@zxing/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
336 lines (334 loc) • 13.4 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 DecodeHintType from '../DecodeHintType';
import FormatException from '../FormatException';
import NotFoundException from '../NotFoundException';
import Result from '../Result';
import ResultPoint from '../ResultPoint';
import StringBuilder from '../util/StringBuilder';
import System from '../util/System';
import OneDReader from './OneDReader';
/**
* <p>Decodes ITF barcodes.</p>
*
* @author Tjieco
*/
export default class ITFReader extends OneDReader {
constructor() {
// private static W = 3; // Pixel width of a 3x wide line
// private static w = 2; // Pixel width of a 2x wide line
// private static N = 1; // Pixed width of a narrow line
super(...arguments);
// Stores the actual narrow line width of the image being decoded.
this.narrowLineWidth = -1;
}
// See ITFWriter.PATTERNS
/*
/!**
* Patterns of Wide / Narrow lines to indicate each digit
*!/
*/
decodeRow(rowNumber, row, hints) {
// Find out where the Middle section (payload) starts & ends
let startRange = this.decodeStart(row);
let endRange = this.decodeEnd(row);
let result = new StringBuilder();
ITFReader.decodeMiddle(row, startRange[1], endRange[0], result);
let resultString = result.toString();
let allowedLengths = null;
if (hints != null) {
allowedLengths = hints.get(DecodeHintType.ALLOWED_LENGTHS);
}
if (allowedLengths == null) {
allowedLengths = ITFReader.DEFAULT_ALLOWED_LENGTHS;
}
// To avoid false positives with 2D barcodes (and other patterns), make
// an assumption that the decoded string must be a 'standard' length if it's short
let length = resultString.length;
let lengthOK = false;
let maxAllowedLength = 0;
for (let value of allowedLengths) {
if (length === value) {
lengthOK = true;
break;
}
if (value > maxAllowedLength) {
maxAllowedLength = value;
}
}
if (!lengthOK && length > maxAllowedLength) {
lengthOK = true;
}
if (!lengthOK) {
throw new FormatException();
}
const points = [new ResultPoint(startRange[1], rowNumber), new ResultPoint(endRange[0], rowNumber)];
let resultReturn = new Result(resultString, null, // no natural byte representation for these barcodes
0, points, BarcodeFormat.ITF, new Date().getTime());
return resultReturn;
}
/*
/!**
* @param row row of black/white values to search
* @param payloadStart offset of start pattern
* @param resultString {@link StringBuilder} to append decoded chars to
* @throws NotFoundException if decoding could not complete successfully
*!/*/
static decodeMiddle(row, payloadStart, payloadEnd, resultString) {
// Digits are interleaved in pairs - 5 black lines for one digit, and the
// 5
// interleaved white lines for the second digit.
// Therefore, need to scan 10 lines and then
// split these into two arrays
let counterDigitPair = new Int32Array(10); // 10
let counterBlack = new Int32Array(5); // 5
let counterWhite = new Int32Array(5); // 5
counterDigitPair.fill(0);
counterBlack.fill(0);
counterWhite.fill(0);
while (payloadStart < payloadEnd) {
// Get 10 runs of black/white.
OneDReader.recordPattern(row, payloadStart, counterDigitPair);
// Split them into each array
for (let k = 0; k < 5; k++) {
let twoK = 2 * k;
counterBlack[k] = counterDigitPair[twoK];
counterWhite[k] = counterDigitPair[twoK + 1];
}
let bestMatch = ITFReader.decodeDigit(counterBlack);
resultString.append(bestMatch.toString());
bestMatch = this.decodeDigit(counterWhite);
resultString.append(bestMatch.toString());
counterDigitPair.forEach(function (counterDigit) {
payloadStart += counterDigit;
});
}
}
/*/!**
* Identify where the start of the middle / payload section starts.
*
* @param row row of black/white values to search
* @return Array, containing index of start of 'start block' and end of
* 'start block'
*!/*/
decodeStart(row) {
let endStart = ITFReader.skipWhiteSpace(row);
let startPattern = ITFReader.findGuardPattern(row, endStart, ITFReader.START_PATTERN);
// Determine the width of a narrow line in pixels. We can do this by
// getting the width of the start pattern and dividing by 4 because its
// made up of 4 narrow lines.
this.narrowLineWidth = (startPattern[1] - startPattern[0]) / 4;
this.validateQuietZone(row, startPattern[0]);
return startPattern;
}
/*/!**
* The start & end patterns must be pre/post fixed by a quiet zone. This
* zone must be at least 10 times the width of a narrow line. Scan back until
* we either get to the start of the barcode or match the necessary number of
* quiet zone pixels.
*
* Note: Its assumed the row is reversed when using this method to find
* quiet zone after the end pattern.
*
* ref: http://www.barcode-1.net/i25code.html
*
* @param row bit array representing the scanned barcode.
* @param startPattern index into row of the start or end pattern.
* @throws NotFoundException if the quiet zone cannot be found
*!/*/
validateQuietZone(row, startPattern) {
let quietCount = this.narrowLineWidth * 10; // expect to find this many pixels of quiet zone
// if there are not so many pixel at all let's try as many as possible
quietCount = quietCount < startPattern ? quietCount : startPattern;
for (let i = startPattern - 1; quietCount > 0 && i >= 0; i--) {
if (row.get(i)) {
break;
}
quietCount--;
}
if (quietCount !== 0) {
// Unable to find the necessary number of quiet zone pixels.
throw new NotFoundException();
}
}
/*
/!**
* Skip all whitespace until we get to the first black line.
*
* @param row row of black/white values to search
* @return index of the first black line.
