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# qrcode

a qrcode generator in clojure

I was curious how qrcode generation worked so I decided to download the specification pdf and start from scratch with clojure.  This codebase 'works' but I KNOW the scoring/selection for each mask that can be applied to the qrcode is not yet right.  Specifically the algorithm that scores the blocks of similar color (white/black) needs attention.  See the spec for details and feel free to reach out to me if you have a cool implementation for the scoring. :-)

Also, keep in mind, the goal was NOT to write a 'better/faster/cooler' qrcode encoder than what is already out there.  The goal was to simply understand the process and write it in clojure using sequences and a (hopefully) clojure-esque style.  There are lots of places where the code can be improved to be more efficient/faster.  BUT you can watch a qrcode being assembled along the way by examining the data-map that is produced at each step IF you are interested.  Each step returns a map with more added to it so you can monitor what is going on.

Also, it does not do the kanji encoding (but it would not be hard to add).  It only does numeric, alphanumeric, and 8-bit-byte modes.

If you need to generate qrcodes in your code, you are probably better served with one of the supported java libraries that do WAY more than this one
(see http://code.google.com/p/zxing/)

However, if anyone is interested in trying to make this more usable in production, let me know ... it might be fun.

## Usage

The main function is 'encode'.  It takes the message to encode and the error correction level as a keyword (:L :M :Q or :H):

   (requre '[qrcode.core :as qrc])

   (-> (qrc/encode "http://github.com" :L)
       (qrc/draw)
       (qrc/save-as "/tmp/qrcode"))

This would generate a file /tmp/qrcode.png that you should be able to read with your reader.  I know the scoring and selection of the mask is not right but it does work.  The image is generated with 5 px square regions per bit.

The qrc/encode function handles calling each function necessary to make a qrcode but you could call them manually and see the resulting map to see what is happenning.  See the function definition to see each step.

## Things to do

fix the scoring/selection of masks
enhance it to allow different image types (currently only .png)
add kanji mode
add optimizations to allow mixed modes
add colors and other embellishments?
add options for image sizing
add a decoder?

## License

Copyright (C) 2011 pupcus

Distributed under the Eclipse Public License, the same as Clojure.