@zxing/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
178 lines • 6.78 kB
JavaScript
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import OneDReader from './OneDReader';
import NotFoundException from '../NotFoundException';
import FormatException from '../FormatException';
/**
* <p>Encapsulates functionality and implementation that is common to UPC and EAN families
* of one-dimensional barcodes.</p>
*
* @author dswitkin@google.com (Daniel Switkin)
* @author Sean Owen
* @author alasdair@google.com (Alasdair Mackintosh)
*/
export default class AbstractUPCEANReader extends OneDReader {
constructor() {
super(...arguments);
this.decodeRowStringBuffer = '';
}
// private final UPCEANExtensionSupport extensionReader;
// private final EANManufacturerOrgSupport eanManSupport;
/*
protected UPCEANReader() {
decodeRowStringBuffer = new StringBuilder(20);
extensionReader = new UPCEANExtensionSupport();
eanManSupport = new EANManufacturerOrgSupport();
}
*/
static findStartGuardPattern(row) {
let foundStart = false;
let startRange = null;
let nextStart = 0;
let counters = [0, 0, 0];
while (!foundStart) {
counters = [0, 0, 0];
startRange = AbstractUPCEANReader.findGuardPattern(row, nextStart, false, this.START_END_PATTERN, counters);
let start = startRange[0];
nextStart = startRange[1];
let quietStart = start - (nextStart - start);
if (quietStart >= 0) {
foundStart = row.isRange(quietStart, start, false);
}
}
return startRange;
}
static checkChecksum(s) {
return AbstractUPCEANReader.checkStandardUPCEANChecksum(s);
}
static checkStandardUPCEANChecksum(s) {
let length = s.length;
if (length === 0)
return false;
let check = parseInt(s.charAt(length - 1), 10);
return AbstractUPCEANReader.getStandardUPCEANChecksum(s.substring(0, length - 1)) === check;
}
static getStandardUPCEANChecksum(s) {
let length = s.length;
let sum = 0;
for (let i = length - 1; i >= 0; i -= 2) {
let digit = s.charAt(i).charCodeAt(0) - '0'.charCodeAt(0);
if (digit < 0 || digit > 9) {
throw new FormatException();
}
sum += digit;
}
sum *= 3;
for (let i = length - 2; i >= 0; i -= 2) {
let digit = s.charAt(i).charCodeAt(0) - '0'.charCodeAt(0);
if (digit < 0 || digit > 9) {
throw new FormatException();
}
sum += digit;
}
return (1000 - sum) % 10;
}
static decodeEnd(row, endStart) {
return AbstractUPCEANReader.findGuardPattern(row, endStart, false, AbstractUPCEANReader.START_END_PATTERN, new Array(AbstractUPCEANReader.START_END_PATTERN.length).fill(0));
}
static findGuardPattern(row, rowOffset, whiteFirst, pattern, counters) {
let width = row.getSize();
rowOffset = whiteFirst ? row.getNextUnset(rowOffset) : row.getNextSet(rowOffset);
let counterPosition = 0;
let patternStart = rowOffset;
let patternLength = pattern.length;
let isWhite = whiteFirst;
for (let x = rowOffset; x < width; x++) {
if (row.get(x) !== isWhite) {
counters[counterPosition]++;
}
else {
if (counterPosition === patternLength - 1) {
if (OneDReader.patternMatchVariance(counters, pattern, AbstractUPCEANReader.MAX_INDIVIDUAL_VARIANCE) < AbstractUPCEANReader.MAX_AVG_VARIANCE) {
return [patternStart, x];
}
patternStart += counters[0] + counters[1];
let slice = counters.slice(2, counters.length);
for (let i = 0; i < counterPosition - 1; i++) {
counters[i] = slice[i];
}
counters[counterPosition - 1] = 0;
counters[counterPosition] = 0;
counterPosition--;
}
else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw new NotFoundException();
}
static decodeDigit(row, counters, rowOffset, patterns) {
this.recordPattern(row, rowOffset, counters);
let bestVariance = this.MAX_AVG_VARIANCE;
let bestMatch = -1;
let max = patterns.length;
for (let i = 0; i < max; i++) {
let pattern = patterns[i];
let variance = OneDReader.patternMatchVariance(counters, pattern, AbstractUPCEANReader.MAX_INDIVIDUAL_VARIANCE);
if (variance < bestVariance) {
bestVariance = variance;
bestMatch = i;
}
}
if (bestMatch >= 0) {
return bestMatch;
}
else {
throw new NotFoundException();
}
}
}
// These two values are critical for determining how permissive the decoding will be.
// We've arrived at these values through a lot of trial and error. Setting them any higher
// lets false positives creep in quickly.
AbstractUPCEANReader.MAX_AVG_VARIANCE = 0.48;
AbstractUPCEANReader.MAX_INDIVIDUAL_VARIANCE = 0.7;
/**
* Start/end guard pattern.
*/
AbstractUPCEANReader.START_END_PATTERN = [1, 1, 1];
/**
* Pattern marking the middle of a UPC/EAN pattern, separating the two halves.
*/
AbstractUPCEANReader.MIDDLE_PATTERN = [1, 1, 1, 1, 1];
/**
* end guard pattern.
*/
AbstractUPCEANReader.END_PATTERN = [1, 1, 1, 1, 1, 1];
/**
* "Odd", or "L" patterns used to encode UPC/EAN digits.
*/
AbstractUPCEANReader.L_PATTERNS = [
[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],
];
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