quagga
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An advanced barcode-scanner written in JavaScript
252 lines (225 loc) • 7.91 kB
JavaScript
import BarcodeReader from './barcode_reader';
import ArrayHelper from '../common/array_helper';
function Code93Reader() {
BarcodeReader.call(this);
}
const ALPHABETH_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%abcd*";
var properties = {
ALPHABETH_STRING: {value: ALPHABETH_STRING},
ALPHABET: {value: ALPHABETH_STRING.split('').map(char => char.charCodeAt(0))},
CHARACTER_ENCODINGS: {value: [
0x114, 0x148, 0x144, 0x142, 0x128, 0x124, 0x122, 0x150, 0x112, 0x10A,
0x1A8, 0x1A4, 0x1A2, 0x194, 0x192, 0x18A, 0x168, 0x164, 0x162, 0x134,
0x11A, 0x158, 0x14C, 0x146, 0x12C, 0x116, 0x1B4, 0x1B2, 0x1AC, 0x1A6,
0x196, 0x19A, 0x16C, 0x166, 0x136, 0x13A, 0x12E, 0x1D4, 0x1D2, 0x1CA,
0x16E, 0x176, 0x1AE, 0x126, 0x1DA, 0x1D6, 0x132, 0x15E
]},
ASTERISK: {value: 0x15E},
FORMAT: {value: "code_93", writeable: false}
};
Code93Reader.prototype = Object.create(BarcodeReader.prototype, properties);
Code93Reader.prototype.constructor = Code93Reader;
Code93Reader.prototype._decode = function() {
var self = this,
counters = [0, 0, 0, 0, 0, 0],
result = [],
start = self._findStart(),
decodedChar,
lastStart,
pattern,
nextStart;
if (!start) {
return null;
}
nextStart = self._nextSet(self._row, start.end);
do {
counters = self._toCounters(nextStart, counters);
pattern = self._toPattern(counters);
if (pattern < 0) {
return null;
}
decodedChar = self._patternToChar(pattern);
if (decodedChar < 0){
return null;
}
result.push(decodedChar);
lastStart = nextStart;
nextStart += ArrayHelper.sum(counters);
nextStart = self._nextSet(self._row, nextStart);
} while (decodedChar !== '*');
result.pop();
if (!result.length) {
return null;
}
if (!self._verifyEnd(lastStart, nextStart, counters)) {
return null;
}
if (!self._verifyChecksums(result)) {
return null;
}
result = result.slice(0, result.length - 2);
if ((result = self._decodeExtended(result)) === null) {
return null;
};
return {
code: result.join(""),
start: start.start,
end: nextStart,
startInfo: start,
decodedCodes: result
};
};
Code93Reader.prototype._verifyEnd = function(lastStart, nextStart) {
if (lastStart === nextStart || !this._row[nextStart]) {
return false;
}
return true;
};
Code93Reader.prototype._patternToChar = function(pattern) {
var i,
self = this;
for (i = 0; i < self.CHARACTER_ENCODINGS.length; i++) {
if (self.CHARACTER_ENCODINGS[i] === pattern) {
return String.fromCharCode(self.ALPHABET[i]);
}
}
return -1;
};
Code93Reader.prototype._toPattern = function(counters) {
const numCounters = counters.length;
let pattern = 0;
let sum = 0;
for (let i = 0; i < numCounters; i++) {
sum += counters[i];
}
for (let i = 0; i < numCounters; i++) {
let normalized = Math.round(counters[i] * 9 / sum);
if (normalized < 1 || normalized > 4) {
return -1;
}
if ((i & 1) === 0) {
for (let j = 0; j < normalized; j++) {
pattern = (pattern << 1) | 1;
}
} else {
pattern <<= normalized;
}
}
return pattern;
};
Code93Reader.prototype._findStart = function() {
var self = this,
offset = self._nextSet(self._row),
patternStart = offset,
counter = [0, 0, 0, 0, 0, 0],
counterPos = 0,
isWhite = false,
i,
j,
whiteSpaceMustStart;
for ( i = offset; i < self._row.length; i++) {
if (self._row[i] ^ isWhite) {
counter[counterPos]++;
} else {
if (counterPos === counter.length - 1) {
// find start pattern
if (self._toPattern(counter) === self.ASTERISK) {
whiteSpaceMustStart = Math.floor(Math.max(0, patternStart - ((i - patternStart) / 4)));
if (self._matchRange(whiteSpaceMustStart, patternStart, 0)) {
return {
start: patternStart,
end: i
};
}
}
patternStart += counter[0] + counter[1];
for ( j = 0; j < 4; j++) {
counter[j] = counter[j + 2];
}
counter[4] = 0;
counter[5] = 0;
counterPos--;
} else {
counterPos++;
}
counter[counterPos] = 1;
isWhite = !isWhite;
}
}
return null;
};
Code93Reader.prototype._decodeExtended = function(charArray) {
const length = charArray.length;
const result = [];
for (let i = 0; i < length; i++) {
const char = charArray[i];
if (char >= 'a' && char <= 'd') {
if (i > (length - 2)) {
return null;
}
const nextChar = charArray[++i];
const nextCharCode = nextChar.charCodeAt(0);
let decodedChar;
switch (char) {
case 'a':
if (nextChar >= 'A' && nextChar <= 'Z') {
decodedChar = String.fromCharCode(nextCharCode - 64);
} else {
return null;
}
break;
case 'b':
if (nextChar >= 'A' && nextChar <= 'E') {
decodedChar = String.fromCharCode(nextCharCode - 38);
} else if (nextChar >= 'F' && nextChar <= 'J') {
decodedChar = String.fromCharCode(nextCharCode - 11);
} else if (nextChar >= 'K' && nextChar <= 'O') {
decodedChar = String.fromCharCode(nextCharCode + 16);
} else if (nextChar >= 'P' && nextChar <= 'S') {
decodedChar = String.fromCharCode(nextCharCode + 43);
} else if (nextChar >= 'T' && nextChar <= 'Z') {
decodedChar = String.fromCharCode(127);
} else {
return null;
}
break;
case 'c':
if (nextChar >= 'A' && nextChar <= 'O') {
decodedChar = String.fromCharCode(nextCharCode - 32);
} else if (nextChar === 'Z') {
decodedChar = ':';
} else {
return null;
}
break;
case 'd':
if (nextChar >= 'A' && nextChar <= 'Z') {
decodedChar = String.fromCharCode(nextCharCode + 32);
} else {
return null;
}
break;
}
result.push(decodedChar);
} else {
result.push(char);
}
}
return result;
};
Code93Reader.prototype._verifyChecksums = function(charArray) {
return this._matchCheckChar(charArray, charArray.length - 2, 20)
&& this._matchCheckChar(charArray, charArray.length - 1, 15);
};
Code93Reader.prototype._matchCheckChar = function(charArray, index, maxWeight) {
const arrayToCheck = charArray.slice(0, index);
const length = arrayToCheck.length;
const weightedSums = arrayToCheck.reduce((sum, char, i) => {
const weight = (((i * -1) + (length - 1)) % maxWeight) + 1;
const value = this.ALPHABET.indexOf(char.charCodeAt(0));
return sum + (weight * value);
}, 0);
const checkChar = this.ALPHABET[(weightedSums % 47)];
return checkChar === charArray[index].charCodeAt(0);
};
export default Code93Reader;