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Core barcode encoding/decoding library
/*
* 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.
*/
package com.google.zxing.oned;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.ChecksumException;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
import com.google.zxing.ResultMetadataType;
import com.google.zxing.ResultPoint;
import com.google.zxing.ResultPointCallback;
import com.google.zxing.common.BitArray;
import java.util.Arrays;
import java.util.Map;
/**
* Encapsulates functionality and implementation that is common to UPC and EAN families
* of one-dimensional barcodes.
*
* @author [email protected] (Daniel Switkin)
* @author Sean Owen
* @author [email protected] (Alasdair Mackintosh)
*/
public abstract class UPCEANReader extends OneDReader {
// 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.
private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.48f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
/**
* Start/end guard pattern.
*/
static final int[] START_END_PATTERN = {1, 1, 1,};
/**
* Pattern marking the middle of a UPC/EAN pattern, separating the two halves.
*/
static final int[] MIDDLE_PATTERN = {1, 1, 1, 1, 1};
/**
* "Odd", or "L" patterns used to encode UPC/EAN digits.
*/
static final int[][] L_PATTERNS = {
{3, 2, 1, 1}, // 0
{2, 2, 2, 1}, // 1
{2, 1, 2, 2}, // 2
{1, 4, 1, 1}, // 3
{1, 1, 3, 2}, // 4
{1, 2, 3, 1}, // 5
{1, 1, 1, 4}, // 6
{1, 3, 1, 2}, // 7
{1, 2, 1, 3}, // 8
{3, 1, 1, 2} // 9
};
/**
* As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.
*/
static final int[][] L_AND_G_PATTERNS;
static {
L_AND_G_PATTERNS = new int[20][];
System.arraycopy(L_PATTERNS, 0, L_AND_G_PATTERNS, 0, 10);
for (int i = 10; i < 20; i++) {
int[] widths = L_PATTERNS[i - 10];
int[] reversedWidths = new int[widths.length];
for (int j = 0; j < widths.length; j++) {
reversedWidths[j] = widths[widths.length - j - 1];
}
L_AND_G_PATTERNS[i] = reversedWidths;
}
}
private final StringBuilder decodeRowStringBuffer;
private final UPCEANExtensionSupport extensionReader;
private final EANManufacturerOrgSupport eanManSupport;
protected UPCEANReader() {
decodeRowStringBuffer = new StringBuilder(20);
extensionReader = new UPCEANExtensionSupport();
eanManSupport = new EANManufacturerOrgSupport();
}
static int[] findStartGuardPattern(BitArray row) throws NotFoundException {
boolean foundStart = false;
int[] startRange = null;
int nextStart = 0;
int[] counters = new int[START_END_PATTERN.length];
while (!foundStart) {
Arrays.fill(counters, 0, START_END_PATTERN.length, 0);
startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN, counters);
int start = startRange[0];
nextStart = startRange[1];
// Make sure there is a quiet zone at least as big as the start pattern before the barcode.
// If this check would run off the left edge of the image, do not accept this barcode,
// as it is very likely to be a false positive.
int quietStart = start - (nextStart - start);
if (quietStart >= 0) {
foundStart = row.isRange(quietStart, start, false);
}
}
return startRange;
}
@Override
public Result decodeRow(int rowNumber, BitArray row, Map hints)
throws NotFoundException, ChecksumException, FormatException {
return decodeRow(rowNumber, row, findStartGuardPattern(row), hints);
}
/**
* Like {@link #decodeRow(int, BitArray, java.util.Map)}, but
* allows caller to inform method about where the UPC/EAN start pattern is
* found. This allows this to be computed once and reused across many implementations.
*/
public Result decodeRow(int rowNumber,
BitArray row,
int[] startGuardRange,
Map hints)
throws NotFoundException, ChecksumException, FormatException {
ResultPointCallback resultPointCallback = hints == null ? null :
(ResultPointCallback) hints.get(DecodeHintType.NEED_RESULT_POINT_CALLBACK);
if (resultPointCallback != null) {
resultPointCallback.foundPossibleResultPoint(new ResultPoint(
(startGuardRange[0] + startGuardRange[1]) / 2.0f, rowNumber
));
}
StringBuilder result = decodeRowStringBuffer;
result.setLength(0);
int endStart = decodeMiddle(row, startGuardRange, result);
if (resultPointCallback != null) {
resultPointCallback.foundPossibleResultPoint(new ResultPoint(
endStart, rowNumber
));
}
int[] endRange = decodeEnd(row, endStart);
if (resultPointCallback != null) {
resultPointCallback.foundPossibleResultPoint(new ResultPoint(
(endRange[0] + endRange[1]) / 2.0f, rowNumber
));
}
// Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
// spec might want more whitespace, but in practice this is the maximum we can count on.
