@zxing/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
311 lines (310 loc) • 13.3 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.
*/
/*namespace com.google.zxing.oned {*/
import BarcodeFormat from '../BarcodeFormat';
import ChecksumException from '../ChecksumException';
import FormatException from '../FormatException';
import NotFoundException from '../NotFoundException';
import OneDReader from './OneDReader';
import Result from '../Result';
import ResultPoint from '../ResultPoint';
/**
* <p>Decodes Code 39 barcodes. Supports "Full ASCII Code 39" if USE_CODE_39_EXTENDED_MODE is set.</p>
*
* @author Sean Owen
* @see Code93Reader
*/
export default class Code39Reader extends OneDReader {
/**
* Creates a reader that assumes all encoded data is data, and does not treat the final
* character as a check digit. It will not decoded "extended Code 39" sequences.
*/
// public Code39Reader() {
// this(false);
// }
/**
* Creates a reader that can be configured to check the last character as a check digit.
* It will not decoded "extended Code 39" sequences.
*
* @param usingCheckDigit if true, treat the last data character as a check digit, not
* data, and verify that the checksum passes.
*/
// public Code39Reader(boolean usingCheckDigit) {
// this(usingCheckDigit, false);
// }
/**
* Creates a reader that can be configured to check the last character as a check digit,
* or optionally attempt to decode "extended Code 39" sequences that are used to encode
* the full ASCII character set.
*
* @param usingCheckDigit if true, treat the last data character as a check digit, not
* data, and verify that the checksum passes.
* @param extendedMode if true, will attempt to decode extended Code 39 sequences in the
* text.
*/
constructor(usingCheckDigit = false, extendedMode = false) {
super();
this.usingCheckDigit = usingCheckDigit;
this.extendedMode = extendedMode;
this.decodeRowResult = '';
this.counters = new Int32Array(9);
}
decodeRow(rowNumber, row, hints) {
let theCounters = this.counters;
theCounters.fill(0);
this.decodeRowResult = '';
let start = Code39Reader.findAsteriskPattern(row, theCounters);
// Read off white space
let nextStart = row.getNextSet(start[1]);
let end = row.getSize();
let decodedChar;
let lastStart;
do {
Code39Reader.recordPattern(row, nextStart, theCounters);
let pattern = Code39Reader.toNarrowWidePattern(theCounters);
if (pattern < 0) {
throw new NotFoundException();
}
decodedChar = Code39Reader.patternToChar(pattern);
this.decodeRowResult += decodedChar;
lastStart = nextStart;
for (let counter of theCounters) {
nextStart += counter;
}
// Read off white space
nextStart = row.getNextSet(nextStart);
} while (decodedChar !== '*');
this.decodeRowResult = this.decodeRowResult.substring(0, this.decodeRowResult.length - 1); // remove asterisk
// Look for whitespace after pattern:
let lastPatternSize = 0;
for (let counter of theCounters) {
lastPatternSize += counter;
}
let whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
// If 50% of last pattern size, following last pattern, is not whitespace, fail
// (but if it's whitespace to the very end of the image, that's OK)
if (nextStart !== end && (whiteSpaceAfterEnd * 2) < lastPatternSize) {
throw new NotFoundException();
}
if (this.usingCheckDigit) {
let max = this.decodeRowResult.length - 1;
let total = 0;
for (let i = 0; i < max; i++) {
total += Code39Reader.ALPHABET_STRING.indexOf(this.decodeRowResult.charAt(i));
}
if (this.decodeRowResult.charAt(max) !== Code39Reader.ALPHABET_STRING.charAt(total % 43)) {
throw new ChecksumException();
}
this.decodeRowResult = this.decodeRowResult.substring(0, max);
}
if (this.decodeRowResult.length === 0) {
// false positive
throw new NotFoundException();
}
let resultString;
if (this.extendedMode) {
resultString = Code39Reader.decodeExtended(this.decodeRowResult);
}
else {
resultString = this.decodeRowResult;
}
let left = (start[1] + start[0]) / 2.0;
let right = lastStart + lastPatternSize / 2.0;
return new Result(resultString, null, 0, [new ResultPoint(left, rowNumber), new ResultPoint(right, rowNumber)], BarcodeFormat.CODE_39, new Date().getTime());
}
static findAsteriskPattern(row, counters) {
let width = row.getSize();
let rowOffset = row.getNextSet(0);
let counterPosition = 0;
let patternStart = rowOffset;
let isWhite = false;
let patternLength = counters.length;
for (let i = rowOffset; i < width; i++) {
if (row.get(i) !== isWhite) {
counters[counterPosition]++;
}
else {
if (counterPosition === patternLength - 1) {
// Look for whitespace before start pattern, >= 50% of width of start pattern
if (this.toNarrowWidePattern(counters) === Code39Reader.ASTERISK_ENCODING &&
row.isRange(Math.max(0, patternStart - Math.floor((i - patternStart) / 2)), patternStart, false)) {
return [patternStart, i];
}
patternStart += counters[0] + counters[1];
counters.copyWithin(0, 2, 2 + counterPosition - 1);
counters[counterPosition - 1] = 0;
counters[counterPosition] = 0;
counterPosition--;
}
else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw new NotFoundException();
}
// For efficiency, returns -1 on failure. Not throwing here saved as many as 700 exceptions
// per image when using some of our blackbox images.
