@zxing/library
Version:
TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
76 lines (75 loc) • 3.08 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 BarcodeFormat from '../BarcodeFormat';
import UPCEANReader from './UPCEANReader';
import NotFoundException from '../NotFoundException';
/**
* <p>Implements decoding of the EAN-13 format.</p>
*
* @author dswitkin@google.com (Daniel Switkin)
* @author Sean Owen
* @author alasdair@google.com (Alasdair Mackintosh)
*/
export default class EAN13Reader extends UPCEANReader {
constructor() {
super();
this.decodeMiddleCounters = Int32Array.from([0, 0, 0, 0]);
}
decodeMiddle(row, startRange, resultString) {
let counters = this.decodeMiddleCounters;
counters[0] = 0;
counters[1] = 0;
counters[2] = 0;
counters[3] = 0;
let end = row.getSize();
let rowOffset = startRange[1];
let lgPatternFound = 0;
for (let x = 0; x < 6 && rowOffset < end; x++) {
let bestMatch = UPCEANReader.decodeDigit(row, counters, rowOffset, UPCEANReader.L_AND_G_PATTERNS);
resultString += String.fromCharCode(('0'.charCodeAt(0) + bestMatch % 10));
for (let counter of counters) {
rowOffset += counter;
}
if (bestMatch >= 10) {
lgPatternFound |= 1 << (5 - x);
}
}
resultString = EAN13Reader.determineFirstDigit(resultString, lgPatternFound);
let middleRange = UPCEANReader.findGuardPattern(row, rowOffset, true, UPCEANReader.MIDDLE_PATTERN, new Int32Array(UPCEANReader.MIDDLE_PATTERN.length).fill(0));
rowOffset = middleRange[1];
for (let x = 0; x < 6 && rowOffset < end; x++) {
let bestMatch = UPCEANReader.decodeDigit(row, counters, rowOffset, UPCEANReader.L_PATTERNS);
resultString += String.fromCharCode(('0'.charCodeAt(0) + bestMatch));
for (let counter of counters) {
rowOffset += counter;
}
}
return { rowOffset, resultString };
}
getBarcodeFormat() {
return BarcodeFormat.EAN_13;
}
static determineFirstDigit(resultString, lgPatternFound) {
for (let d = 0; d < 10; d++) {
if (lgPatternFound === this.FIRST_DIGIT_ENCODINGS[d]) {
resultString = String.fromCharCode(('0'.charCodeAt(0) + d)) + resultString;
return resultString;
}
}
throw new NotFoundException();
}
}
EAN13Reader.FIRST_DIGIT_ENCODINGS = [0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A];