getuserbarcode
Version:
An advanced barcode-scanner written in JavaScript
386 lines (342 loc) • 10 kB
JavaScript
import BarcodeReader from './barcode_reader';
import {merge} from 'lodash';
function EANReader(opts, supplements) {
opts = merge(getDefaulConfig(), opts);
BarcodeReader.call(this, opts, supplements);
}
function getDefaulConfig() {
var config = {};
Object.keys(EANReader.CONFIG_KEYS).forEach(function(key) {
config[key] = EANReader.CONFIG_KEYS[key].default;
});
return config;
}
var properties = {
CODE_L_START: {value: 0},
CODE_G_START: {value: 10},
START_PATTERN: {value: [1, 1, 1]},
STOP_PATTERN: {value: [1, 1, 1]},
MIDDLE_PATTERN: {value: [1, 1, 1, 1, 1]},
EXTENSION_START_PATTERN: {value: [1, 1, 2]},
CODE_PATTERN: {value: [
[3, 2, 1, 1],
[2, 2, 2, 1],
[2, 1, 2, 2],
[1, 4, 1, 1],
[1, 1, 3, 2],
[1, 2, 3, 1],
[1, 1, 1, 4],
[1, 3, 1, 2],
[1, 2, 1, 3],
[3, 1, 1, 2],
[1, 1, 2, 3],
[1, 2, 2, 2],
[2, 2, 1, 2],
[1, 1, 4, 1],
[2, 3, 1, 1],
[1, 3, 2, 1],
[4, 1, 1, 1],
[2, 1, 3, 1],
[3, 1, 2, 1],
[2, 1, 1, 3]
]},
CODE_FREQUENCY: {value: [0, 11, 13, 14, 19, 25, 28, 21, 22, 26]},
SINGLE_CODE_ERROR: {value: 0.70},
AVG_CODE_ERROR: {value: 0.48},
FORMAT: {value: "ean_13", writeable: false}
};
EANReader.prototype = Object.create(BarcodeReader.prototype, properties);
EANReader.prototype.constructor = EANReader;
EANReader.prototype._decodeCode = function(start, coderange) {
var counter = [0, 0, 0, 0],
i,
self = this,
offset = start,
isWhite = !self._row[offset],
counterPos = 0,
bestMatch = {
error: Number.MAX_VALUE,
code: -1,
start: start,
end: start
},
code,
error;
if (!coderange) {
coderange = self.CODE_PATTERN.length;
}
for ( i = offset; i < self._row.length; i++) {
if (self._row[i] ^ isWhite) {
counter[counterPos]++;
} else {
if (counterPos === counter.length - 1) {
for (code = 0; code < coderange; code++) {
error = self._matchPattern(counter, self.CODE_PATTERN[code]);
if (error < bestMatch.error) {
bestMatch.code = code;
bestMatch.error = error;
}
}
bestMatch.end = i;
if (bestMatch.error > self.AVG_CODE_ERROR) {
return null;
}
return bestMatch;
} else {
counterPos++;
}
counter[counterPos] = 1;
isWhite = !isWhite;
}
}
return null;
};
EANReader.prototype._findPattern = function(pattern, offset, isWhite, tryHarder, epsilon) {
var counter = [],
self = this,
i,
counterPos = 0,
bestMatch = {
error: Number.MAX_VALUE,
code: -1,
start: 0,
end: 0
},
error,
j,
sum;
if (!offset) {
offset = self._nextSet(self._row);
}
if (isWhite === undefined) {
isWhite = false;
}
if (tryHarder === undefined) {
tryHarder = true;
}
if ( epsilon === undefined) {
epsilon = self.AVG_CODE_ERROR;
}
for ( i = 0; i < pattern.length; i++) {
counter[i] = 0;
}
for ( i = offset; i < self._row.length; i++) {
if (self._row[i] ^ isWhite) {
counter[counterPos]++;
} else {
if (counterPos === counter.length - 1) {
sum = 0;
for ( j = 0; j < counter.length; j++) {
sum += counter[j];
}
error = self._matchPattern(counter, pattern);
if (error < epsilon) {
bestMatch.error = error;
bestMatch.start = i - sum;
bestMatch.end = i;
return bestMatch;
}
if (tryHarder) {
for ( j = 0; j < counter.length - 2; j++) {
counter[j] = counter[j + 2];
}
counter[counter.length - 2] = 0;
counter[counter.length - 1] = 0;
counterPos--;
} else {
return null;
}
} else {
counterPos++;
}
counter[counterPos] = 1;
isWhite = !isWhite;
}
}
return null;
};
EANReader.prototype._findStart = function() {
var self = this,
leadingWhitespaceStart,
offset = self._nextSet(self._row),
startInfo;
while (!startInfo) {
startInfo = self._findPattern(self.START_PATTERN, offset);
if (!startInfo) {
return null;
}
leadingWhitespaceStart = startInfo.start - (startInfo.end - startInfo.start);
if (leadingWhitespaceStart >= 0) {
if (self._matchRange(leadingWhitespaceStart, startInfo.start, 0)) {
