com.google.zxing.oned.OneDReader Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
Show all versions of core Show documentation
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.BinaryBitmap;
import com.google.zxing.ChecksumException;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Reader;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
import com.google.zxing.ResultMetadataType;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitArray;
import java.util.Arrays;
import java.util.EnumMap;
import java.util.Map;
/**
* Encapsulates functionality and implementation that is common to all families
* of one-dimensional barcodes.
*
* @author [email protected] (Daniel Switkin)
* @author Sean Owen
*/
public abstract class OneDReader implements Reader {
@Override
public Result decode(BinaryBitmap image) throws NotFoundException, FormatException {
return decode(image, null);
}
// Note that we don't try rotation without the try harder flag, even if rotation was supported.
@Override
public Result decode(BinaryBitmap image,
Map hints) throws NotFoundException, FormatException {
try {
return doDecode(image, hints);
} catch (NotFoundException nfe) {
boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
if (tryHarder && image.isRotateSupported()) {
BinaryBitmap rotatedImage = image.rotateCounterClockwise();
Result result = doDecode(rotatedImage, hints);
// Record that we found it rotated 90 degrees CCW / 270 degrees CW
Map 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)) % 360;
}
result.putMetadata(ResultMetadataType.ORIENTATION, orientation);
// Update result points
ResultPoint[] points = result.getResultPoints();
if (points != null) {
int height = rotatedImage.getHeight();
for (int i = 0; i < points.length; i++) {
points[i] = new ResultPoint(height - points[i].getY() - 1, points[i].getX());
}
}
return result;
} else {
throw nfe;
}
}
}
@Override
public void reset() {
// do nothing
}
/**
* 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 NotFoundException Any spontaneous errors which occur
*/
private Result doDecode(BinaryBitmap image,
Map hints) throws NotFoundException {
int width = image.getWidth();
int height = image.getHeight();
BitArray row = new BitArray(width);
boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
int rowStep = Math.max(1, height >> (tryHarder ? 8 : 5));
int maxLines;
if (tryHarder) {
maxLines = height; // Look at the whole image, not just the center
} else {
maxLines = 15; // 15 rows spaced 1/32 apart is roughly the middle half of the image
}
int middle = height / 2;
for (int x = 0; x < maxLines; x++) {
// Scanning from the middle out. Determine which row we're looking at next:
int rowStepsAboveOrBelow = (x + 1) / 2;
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 {
row = image.getBlackRow(rowNumber, row);
} catch (NotFoundException ignored) {
continue;
}
// 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
// This means we will only ever draw result points *once* in the life of this method
// since we want to avoid drawing the wrong points after flipping the row, and,
// don't want to clutter with noise from every single row scan -- just the scans
// that start on the center line.
if (hints != null && hints.containsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK)) {
Map newHints = new EnumMap<>(DecodeHintType.class);
newHints.putAll(hints);
newHints.remove(DecodeHintType.NEED_RESULT_POINT_CALLBACK);
hints = newHints;
}
}
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, 180);
// And remember to flip the result points horizontally.
ResultPoint[] points = result.getResultPoints();
if (points != null) {
points[0] = new ResultPoint(width - points[0].getX() - 1, points[0].getY());
points[1] = new ResultPoint(width - points[1].getX() - 1, points[1].getY());
}
}
return result;
} catch (ReaderException re) {
// continue -- just couldn't decode this row
}
}
}
throw NotFoundException.getNotFoundInstance();
}
/**
* 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 NotFoundException if counters cannot be filled entirely from row before running out
* of pixels
*/
protected static void recordPattern(BitArray row,
int start,
int[] counters) throws NotFoundException {
int numCounters = counters.length;
Arrays.fill(counters, 0, numCounters, 0);
int end = row.getSize();
if (start >= end) {
throw NotFoundException.getNotFoundInstance();
}
boolean isWhite = !row.get(start);
int counterPosition = 0;
int i = start;
while (i < end) {
if (row.get(i) != isWhite) {
counters[counterPosition]++;
} else {
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 NotFoundException.getNotFoundInstance();
}
}
protected static void recordPatternInReverse(BitArray row, int start, int[] counters)
throws NotFoundException {
// This could be more efficient I guess
int numTransitionsLeft = counters.length;
boolean last = row.get(start);
while (start > 0 && numTransitionsLeft >= 0) {
if (row.get(--start) != last) {
numTransitionsLeft--;
last = !last;
}
}
if (numTransitionsLeft >= 0) {
throw NotFoundException.getNotFoundInstance();
}
recordPattern(row, start + 1, counters);
}
/**
* 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
*/
protected static float patternMatchVariance(int[] counters,
int[] pattern,
float 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 Float.POSITIVE_INFINITY;
}
float unitBarWidth = (float) total / patternLength;
maxIndividualVariance *= unitBarWidth;
float totalVariance = 0.0f;
for (int x = 0; x < numCounters; x++) {
int counter = counters[x];
float scaledPattern = pattern[x] * unitBarWidth;
float variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
if (variance > maxIndividualVariance) {
return Float.POSITIVE_INFINITY;
}
totalVariance += variance;
}
return totalVariance / total;
}
/**
* Attempts to decode a one-dimensional barcode format given a single row of
* an image.
*
* @param rowNumber row number from top of the row
* @param row the black/white pixel data of the row
* @param hints decode hints
* @return {@link Result} containing encoded string and start/end of barcode
* @throws NotFoundException if no potential barcode is found
* @throws ChecksumException if a potential barcode is found but does not pass its checksum
* @throws FormatException if a potential barcode is found but format is invalid
*/
public abstract Result decodeRow(int rowNumber, BitArray row, Map hints)
throws NotFoundException, ChecksumException, FormatException;
}