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VulnAbstractOneDReader.java
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VulnAbstractOneDReader.java
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/*
* 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.BlackPointEstimationMethod;
import com.google.zxing.DecodeHintType;
import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
import com.google.zxing.ResultMetadataType;
import com.google.zxing.common.BitArray;
import java.util.Hashtable;
/**
* <p>Encapsulates functionality and implementation that is common to all families
* of one-dimensional barcodes.</p>
*
* @author [email protected] (Daniel Switkin)
* @author [email protected] (Sean Owen)
*/
public abstract class AbstractOneDReader implements OneDReader {
private static final int INTEGER_MATH_SHIFT = 8;
static final int PATTERN_MATCH_RESULT_SCALE_FACTOR = 1 << INTEGER_MATH_SHIFT;
public final Result decode(MonochromeBitmapSource image) throws ReaderException {
return decode(image, null);
}
public final Result decode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
try {
return doDecode(image, hints);
} catch (ReaderException re) {
boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
if (tryHarder && image.isRotateSupported()) {
MonochromeBitmapSource rotatedImage = image.rotateCounterClockwise();
Result result = doDecode(rotatedImage, hints);
// Record that we found it rotated 90 degrees CCW / 270 degrees CW
Hashtable metadata = result.getResultMetadata();
int orientation = 270;
if (metadata != null && metadata.containsKey(ResultMetadataType.ORIENTATION)) {
// But if we found it reversed in doDecode(), add in that result here:
orientation = (orientation + ((Integer) metadata.get(ResultMetadataType.ORIENTATION)).intValue()) % 360;
}
result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(orientation));
return result;
} else {
throw re;
}
}
}
/**
* We're going to examine rows from the middle outward, searching alternately above and below the
* middle, and farther out each time. rowStep is the number of rows between each successive
* attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
* middle + rowStep, then middle - (2 * rowStep), etc.
* rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
* decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
* image if "trying harder".
*
* @param image The image to decode
* @param hints Any hints that were requested
* @return The contents of the decoded barcode
* @throws ReaderException Any spontaneous errors which occur
*/
private Result doDecode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
int width = image.getWidth();
int height = image.getHeight();
BitArray row = new BitArray(width);
int middle = height >> 1;
boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
int rowStep = Math.max(1, height >> (tryHarder ? 7 : 4));
int maxLines;
if (tryHarder) {
maxLines = height; // Look at the whole image, not just the center
} else {
maxLines = 9; // Nine rows spaced 1/16 apart is roughly the middle half of the image
}
for (int x = 0; x < maxLines; x++) {
// Scanning from the middle out. Determine which row we're looking at next:
int rowStepsAboveOrBelow = (x + 1) >> 1;
boolean isAbove = (x & 0x01) == 0; // i.e. is x even?
int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
if (rowNumber < 0 || rowNumber >= height) {
// Oops, if we run off the top or bottom, stop
break;
}
// Estimate black point for this row and load it:
try {
image.estimateBlackPoint(BlackPointEstimationMethod.ROW_SAMPLING, rowNumber);
} catch (ReaderException re) {
continue;
}
image.getBlackRow(rowNumber, row, 0, width);
// While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
// handle decoding upside down barcodes.
for (int attempt = 0; attempt < 2; attempt++) {
if (attempt == 1) { // trying again?
row.reverse(); // reverse the row and continue
}
try {
// Look for a barcode
Result result = decodeRow(rowNumber, row, hints);
// We found our barcode
if (attempt == 1) {
// But it was upside down, so note that
result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(180));
}
return result;
} catch (ReaderException re) {
// continue -- just couldn't decode this row
}
}
}
throw new ReaderException("No barcode found");
}
/**
* Records the size of successive runs of white and black pixels in a row, starting at a given point.
* The values are recorded in the given array, and the number of runs recorded is equal to the size
* of the array. If the row starts on a white pixel at the given start point, then the first count
* recorded is the run of white pixels starting from that point; likewise it is the count of a run
* of black pixels if the row begin on a black pixels at that point.
*
* @param row row to count from
* @param start offset into row to start at
* @param counters array into which to record counts
* @throws ReaderException if counters cannot be filled entirely from row before running out of pixels
*/
static void recordPattern(BitArray row, int start, int[] counters) throws ReaderException {
int numCounters = counters.length;
for (int i = 0; i < numCounters; i++) {
counters[i] = 0;
}
int end = row.getSize();
if (start >= end) {
throw new ReaderException("Couldn't fully read a pattern");
}
boolean isWhite = !row.get(start);
int counterPosition = 0;
int i = start;
while (i < end) {
boolean pixel = row.get(i);
if ((!pixel && isWhite) || (pixel && !isWhite)) {
counters[counterPosition]++;
} else {
counterPosition++;
if (counterPosition == numCounters) {
break;
} else {
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
i++;
}
// If we read fully the last section of pixels and filled up our counters -- or filled
// the last counter but ran off the side of the image, OK. Otherwise, a problem.
if (!(counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end))) {
throw new ReaderException("Couldn't fully read a pattern");
}
}
/**
* Determines how closely a set of observed counts of runs of black/white values matches a given
* target pattern. This is reported as the ratio of the total variance from the expected pattern
* proportions across all pattern elements, to the length of the pattern.
*
* @param counters observed counters
* @param pattern expected pattern
* @param maxIndividualVariance The most any counter can differ before we give up
* @return ratio of total variance between counters and pattern compared to total pattern size,
* where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means
* the total variance between counters and patterns equals the pattern length, higher values mean
* even more variance
*/
static int patternMatchVariance(int[] counters, int[] pattern, int maxIndividualVariance) {
int numCounters = counters.length;
int total = 0;
int patternLength = 0;
for (int i = 0; i < numCounters; i++) {
total += counters[i];
patternLength += pattern[i];
}
if (total < patternLength) {
// If we don't even have one pixel per unit of bar width, assume this is too small
// to reliably match, so fail:
return Integer.MAX_VALUE;
}
// We're going to fake floating-point math in integers. We just need to use more bits.
// Scale up patternLength so that intermediate values below like scaledCounter will have
// more "significant digits"
int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;
int totalVariance = 0;
for (int x = 0; x < numCounters; x++) {
int counter = counters[x] << INTEGER_MATH_SHIFT;
int scaledPattern = pattern[x] * unitBarWidth;
int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
if (variance > maxIndividualVariance) {
return Integer.MAX_VALUE;
}
totalVariance += variance;
}
return totalVariance / total;
}
// This declaration should not be necessary, since this class is
// abstract and so does not have to provide an implementation for every
// method of an interface it implements, but it is causing NoSuchMethodError
// issues on some Nokia JVMs. So we add this superfluous declaration:
public abstract Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException;
}