return startInfo;
}
}
offset = startInfo.end;
startInfo = null;
}
};
EANReader.prototype._verifyTrailingWhitespace = function(endInfo) {
var self = this,
trailingWhitespaceEnd;
trailingWhitespaceEnd = endInfo.end + (endInfo.end - endInfo.start);
if (trailingWhitespaceEnd < self._row.length) {
if (self._matchRange(endInfo.end, trailingWhitespaceEnd, 0)) {
return endInfo;
}
}
return null;
};
EANReader.prototype._findEnd = function(offset, isWhite) {
var self = this,
endInfo = self._findPattern(self.STOP_PATTERN, offset, isWhite, false);
return endInfo !== null ? self._verifyTrailingWhitespace(endInfo) : null;
};
EANReader.prototype._calculateFirstDigit = function(codeFrequency) {
var i,
self = this;
for ( i = 0; i < self.CODE_FREQUENCY.length; i++) {
if (codeFrequency === self.CODE_FREQUENCY[i]) {
return i;
}
}
return null;
};
EANReader.prototype._decodePayload = function(code, result, decodedCodes) {
var i,
self = this,
codeFrequency = 0x0,
firstDigit;
for ( i = 0; i < 6; i++) {
code = self._decodeCode(code.end);
if (!code) {
return null;
}
if (code.code >= self.CODE_G_START) {
code.code = code.code - self.CODE_G_START;
codeFrequency |= 1 << (5 - i);
} else {
codeFrequency |= 0 << (5 - i);
}
result.push(code.code);
decodedCodes.push(code);
}
firstDigit = self._calculateFirstDigit(codeFrequency);
if (firstDigit === null) {
return null;
}
result.unshift(firstDigit);
code = self._findPattern(self.MIDDLE_PATTERN, code.end, true, false);
if (code === null) {
return null;
}
decodedCodes.push(code);
for ( i = 0; i < 6; i++) {
code = self._decodeCode(code.end, self.CODE_G_START);
if (!code) {
return null;
}
decodedCodes.push(code);
result.push(code.code);
}
return code;
};
EANReader.prototype._decode = function() {
var startInfo,
self = this,
code,
result = [],
decodedCodes = [],
resultInfo = {};
startInfo = self._findStart();
if (!startInfo) {
return null;
}
code = {
code: startInfo.code,
start: startInfo.start,
end: startInfo.end
};
decodedCodes.push(code);
code = self._decodePayload(code, result, decodedCodes);
if (!code) {
return null;
}
code = self._findEnd(code.end, false);
if (!code){
return null;
}
decodedCodes.push(code);
// Checksum
if (!self._checksum(result)) {
return null;
}
if (this.supplements.length > 0) {
let ext = this._decodeExtensions(code.end);
if (!ext) {
return null;
}
let lastCode = ext.decodedCodes[ext.decodedCodes.length-1],
endInfo = {
start: lastCode.start + (((lastCode.end - lastCode.start) / 2) | 0),
end: lastCode.end
};
if(!self._verifyTrailingWhitespace(endInfo)) {
return null;
}
resultInfo = {
supplement: ext,
code: result.join("") + ext.code
}
}
return {
code: result.join(""),
start: startInfo.start,
end: code.end,
codeset: "",
startInfo: startInfo,
decodedCodes: decodedCodes,
...resultInfo
};
};
EANReader.prototype._decodeExtensions = function(offset) {
var i,
start = this._nextSet(this._row, offset),
startInfo = this._findPattern(this.EXTENSION_START_PATTERN, start, false, false),
result;
if (startInfo === null) {
return null;
}
for (i = 0; i < this.supplements.length; i++) {
result = this.supplements[i].decode(this._row, startInfo.end);
if (result !== null) {
return {
code: result.code,
start,
startInfo,
end: result.end,
codeset: "",
decodedCodes: result.decodedCodes
}
}
}
return null;
};
EANReader.prototype._checksum = function(result) {
var sum = 0, i;
for ( i = result.length - 2; i >= 0; i -= 2) {
sum += result[i];
}
sum *= 3;
for ( i = result.length - 1; i >= 0; i -= 2) {
sum += result[i];
}
return sum % 10 === 0;
};
EANReader.CONFIG_KEYS = {
supplements: {
'type': 'arrayOf(string)',
'default': [],
'description': 'Allowed extensions to be decoded (2 and/or 5)'
}
};
export default (EANReader);