getuserbarcode/src/reader/barcode_reader.js

An advanced barcode-scanner written in JavaScript

import ArrayHelper from '../common/array_helper';

function BarcodeReader(config, supplements) {
    this._row = [];
    this.config = config || {};
    this.supplements = supplements;
    return this;
}

BarcodeReader.prototype._nextUnset = function(line, start) {
    var i;

    if (start === undefined) {
        start = 0;
    }
    for (i = start; i < line.length; i++) {
        if (!line[i]) {
            return i;
        }
    }
    return line.length;
};

BarcodeReader.prototype._matchPattern = function(counter, code, maxSingleError) {
    var i,
        error = 0,
        singleError = 0,
        sum = 0,
        modulo = 0,
        barWidth,
        count,
        scaled;

    maxSingleError = maxSingleError || this.SINGLE_CODE_ERROR || 1;

    for (i = 0; i < counter.length; i++) {
        sum += counter[i];
        modulo += code[i];
    }
    if (sum < modulo) {
        return Number.MAX_VALUE;
    }
    barWidth = sum / modulo;
    maxSingleError *= barWidth;

    for (i = 0; i < counter.length; i++) {
        count = counter[i];
        scaled = code[i] * barWidth;
        singleError = Math.abs(count - scaled) / scaled;
        if (singleError > maxSingleError) {
            return Number.MAX_VALUE;
        }
        error += singleError;
    }
    return error / modulo;
};

BarcodeReader.prototype._nextSet = function(line, offset) {
    var i;

    offset = offset || 0;
    for (i = offset; i < line.length; i++) {
        if (line[i]) {
            return i;
        }
    }
    return line.length;
};

BarcodeReader.prototype._correctBars = function(counter, correction, indices) {
    var length = indices.length,
        tmp = 0;
    while(length--) {
        tmp = counter[indices[length]] * (1 - ((1 - correction) / 2));
        if (tmp > 1) {
            counter[indices[length]] = tmp;
        }
    }
}

BarcodeReader.prototype._matchTrace = function(cmpCounter, epsilon) {
    var counter = [],
        i,
        self = this,
        offset = self._nextSet(self._row),
        isWhite = !self._row[offset],
        counterPos = 0,
        bestMatch = {
            error: Number.MAX_VALUE,
            code: -1,
            start: 0
        },
        error;

    if (cmpCounter) {
        for ( i = 0; i < cmpCounter.length; i++) {
            counter.push(0);
        }
        for ( i = offset; i < self._row.length; i++) {
            if (self._row[i] ^ isWhite) {
                counter[counterPos]++;
            } else {
                if (counterPos === counter.length - 1) {
                    error = self._matchPattern(counter, cmpCounter);

                    if (error < epsilon) {
                        bestMatch.start = i - offset;
                        bestMatch.end = i;
                        bestMatch.counter = counter;
                        return bestMatch;
                    } else {
                        return null;
                    }
                } else {
                    counterPos++;
                }
                counter[counterPos] = 1;
                isWhite = !isWhite;
            }
        }
    } else {
        counter.push(0);
        for ( i = offset; i < self._row.length; i++) {
            if (self._row[i] ^ isWhite) {
                counter[counterPos]++;
            } else {
                counterPos++;
                counter.push(0);
                counter[counterPos] = 1;
                isWhite = !isWhite;
            }
        }
    }

    // if cmpCounter was not given
    bestMatch.start = offset;
    bestMatch.end = self._row.length - 1;
    bestMatch.counter = counter;
    return bestMatch;
};

BarcodeReader.prototype.decodePattern = function(pattern) {
    var self = this,
        result;

    self._row = pattern;
    result = self._decode();
    if (result === null) {
        self._row.reverse();
        result = self._decode();
        if (result) {
            result.direction = BarcodeReader.DIRECTION.REVERSE;
            result.start = self._row.length - result.start;
            result.end = self._row.length - result.end;
        }
    } else {
        result.direction = BarcodeReader.DIRECTION.FORWARD;
    }
    if (result) {
        result.format = self.FORMAT;
    }
    return result;
};

BarcodeReader.prototype._matchRange = function(start, end, value) {
    var i;

    start = start < 0 ? 0 : start;
    for (i = start; i < end; i++) {
        if (this._row[i] !== value) {
            return false;
        }
    }
    return true;
};

BarcodeReader.prototype._fillCounters = function(offset, end, isWhite) {
    var self = this,
        counterPos = 0,
        i,
        counters = [];

    isWhite = (typeof isWhite !== 'undefined') ? isWhite : true;
    offset = (typeof offset !== 'undefined') ? offset : self._nextUnset(self._row);
    end = end || self._row.length;

    counters[counterPos] = 0;
    for (i = offset; i < end; i++) {
        if (self._row[i] ^ isWhite) {
            counters[counterPos]++;
        } else {
            counterPos++;
            counters[counterPos] = 1;
            isWhite = !isWhite;
        }
    }
    return counters;
};

BarcodeReader.prototype._toCounters = function(start, counter) {
    var self = this,
        numCounters = counter.length,
        end = self._row.length,
        isWhite = !self._row[start],
        i,
        counterPos = 0;

    ArrayHelper.init(counter, 0);

    for ( i = start; i < end; i++) {
        if (self._row[i] ^ isWhite) {
            counter[counterPos]++;
        } else {
            counterPos++;
            if (counterPos === numCounters) {
                break;
            } else {
                counter[counterPos] = 1;
                isWhite = !isWhite;
            }
        }
    }

    return counter;
};

Object.defineProperty(BarcodeReader.prototype, "FORMAT", {
    value: 'unknown',
    writeable: false
});

BarcodeReader.DIRECTION = {
    FORWARD: 1,
    REVERSE: -1
};

BarcodeReader.Exception = {
    StartNotFoundException: "Start-Info was not found!",
    CodeNotFoundException: "Code could not be found!",
    PatternNotFoundException: "Pattern could not be found!"
};

BarcodeReader.CONFIG_KEYS = {};

export default BarcodeReader;