I always considered barcode scanners as a pice of rocketscience that mere mortals like me aren't able to build. But this weekend megalomania hit me and i wrote one in processing. I didn't use any libraries beside GSVideo (on my linux box) or processing.video (wherever quicktime is available)
My barcodescanner is able to decode a subset of the code128 barcode. it shows all printable characters and it supports all three charsets, but i didn't include all those Bell, Stx, Enq, .. character. feel free to add support for them if you need it :-)
The program assumes that the barcode is placed in the middle of the camera image. It takes the middle row of pixels and converts it to black and white. then it calculates the width of the black and white bars and searches for a barcode startsequence. if it finds one it tries to match the next six bars with the code128 patterns and adds the value of the character that has the highest match to a stringbuffer.
when a stop character is found it calculates the checksum and if that matches it returns the found string (minus the checksum char).
sounds a lot more complicated than it actually is. the hardest part was turning the row of pixels into an array of black and white values.
The code is not really beautifull and it is a bit long because of the big char tables.
click here to download the code.