2 * Copyright 2008 Google Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 package com.google.zxing.oned;
19 import com.google.zxing.BlackPointEstimationMethod;
20 import com.google.zxing.MonochromeBitmapSource;
21 import com.google.zxing.ReaderException;
22 import com.google.zxing.Result;
23 import com.google.zxing.common.BitArray;
25 import java.util.Hashtable;
28 * <p>Encapsulates functionality and implementation that is common to all families
29 * of one-dimensional barcodes.</p>
31 * @author dswitkin@google.com (Daniel Switkin)
32 * @author srowen@google.com (Sean Owen)
34 public abstract class AbstractOneDReader implements OneDReader {
36 public final Result decode(MonochromeBitmapSource image) throws ReaderException {
37 return decode(image, null);
40 public final Result decode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
42 int width = image.getWidth();
43 int height = image.getHeight();
45 BitArray row = new BitArray(width);
47 // We're going to examine rows from the middle outward, searching alternately above and below the middle,
48 // and farther out each time. rowStep is the number of rows between each successive attempt above and below
49 // the middle. So we'd scan row middle, then middle - rowStep, then middle + rowStep,
50 // then middle - 2*rowStep, etc.
51 // rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily decided
52 // that moving up and down by about 1/16 of the image is pretty good.
53 int middle = height >> 1;
54 int rowStep = Math.max(1, height >> 5);
55 for (int x = 0; x < 11; x++) {
57 int rowStepsAboveOrBelow = (x + 1) >> 1;
58 boolean isAbove = (x & 0x01) == 0; // i.e. is x even?
59 int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
61 image.estimateBlackPoint(BlackPointEstimationMethod.ROW_SAMPLING, rowNumber);
62 image.getBlackRow(rowNumber, row, 0, width);
65 return decodeRow(rowNumber, row);
66 } catch (ReaderException re) {
67 // TODO re-enable this in a "try harder" mode?
68 //row.reverse(); // try scanning the row backwards
70 // return decodeRow(rowNumber, row);
71 //} catch (ReaderException re2) {
78 throw new ReaderException("No barcode found");
81 protected static void recordPattern(BitArray row, int start, int[] counters) throws ReaderException {
82 for (int i = 0; i < counters.length; i++) {
85 int end = row.getSize();
87 throw new ReaderException("Couldn't fully read a pattern");
89 boolean isWhite = !row.get(start);
90 int counterPosition = 0;
93 boolean pixel = row.get(i);
94 if ((!pixel && isWhite) || (pixel && !isWhite)) {
95 counters[counterPosition]++;
98 if (counterPosition == counters.length) {
101 counters[counterPosition] = 1;
107 // If we read fully the last section of pixels and filled up our counters -- or filled
108 // the last counter but ran off the side of the image, OK. Otherwise, a problem.
109 if (!(counterPosition == counters.length || (counterPosition == counters.length - 1 && i == end))) {
110 throw new ReaderException("Couldn't fully read a pattern");
115 * Determines how closely a set of observed counts of runs of black/white values matches a given
116 * target pattern. For each counter, the ratio of the difference between it and the pattern value
117 * is compared to the expected pattern value. This ratio is averaged across counters to produce
118 * the return value. 0.0 means an exact match; higher values mean poorer matches.
120 * @param counters observed counters
121 * @param pattern expected pattern
122 * @return average variance between counters and pattern
124 protected static float patternMatchVariance(int[] counters, int[] pattern) {
126 int numCounters = counters.length;
127 int patternLength = 0;
128 for (int i = 0; i < numCounters; i++) {
129 total += counters[i];
130 patternLength += pattern[i];
132 float unitBarWidth = (float) total / (float) patternLength;
134 float totalVariance = 0.0f;
135 for (int x = 0; x < numCounters; x++) {
136 float scaledCounter = (float) counters[x] / unitBarWidth;
137 float width = pattern[x];
138 float abs = scaledCounter > width ? scaledCounter - width : width - scaledCounter;
139 totalVariance += abs / width;
141 return totalVariance / (float) numCounters;
147 * @return argument rounded to nearest int
149 protected static int round(float f) {
150 return (int) (f + 0.5f);