* @throws NotFoundException Throws exception if no black lines are found in the row
*!/*/
static skipWhiteSpace(row) {
const width = row.getSize();
const endStart = row.getNextSet(0);
if (endStart === width) {
throw new NotFoundException();
}
return endStart;
}
/*/!**
* Identify where the end of the middle / payload section ends.
*
* @param row row of black/white values to search
* @return Array, containing index of start of 'end block' and end of 'end
* block'
*!/*/
decodeEnd(row) {
// For convenience, reverse the row and then
// search from 'the start' for the end block
row.reverse();
try {
let endStart = ITFReader.skipWhiteSpace(row);
let endPattern;
try {
endPattern = ITFReader.findGuardPattern(row, endStart, ITFReader.END_PATTERN_REVERSED[0]);
}
catch (error) {
if (error instanceof NotFoundException) {
endPattern = ITFReader.findGuardPattern(row, endStart, ITFReader.END_PATTERN_REVERSED[1]);
}
}
// The start & end patterns must be pre/post fixed by a quiet zone. This
// zone must be at least 10 times the width of a narrow line.
// ref: http://www.barcode-1.net/i25code.html
this.validateQuietZone(row, endPattern[0]);
// Now recalculate the indices of where the 'endblock' starts & stops to
// accommodate
// the reversed nature of the search
let temp = endPattern[0];
endPattern[0] = row.getSize() - endPattern[1];
endPattern[1] = row.getSize() - temp;
return endPattern;
}
finally {
// Put the row back the right way.
row.reverse();
}
}
/*
/!**
* @param row row of black/white values to search
* @param rowOffset position to start search
* @param pattern pattern of counts of number of black and white pixels that are
* being searched for as a pattern
* @return start/end horizontal offset of guard pattern, as an array of two
* ints
* @throws NotFoundException if pattern is not found
*!/*/
static findGuardPattern(row, rowOffset, pattern) {
let patternLength = pattern.length;
let counters = new Int32Array(patternLength);
let width = row.getSize();
let isWhite = false;
let counterPosition = 0;
let patternStart = rowOffset;
counters.fill(0);
for (let x = rowOffset; x < width; x++) {
if (row.get(x) !== isWhite) {
counters[counterPosition]++;
}
else {
if (counterPosition === patternLength - 1) {
if (OneDReader.patternMatchVariance(counters, pattern, ITFReader.MAX_INDIVIDUAL_VARIANCE) < ITFReader.MAX_AVG_VARIANCE) {
return [patternStart, x];
}
patternStart += counters[0] + counters[1];
System.arraycopy(counters, 2, counters, 0, counterPosition - 1);
counters[counterPosition - 1] = 0;
counters[counterPosition] = 0;
counterPosition--;
}
else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw new NotFoundException();
}
/*/!**
* Attempts to decode a sequence of ITF black/white lines into single
* digit.
*
* @param counters the counts of runs of observed black/white/black/... values
* @return The decoded digit
* @throws NotFoundException if digit cannot be decoded
*!/*/
static decodeDigit(counters) {
let bestVariance = ITFReader.MAX_AVG_VARIANCE; // worst variance we'll accept
let bestMatch = -1;
let max = ITFReader.PATTERNS.length;
for (let i = 0; i < max; i++) {
let pattern = ITFReader.PATTERNS[i];
let variance = OneDReader.patternMatchVariance(counters, pattern, ITFReader.MAX_INDIVIDUAL_VARIANCE);
if (variance < bestVariance) {
bestVariance = variance;
bestMatch = i;
}
else if (variance === bestVariance) {
// if we find a second 'best match' with the same variance, we can not reliably report to have a suitable match
bestMatch = -1;
}
}
if (bestMatch >= 0) {
return bestMatch % 10;
}
else {
throw new NotFoundException();
}
}
}
ITFReader.PATTERNS = [
Int32Array.from([1, 1, 2, 2, 1]),
Int32Array.from([2, 1, 1, 1, 2]),
Int32Array.from([1, 2, 1, 1, 2]),
Int32Array.from([2, 2, 1, 1, 1]),
Int32Array.from([1, 1, 2, 1, 2]),
Int32Array.from([2, 1, 2, 1, 1]),
Int32Array.from([1, 2, 2, 1, 1]),
Int32Array.from([1, 1, 1, 2, 2]),
Int32Array.from([2, 1, 1, 2, 1]),
Int32Array.from([1, 2, 1, 2, 1]),
Int32Array.from([1, 1, 3, 3, 1]),
Int32Array.from([3, 1, 1, 1, 3]),
Int32Array.from([1, 3, 1, 1, 3]),
Int32Array.from([3, 3, 1, 1, 1]),
Int32Array.from([1, 1, 3, 1, 3]),
Int32Array.from([3, 1, 3, 1, 1]),
Int32Array.from([1, 3, 3, 1, 1]),
Int32Array.from([1, 1, 1, 3, 3]),
Int32Array.from([3, 1, 1, 3, 1]),
Int32Array.from([1, 3, 1, 3, 1]) // 9
];
ITFReader.MAX_AVG_VARIANCE = 0.38;
ITFReader.MAX_INDIVIDUAL_VARIANCE = 0.5;
/* /!** Valid ITF lengths. Anything longer than the largest value is also allowed. *!/*/
ITFReader.DEFAULT_ALLOWED_LENGTHS = [6, 8, 10, 12, 14];
/*/!**
* Start/end guard pattern.
*
* Note: The end pattern is reversed because the row is reversed before
* searching for the END_PATTERN
*!/*/
ITFReader.START_PATTERN = Int32Array.from([1, 1, 1, 1]);
ITFReader.END_PATTERN_REVERSED = [
Int32Array.from([1, 1, 2]),
Int32Array.from([1, 1, 3]) // 3x
];