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.

CONTENTS

• About this Project
• Download & Instructions
• License
• The QR_HOBO_CODES
• Acknowledgments
• Keywords

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 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").

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.

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.