2 * Copyright 2007 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.qrcode;
19 import com.google.zxing.BarcodeFormat;
20 import com.google.zxing.DecodeHintType;
21 import com.google.zxing.MonochromeBitmapSource;
22 import com.google.zxing.Reader;
23 import com.google.zxing.ReaderException;
24 import com.google.zxing.Result;
25 import com.google.zxing.ResultPoint;
26 import com.google.zxing.common.BitMatrix;
27 import com.google.zxing.qrcode.decoder.Decoder;
28 import com.google.zxing.qrcode.detector.Detector;
29 import com.google.zxing.qrcode.detector.DetectorResult;
31 import java.util.Hashtable;
34 * This implementation can detect and decode QR Codes in an image.
36 * @author srowen@google.com (Sean Owen)
38 public final class QRCodeReader implements Reader {
40 private static final ResultPoint[] NO_POINTS = new ResultPoint[0];
42 private final Decoder decoder = new Decoder();
45 * Locates and decodes a QR code in an image.
47 * @return a String representing the content encoded by the QR code
48 * @throws ReaderException if a QR code cannot be found, or cannot be decoded
50 public Result decode(MonochromeBitmapSource image) throws ReaderException {
51 return decode(image, null);
54 public Result decode(MonochromeBitmapSource image, Hashtable hints)
55 throws ReaderException {
58 if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
59 BitMatrix bits = extractPureBits(image);
60 text = decoder.decode(bits);
63 DetectorResult result = new Detector(image).detect();
64 text = decoder.decode(result.getBits());
65 points = result.getPoints();
67 return new Result(text, points, BarcodeFormat.QR_CODE);
71 * This method detects a barcode in a "pure" image -- that is, pure monochrome image
72 * which contains only an unrotated, unskewed, image of a barcode, with some white border
73 * around it. This is a specialized method that works exceptionally fast in this special
76 private static BitMatrix extractPureBits(MonochromeBitmapSource image)
77 throws ReaderException {
78 // Now need to determine module size in pixels
80 // First, skip white border by tracking diagonally from the top left down and to the right:
82 while (!image.isBlack(borderWidth, borderWidth)) {
85 // And then keep tracking across the top-left black module to determine module size
86 int moduleEnd = borderWidth;
87 while (image.isBlack(moduleEnd, moduleEnd)) {
90 int moduleSize = moduleEnd - borderWidth;
92 // And now find where the rightmost black module on the first row ends
93 int rowEndOfSymbol = image.getWidth() - 1;
94 while (!image.isBlack(rowEndOfSymbol, borderWidth)) {
99 // Make sure width of barcode is a multiple of module size
100 if ((rowEndOfSymbol - borderWidth) % moduleSize != 0) {
101 throw new ReaderException("Bad module size / width: " + moduleSize +
102 " / " + (rowEndOfSymbol - borderWidth));
104 int dimension = (rowEndOfSymbol - borderWidth) / moduleSize;
106 // Push in the "border" by half the module width so that we start
107 // sampling in the middle of the module. Just in case the image is a
108 // little off, this will help recover.
109 borderWidth += moduleSize >> 1;
111 // Now just read off the bits
112 BitMatrix bits = new BitMatrix(dimension);
113 for (int i = 0; i < dimension; i++) {
114 int iOffset = borderWidth + i * moduleSize;
115 for (int j = 0; j < dimension; j++) {
116 if (image.isBlack(borderWidth + j * moduleSize, iOffset)) {