int end = endRange[1];
int quietEnd = end + (end - endRange[0]);
if (quietEnd >= row.getSize() || !row.isRange(end, quietEnd, false)) {
throw NotFoundException.getNotFoundInstance();
}
String resultString = result.toString();
if (!checkChecksum(resultString)) {
throw ChecksumException.getChecksumInstance();
}
float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
float right = (float) (endRange[1] + endRange[0]) / 2.0f;
BarcodeFormat format = getBarcodeFormat();
Result decodeResult = new Result(resultString,
null, // no natural byte representation for these barcodes
new ResultPoint[]{
new ResultPoint(left, (float) rowNumber),
new ResultPoint(right, (float) rowNumber)},
format);
try {
Result extensionResult = extensionReader.decodeRow(rowNumber, row, endRange[1]);
decodeResult.putAllMetadata(extensionResult.getResultMetadata());
decodeResult.addResultPoints(extensionResult.getResultPoints());
} catch (ReaderException re) {
// continue
}
if (format == BarcodeFormat.EAN_13 || format == BarcodeFormat.UPC_A) {
String countryID = eanManSupport.lookupCountryIdentifier(resultString);
if (countryID != null) {
decodeResult.putMetadata(ResultMetadataType.POSSIBLE_COUNTRY, countryID);
}
}
return decodeResult;
}
/**
* @return {@link #checkStandardUPCEANChecksum(CharSequence)}
*/
boolean checkChecksum(String s) throws ChecksumException, FormatException {
return checkStandardUPCEANChecksum(s);
}
/**
* Computes the UPC/EAN checksum on a string of digits, and reports
* whether the checksum is correct or not.
*
* @param s string of digits to check
* @return true iff string of digits passes the UPC/EAN checksum algorithm
* @throws FormatException if the string does not contain only digits
*/
private static boolean checkStandardUPCEANChecksum(CharSequence s) throws FormatException {
int length = s.length();
if (length == 0) {
return false;
}
int sum = 0;
for (int i = length - 2; i >= 0; i -= 2) {
int digit = (int) s.charAt(i) - (int) '0';
if (digit < 0 || digit > 9) {
throw FormatException.getFormatInstance();
}
sum += digit;
}
sum *= 3;
for (int i = length - 1; i >= 0; i -= 2) {
int digit = (int) s.charAt(i) - (int) '0';
if (digit < 0 || digit > 9) {
throw FormatException.getFormatInstance();
}
sum += digit;
}
return sum % 10 == 0;
}
int[] decodeEnd(BitArray row, int endStart) throws NotFoundException {
return findGuardPattern(row, endStart, false, START_END_PATTERN);
}
static int[] findGuardPattern(BitArray row,
int rowOffset,
boolean whiteFirst,
int[] pattern) throws NotFoundException {
return findGuardPattern(row, rowOffset, whiteFirst, pattern, new int[pattern.length]);
}
/**
* @param row row of black/white values to search
* @param rowOffset position to start search
* @param whiteFirst if true, indicates that the pattern specifies white/black/white/...
* pixel counts, otherwise, it is interpreted as black/white/black/...
* @param pattern pattern of counts of number of black and white pixels that are being
* searched for as a pattern
* @param counters array of counters, as long as pattern, to re-use
* @return start/end horizontal offset of guard pattern, as an array of two ints
* @throws NotFoundException if pattern is not found
*/
static int[] findGuardPattern(BitArray row,
int rowOffset,
boolean whiteFirst,
int[] pattern,
int[] counters) throws NotFoundException {
int patternLength = pattern.length;
int width = row.getSize();
boolean isWhite = whiteFirst;
rowOffset = whiteFirst ? row.getNextUnset(rowOffset) : row.getNextSet(rowOffset);
int counterPosition = 0;
int patternStart = rowOffset;
for (int x = rowOffset; x < width; x++) {
if (row.get(x) ^ isWhite) {
counters[counterPosition]++;
} else {
if (counterPosition == patternLength - 1) {
if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
return new int[]{patternStart, x};
}
patternStart += counters[0] + counters[1];
System.arraycopy(counters, 2, counters, 0, patternLength - 2);
counters[patternLength - 2] = 0;
counters[patternLength - 1] = 0;
counterPosition--;
} else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw NotFoundException.getNotFoundInstance();
}
/**
* Attempts to decode a single UPC/EAN-encoded digit.
*
* @param row row of black/white values to decode
* @param counters the counts of runs of observed black/white/black/... values
* @param rowOffset horizontal offset to start decoding from
* @param patterns the set of patterns to use to decode -- sometimes different encodings
* for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
* be used
* @return horizontal offset of first pixel beyond the decoded digit
* @throws NotFoundException if digit cannot be decoded
*/
static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
throws NotFoundException {
recordPattern(row, rowOffset, counters);
int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
int bestMatch = -1;
int max = patterns.length;
for (int i = 0; i < max; i++) {
int[] pattern = patterns[i];
int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
if (variance < bestVariance) {
bestVariance = variance;
bestMatch = i;
}
}
if (bestMatch >= 0) {
return bestMatch;
} else {
throw NotFoundException.getNotFoundInstance();
}
}
/**
* Get the format of this decoder.
*
* @return The 1D format.
*/
abstract BarcodeFormat getBarcodeFormat();
/**
* Subclasses override this to decode the portion of a barcode between the start
* and end guard patterns.
*
* @param row row of black/white values to search
* @param startRange start/end offset of start guard pattern
* @param resultString {@link StringBuilder} to append decoded chars to
* @return horizontal offset of first pixel after the "middle" that was decoded
* @throws NotFoundException if decoding could not complete successfully
*/
protected abstract int decodeMiddle(BitArray row,
int[] startRange,
StringBuilder resultString) throws NotFoundException;
}
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