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Barcode recognition with JavaScript - Demo: http://bit.ly/djvUoy

View get_barcode_from_image.js
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/*
* Copyright (c) 2010 Tobias Schneider
* This script is freely distributable under the terms of the MIT license.
*/
 
(function(){
var UPC_SET = {
"3211": '0',
"2221": '1',
"2122": '2',
"1411": '3',
"1132": '4',
"1231": '5',
"1114": '6',
"1312": '7',
"1213": '8',
"3112": '9'
};
getBarcodeFromImage = function(imgOrId){
var doc = document,
img = "object" == typeof imgOrId ? imgOrId : doc.getElementById(imgOrId),
canvas = doc.createElement("canvas"),
width = img.width,
height = img.height,
ctx = canvas.getContext("2d"),
spoints = [1, 9, 2, 8, 3, 7, 4, 6, 5],
numLines = spoints.length,
slineStep = height / (numLines + 1),
round = Math.round;
canvas.width = width;
canvas.height = height;
ctx.drawImage(img, 0, 0);
while(numLines--){
console.log(spoints[numLines]);
var pxLine = ctx.getImageData(0, slineStep * spoints[numLines], width, 2).data,
sum = [],
min = 0,
max = 0;
for(var row = 0; row < 2; row++){
for(var col = 0; col < width; col++){
var i = ((row * width) + col) * 4,
g = ((pxLine[i] * 3) + (pxLine[i + 1] * 4) + (pxLine[i + 2] * 2)) / 9,
s = sum[col];
pxLine[i] = pxLine[i + 1] = pxLine[i + 2] = g;
sum[col] = g + (undefined == s ? 0 : s);
}
}
for(var i = 0; i < width; i++){
var s = sum[i] = sum[i] / 2;
if(s < min){ min = s; }
if(s > max){ max = s; }
}
var pivot = min + ((max - min) / 2),
bmp = [];
for(var col = 0; col < width; col++){
var matches = 0;
for(var row = 0; row < 2; row++){
if(pxLine[((row * width) + col) * 4] > pivot){ matches++; }
}
bmp.push(matches > 1);
}
var curr = bmp[0],
count = 1,
lines = [];
for(var col = 0; col < width; col++){
if(bmp[col] == curr){ count++; }
else{
lines.push(count);
count = 1;
curr = bmp[col];
}
}
var code = '',
bar = ~~((lines[1] + lines[2] + lines[3]) / 3),
u = UPC_SET;
for(var i = 1, l = lines.length; i < l; i++){
if(code.length < 6){ var group = lines.slice(i * 4, (i * 4) + 4); }
else{ var group = lines.slice((i * 4 ) + 5, (i * 4) + 9); }
var digits = [
round(group[0] / bar),
round(group[1] / bar),
round(group[2] / bar),
round(group[3] / bar)
];
code += u[digits.join('')] || u[digits.reverse().join('')] || 'X';
if(12 == code.length){ return code; break; }
}
if(-1 == code.indexOf('X')){ return code || false; }
}
return false;
}
})();
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