static toNarrowWidePattern(counters) {
let numCounters = counters.length;
let maxNarrowCounter = 0;
let wideCounters;
do {
let minCounter = 0x7fffffff;
for (let counter of counters) {
if (counter < minCounter && counter > maxNarrowCounter) {
minCounter = counter;
}
}
maxNarrowCounter = minCounter;
wideCounters = 0;
let totalWideCountersWidth = 0;
let pattern = 0;
for (let i = 0; i < numCounters; i++) {
let counter = counters[i];
if (counter > maxNarrowCounter) {
pattern |= 1 << (numCounters - 1 - i);
wideCounters++;
totalWideCountersWidth += counter;
}
}
if (wideCounters === 3) {
// Found 3 wide counters, but are they close enough in width?
// We can perform a cheap, conservative check to see if any individual
// counter is more than 1.5 times the average:
for (let i = 0; i < numCounters && wideCounters > 0; i++) {
let counter = counters[i];
if (counter > maxNarrowCounter) {
wideCounters--;
// totalWideCountersWidth = 3 * average, so this checks if counter >= 3/2 * average
if ((counter * 2) >= totalWideCountersWidth) {
return -1;
}
}
}
return pattern;
}
} while (wideCounters > 3);
return -1;
}
static patternToChar(pattern) {
for (let i = 0; i < Code39Reader.CHARACTER_ENCODINGS.length; i++) {
if (Code39Reader.CHARACTER_ENCODINGS[i] === pattern) {
return Code39Reader.ALPHABET_STRING.charAt(i);
}
}
if (pattern === Code39Reader.ASTERISK_ENCODING) {
return '*';
}
throw new NotFoundException();
}
static decodeExtended(encoded) {
let length = encoded.length;
let decoded = '';
for (let i = 0; i < length; i++) {
let c = encoded.charAt(i);
if (c === '+' || c === '$' || c === '%' || c === '/') {
let next = encoded.charAt(i + 1);
let decodedChar = '\0';
switch (c) {
case '+':
// +A to +Z map to a to z
if (next >= 'A' && next <= 'Z') {
decodedChar = String.fromCharCode(next.charCodeAt(0) + 32);
}
else {
throw new FormatException();
}
break;
case '$':
// $A to $Z map to control codes SH to SB
if (next >= 'A' && next <= 'Z') {
decodedChar = String.fromCharCode(next.charCodeAt(0) - 64);
}
else {
throw new FormatException();
}
break;
case '%':
// %A to %E map to control codes ESC to US
if (next >= 'A' && next <= 'E') {
decodedChar = String.fromCharCode(next.charCodeAt(0) - 38);
}
else if (next >= 'F' && next <= 'J') {
decodedChar = String.fromCharCode(next.charCodeAt(0) - 11);
}
else if (next >= 'K' && next <= 'O') {
decodedChar = String.fromCharCode(next.charCodeAt(0) + 16);
}
else if (next >= 'P' && next <= 'T') {
decodedChar = String.fromCharCode(next.charCodeAt(0) + 43);
}
else if (next === 'U') {
decodedChar = '\0';
}
else if (next === 'V') {
decodedChar = '@';
}
else if (next === 'W') {
decodedChar = '`';
}
else if (next === 'X' || next === 'Y' || next === 'Z') {
decodedChar = '\x7f';
}
else {
throw new FormatException();
}
break;
case '/':
// /A to /O map to ! to , and /Z maps to :
if (next >= 'A' && next <= 'O') {
decodedChar = String.fromCharCode(next.charCodeAt(0) - 32);
}
else if (next === 'Z') {
decodedChar = ':';
}
else {
throw new FormatException();
}
break;
}
decoded += decodedChar;
// bump up i again since we read two characters
i++;
}
else {
decoded += c;
}
}
return decoded;
}
}
Code39Reader.ALPHABET_STRING = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%';
/**
* These represent the encodings of characters, as patterns of wide and narrow bars.
* The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
* with 1s representing "wide" and 0s representing narrow.
*/
Code39Reader.CHARACTER_ENCODINGS = [
0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064,
0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C,
0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016,
0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x0A8,
0x0A2, 0x08A, 0x02A // /-%
];
Code39Reader.ASTERISK_ENCODING = 0x094;