/*
* 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 dswitkin@google.com (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<DecodeHintType, ?> 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<ResultMetadataType, ?> 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<DecodeHintType, ?> hints)
throws NotFoundException {
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 ? 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
}
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<DecodeHintType, Object> 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) { // that is, exactly one is true
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 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;
}
/**
* <p>
* Attempts to decode a one-dimensional barcode format given a single row of
* an image.
* </p>
*
* @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<DecodeHintType, ?> hints) throws NotFoundException,
ChecksumException, FormatException;
}