laser :)

  28. [...] (“insecure wifi”, “hidden cameras”, “vegans beware”). Here’s how to install the app, and some samples. We present the design of an adjustable lasercut stencil pattern for pie-chart [...]

  29. [...] ones would call the cops on sight. Now there’s a 21st century version created by New York-based Free Art and Technology Lab —hobo QR codes, those squiggly little boxes you scan with your smartphone. They take the form of [...]

  30. [...] Levin at fffff.at writes: Yep, it’s a QR code stencil generator! We present QR_STENCILER, a free, [...]

  31. Brainspore says:

    Cool idea, I’ve been working on something similar but the software to streamline the process is a huge improvement.

    If I may offer a suggestion, black spray chalk is an easier-to-use alternative to powdered chalk. It’s pretty hard to find compared to white spray chalk but one place that sells it is here: http://artprimo.com/catalog/molotow-chalk-spray-paint-p-1122.html

  32. cool dude! i had a project just like it I put up a few months ago. didn’t have the java program to make it automatically though.

    I had a project just like this, although I didn’t have the java to made the .pdf for me automagicly.

    My nerdbait QR stencil

  33. Golan says:

    @Brainspore – thanks for the tip! Feel free to add a link to your related work if you have a page for it.

  34. [...] codes with messages you might need to go about modern life. Instructions and examples are located on his website (contains some adult [...]

  35. Bryan Croft says:

    wow – thanks for this tool ! we jsut made a few on our laser … took all of 5 minutes :)

  36. [...] in-depth step-by-step process is outlined over at Free Art & Technology (the brilliant minds behind the Media Artist Contingency Plan), but here’s the high-level [...]

  37. [...] Code Stencil Generator of the Day: The folks at fffff.at have created an app that generates a QR code stencil design for any text you choose. Just lasercut and add paint, and [...]

  38. [...] QR_STENCILER and QR_HOBO_CODES The QR_STENCILER is a free, fully-automated utility which converts QR codes into vector-based stencil patterns suitable for laser-cutting. Source: fffff.at [...]

  39. John says:

    I do like this – perhaps clean graffitti could be done doo I’d the stencil is placed in a very green stone surface and is treated with a bleach solution? We’re at http://www.qrcodemaker.co.uk if you want to try us out.

  40. [...] mai întâi să generați un cod QR și pe urmă să intrați aici, unde găsiți tot ce vă trebuie pentru a-l transforma într-un [...]

  41. [...] soft pour créer vos pochoirs est en téléchargement libre sur leur site, disponible à cette adresse. Voici la procédure de [...]

  42. Charles Boisseau says:

    I don’t get it. Say you use the “free wifi” stencil you provided. When I click on that where do i go to learn what the QR code is saying? When a person clicks on your code for free wifi it just shows me the code. It needs to say “Free Wifi” on a smartphone to know what the message is. So your codes need to connect online someplace. How can I see those messages?

  43. Golan says:

    @Charles, in order to decode a QR code image (whether downloaded, stenciled or otherwise), you will need a “QR code reader”, such as an app on your smartphone. When you point the reader’s camera at the QR code, you’ll be able to see the “hidden” text which is embedded in the code.

  44. [...] QR Code Stencil Generator and QR Hobo Codes | F.A.T.Our QR_STENCILER is a Java-based software utility which loads a user-specified QR code image — from which it then generates a lasercutter-ready, topologically correct stencil .PDF [...]

  45. [...] wheel on my Google Reader: scroll, scroll, scroll, scroll. Adding stars to interesting posts like this one, this one and this [...]

  46. Network Geek says:

    What program do you all recommend to read them with on your phone? iPhone or Android, or both, if possible.

    Thanks!

  47. [...] desires a stencil QR code simply has to create a QR code as one would usually do and then upload it into a program that turns the QR code into a file that can be printed by any local company that offers [...]

  48. Jawnita says:

    I love the high/low tech approach, and this project is funny and insightful.

    That said, a peeve: is the transphobic “those aren’t women” one really necessary?

  49. [...] most bizarrely, Golan Levin and Asa Foster III have created QR_HOBO_CODES, a series of one hundred QR stencil designs which when marked in urban spaces, may be used to [...]

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