getuserbarcode
Version:
An advanced barcode-scanner written in JavaScript
289 lines (248 loc) • 7.95 kB
JavaScript
import BarcodeReader from './barcode_reader';
function CodabarReader() {
BarcodeReader.call(this);
this._counters = [];
}
var properties = {
ALPHABETH_STRING: {value: "0123456789-$:/.+ABCD"},
ALPHABET: {value: [48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 45, 36, 58, 47, 46, 43, 65, 66, 67, 68]},
CHARACTER_ENCODINGS: {value: [0x003, 0x006, 0x009, 0x060, 0x012, 0x042, 0x021, 0x024, 0x030, 0x048, 0x00c, 0x018,
0x045, 0x051, 0x054, 0x015, 0x01A, 0x029, 0x00B, 0x00E]},
START_END: {value: [0x01A, 0x029, 0x00B, 0x00E]},
MIN_ENCODED_CHARS: {value: 4},
MAX_ACCEPTABLE: {value: 2.0},
PADDING: {value: 1.5},
FORMAT: {value: "codabar", writeable: false}
};
CodabarReader.prototype = Object.create(BarcodeReader.prototype, properties);
CodabarReader.prototype.constructor = CodabarReader;
CodabarReader.prototype._decode = function() {
var self = this,
result = [],
start,
decodedChar,
pattern,
nextStart,
end;
this._counters = self._fillCounters();
start = self._findStart();
if (!start) {
return null;
}
nextStart = start.startCounter;
do {
pattern = self._toPattern(nextStart);
if (pattern < 0) {
return null;
}
decodedChar = self._patternToChar(pattern);
if (decodedChar < 0){
return null;
}
result.push(decodedChar);
nextStart += 8;
if (result.length > 1 && self._isStartEnd(pattern)) {
break;
}
} while (nextStart < self._counters.length);
// verify end
if ((result.length - 2) < self.MIN_ENCODED_CHARS || !self._isStartEnd(pattern)) {
return null;
}
// verify end white space
if (!self._verifyWhitespace(start.startCounter, nextStart - 8)){
return null;
}
if (!self._validateResult(result, start.startCounter)){
return null;
}
nextStart = nextStart > self._counters.length ? self._counters.length : nextStart;
end = start.start + self._sumCounters(start.startCounter, nextStart - 8);
return {
code: result.join(""),
start: start.start,
end: end,
startInfo: start,
decodedCodes: result
};
};
CodabarReader.prototype._verifyWhitespace = function(startCounter, endCounter) {
if ((startCounter - 1 <= 0)
|| this._counters[startCounter - 1] >= (this._calculatePatternLength(startCounter) / 2.0)) {
if ((endCounter + 8 >= this._counters.length)
|| this._counters[endCounter + 7] >= (this._calculatePatternLength(endCounter) / 2.0)) {
return true;
}
}
return false;
};
CodabarReader.prototype._calculatePatternLength = function(offset) {
var i,
sum = 0;
for (i = offset; i < offset + 7; i++) {
sum += this._counters[i];
}
return sum;
};
CodabarReader.prototype._thresholdResultPattern = function(result, startCounter){
var self = this,
categorization = {
space: {
narrow: { size: 0, counts: 0, min: 0, max: Number.MAX_VALUE},
wide: {size: 0, counts: 0, min: 0, max: Number.MAX_VALUE}
},
bar: {
narrow: { size: 0, counts: 0, min: 0, max: Number.MAX_VALUE},
wide: { size: 0, counts: 0, min: 0, max: Number.MAX_VALUE}
}
},
kind,
cat,
i,
j,
pos = startCounter,
pattern;
for (i = 0; i < result.length; i++){
pattern = self._charToPattern(result[i]);
for (j = 6; j >= 0; j--) {
kind = (j & 1) === 2 ? categorization.bar : categorization.space;
cat = (pattern & 1) === 1 ? kind.wide : kind.narrow;
cat.size += self._counters[pos + j];
cat.counts++;
pattern >>= 1;
}
pos += 8;
}
["space", "bar"].forEach(function(key) {
var newkind = categorization[key];
newkind.wide.min =
Math.floor((newkind.narrow.size / newkind.narrow.counts + newkind.wide.size / newkind.wide.counts) / 2);
newkind.narrow.max = Math.ceil(newkind.wide.min);
newkind.wide.max = Math.ceil((newkind.wide.size * self.MAX_ACCEPTABLE + self.PADDING) / newkind.wide.counts);
});
return categorization;
};
CodabarReader.prototype._charToPattern = function(char) {
var self = this,
charCode = char.charCodeAt(0),
i;
for (i = 0; i < self.ALPHABET.length; i++) {
if (self.ALPHABET[i] === charCode){
return self.CHARACTER_ENCODINGS[i];
}
}
return 0x0;
};
CodabarReader.prototype._validateResult = function(result, startCounter) {
var self = this,
thresholds = self._thresholdResultPattern(result, startCounter),
i,
j,
kind,
cat,
size,
pos = startCounter,
pattern;
for (i = 0; i < result.length; i++) {
pattern = self._charToPattern(result[i]);
for (j = 6; j >= 0; j--) {
kind = (j & 1) === 0 ? thresholds.bar : thresholds.space;
cat = (pattern & 1) === 1 ? kind.wide : kind.narrow;
size = self._counters[pos + j];
if (size < cat.min || size > cat.max) {
return false;
}
pattern >>= 1;
}
pos += 8;
}
return true;
};
CodabarReader.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;
};
CodabarReader.prototype._computeAlternatingThreshold = function(offset, end) {
var i,
min = Number.MAX_VALUE,
max = 0,
counter;
for (i = offset; i < end; i += 2){
counter = this._counters[i];
if (counter > max) {
max = counter;
}
if (counter < min) {
min = counter;
}
}
return ((min + max) / 2.0) | 0;
};
CodabarReader.prototype._toPattern = function(offset) {
var numCounters = 7,
end = offset + numCounters,
barThreshold,
spaceThreshold,
bitmask = 1 << (numCounters - 1),
pattern = 0,
i,
threshold;
if (end > this._counters.length) {
return -1;
}
barThreshold = this._computeAlternatingThreshold(offset, end);
spaceThreshold = this._computeAlternatingThreshold(offset + 1, end);
for (i = 0; i < numCounters; i++){
threshold = (i & 1) === 0 ? barThreshold : spaceThreshold;
if (this._counters[offset + i] > threshold) {
pattern |= bitmask;
}
bitmask >>= 1;
}
return pattern;
};
CodabarReader.prototype._isStartEnd = function(pattern) {
var i;
for (i = 0; i < this.START_END.length; i++) {
if (this.START_END[i] === pattern) {
return true;
}
}
return false;
};
CodabarReader.prototype._sumCounters = function(start, end) {
var i,
sum = 0;
for (i = start; i < end; i++) {
sum += this._counters[i];
}
return sum;
};
CodabarReader.prototype._findStart = function() {
var self = this,
i,
pattern,
start = self._nextUnset(self._row),
end;
for (i = 1; i < this._counters.length; i++) {
pattern = self._toPattern(i);
if (pattern !== -1 && self._isStartEnd(pattern)) {
// TODO: Look for whitespace ahead
start += self._sumCounters(0, i);
end = start + self._sumCounters(i, i + 8);
return {
start: start,
end: end,
startCounter: i,
endCounter: i + 8
};
}
}
};
export default CodabarReader;