@tjieco/library
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TypeScript port of ZXing multi-format 1D/2D barcode image processing library, with Code128 and ITF support.
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text/typescript
/*
* 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 BitArray from '../common/BitArray';
import DecodeHintType from '../DecodeHintType';
import Exception from '../Exception';
import Result from '../Result';
import ResultPoint from '../ResultPoint';
import OneDReader from './OneDReader';
import StringBuilder from "../util/StringBuilder";
import System from "../util/System";
/**
* <p>Decodes ITF barcodes.</p>
*
* @author Tjieco
*/
export default class ITFReader extends OneDReader {
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
private static PATTERNS: number[][] = [
[1, 1, 2, 2, 1], // 0
[2, 1, 1, 1, 2], // 1
[1, 2, 1, 1, 2], // 2
[2, 2, 1, 1, 1], // 3
[1, 1, 2, 1, 2], // 4
[2, 1, 2, 1, 1], // 5
[1, 2, 2, 1, 1], // 6
[1, 1, 1, 2, 2], // 7
[2, 1, 1, 2, 1], // 8
[1, 2, 1, 2, 1], // 9
[1, 1, 3, 3, 1], // 0
[3, 1, 1, 1, 3], // 1
[1, 3, 1, 1, 3], // 2
[3, 3, 1, 1, 1], // 3
[1, 1, 3, 1, 3], // 4
[3, 1, 3, 1, 1], // 5
[1, 3, 3, 1, 1], // 6
[1, 1, 1, 3, 3], // 7
[3, 1, 1, 3, 1], // 8
[1, 3, 1, 3, 1] // 9
];
private static MAX_AVG_VARIANCE = 0.38;
private static MAX_INDIVIDUAL_VARIANCE = 0.5;
/* /!** Valid ITF lengths. Anything longer than the largest value is also allowed. *!/*/
private static DEFAULT_ALLOWED_LENGTHS:number[] = [6, 8, 10, 12, 14];
// Stores the actual narrow line width of the image being decoded.
private narrowLineWidth = -1;
/*/!**
* Start/end guard pattern.
*
* Note: The end pattern is reversed because the row is reversed before
* searching for the END_PATTERN
*!/*/
private static START_PATTERN = [1, 1, 1, 1];
private static END_PATTERN_REVERSED: number[][] = [
[1, 1, 2], // 2x
[1, 1, 3] // 3x
];
// See ITFWriter.PATTERNS
/*
/!**
* Patterns of Wide / Narrow lines to indicate each digit
*!/
*/
public decodeRow(rowNumber: number, row: BitArray, hints?: Map<DecodeHintType, any>): Result {
// Find out where the Middle section (payload) starts & ends
let startRange: number[] = this.decodeStart(row);
let endRange: number[] = this.decodeEnd(row);
let result: StringBuilder = new StringBuilder();
ITFReader.decodeMiddle(row, startRange[1], endRange[0], result);
let resultString: string = result.toString();
let allowedLengths: number[] = 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: number = resultString.length;
let lengthOK: boolean = false;
let maxAllowedLength: number = 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 Exception(Exception.FormatException)
}
const points: ResultPoint[] = [new ResultPoint(startRange[1], rowNumber), new ResultPoint(endRange[0], rowNumber)];
let resultReturn: Result = 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
*!/*/
private static decodeMiddle(row: BitArray,
payloadStart: number,
payloadEnd: number,
resultString: StringBuilder) {
// 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: number[] = new Array(10); //10
let counterBlack: number[]= new Array(5); //5
let counterWhite: number[]= new Array(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: number = 2 * k;
counterBlack[k] = counterDigitPair[twoK];
counterWhite[k] = counterDigitPair[twoK + 1];
}
let bestMatch: number = 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'
*!/*/
private decodeStart(row: BitArray): number[] {
let endStart = ITFReader.skipWhiteSpace(row);
let startPattern: number[] = 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
*!/*/
private validateQuietZone(row:BitArray, startPattern: number): void {
let quietCount: number = 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 Exception(Exception.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
*!/*/
private static skipWhiteSpace(row: BitArray): number {
let width: number = row.getSize();
let endStart: number = row.getNextSet(0);
if (endStart == width) {
throw new Exception(Exception.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'
*!/*/
private decodeEnd(row: BitArray): number[] {
// For convenience, reverse the row and then
// search from 'the start' for the end block
row.reverse();
try {
let endStart: number = ITFReader.skipWhiteSpace(row);
let endPattern: number[];
try {
endPattern = ITFReader.findGuardPattern(row, endStart, ITFReader.END_PATTERN_REVERSED[0]);
} catch (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
*!/*/
private static findGuardPattern(row: BitArray,
rowOffset: number,
pattern: number[]): number[] {
let patternLength: number = pattern.length;
let counters: number[] = new Array(patternLength);
let width: number = row.getSize();
let isWhite: boolean = false;
let counterPosition: number = 0;
let patternStart: number = 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 Exception (Exception.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
*!/*/
private static decodeDigit(counters: number[]): number {
let bestVariance: number = ITFReader.MAX_AVG_VARIANCE; // worst variance we'll accept
let bestMatch: number = -1;
let max: number = ITFReader.PATTERNS.length;
for (let i = 0; i < max; i++) {
let pattern = ITFReader.PATTERNS[i];
let variance: number = 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 Exception(Exception.NotFoundException)
}
}
}