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.client.j2se;
19 import com.google.zxing.BlackPointEstimationMethod;
20 import com.google.zxing.MonochromeBitmapSource;
21 import com.google.zxing.ReaderException;
22 import com.google.zxing.common.BitArray;
23 import com.google.zxing.common.BlackPointEstimator;
25 import java.awt.geom.AffineTransform;
26 import java.awt.image.AffineTransformOp;
27 import java.awt.image.BufferedImage;
28 import java.awt.image.BufferedImageOp;
31 * <p>An implementation based upon {@link BufferedImage}. This provides access to the
32 * underlying image as if it were a monochrome image. Behind the scenes, it is evaluating
33 * the luminance of the underlying image by retrieving its pixels' RGB values.</p>
35 * <p>This may also be used to construct a {@link MonochromeBitmapSource}
36 * based on a region of a {@link BufferedImage}; see
37 * {@link #BufferedImageMonochromeBitmapSource(BufferedImage, int, int, int, int)}.</p>
39 * @author srowen@google.com (Sean Owen), Daniel Switkin (dswitkin@google.com)
41 public final class BufferedImageMonochromeBitmapSource implements MonochromeBitmapSource {
43 private final BufferedImage image;
44 private final int left;
45 private final int top;
46 private final int width;
47 private final int height;
48 private int blackPoint;
49 private BlackPointEstimationMethod lastMethod;
50 private int lastArgument;
52 private static final int LUMINANCE_BITS = 5;
53 private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
54 private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
57 * Creates an instance that uses the entire given image as a source of pixels to decode.
59 * @param image image to decode
61 public BufferedImageMonochromeBitmapSource(BufferedImage image) {
62 this(image, 0, 0, image.getWidth(), image.getHeight());
66 * Creates an instance that uses only a region of the given image as a source of pixels to decode.
68 * @param image image to decode a region of
69 * @param left x coordinate of leftmost pixels to decode
70 * @param top y coordinate of topmost pixels to decode
71 * @param right one more than the x coordinate of rightmost pixels to decode. That is, we will decode
72 * pixels whose x coordinate is in [left,right)
73 * @param bottom likewise, one more than the y coordinate of the bottommost pixels to decode
75 public BufferedImageMonochromeBitmapSource(BufferedImage image, int left, int top, int right, int bottom) {
80 int sourceHeight = image.getHeight();
81 int sourceWidth = image.getWidth();
82 if (left < 0 || top < 0 || right > sourceWidth || bottom > sourceHeight || right <= left || bottom <= top) {
83 throw new IllegalArgumentException("Invalid bounds: (" + top + ',' + left + ") (" + right + ',' + bottom + ')');
87 this.width = right - left;
88 this.height = bottom - top;
92 * @return underlying {@link BufferedImage} behind this instance. Note that even if this instance
93 * only uses a subset of the full image, the returned value here represents the entire backing image.
95 public BufferedImage getImage() {
99 private int getRGB(int x, int y) {
100 return image.getRGB(left + x, top + y);
103 private void getRGBRow(int startX, int startY, int[] result) {
104 image.getRGB(left + startX, top + startY, result.length, 1, result, 0, result.length);
107 public boolean isBlack(int x, int y) {
108 return computeRGBLuminance(getRGB(x, y)) < blackPoint;
111 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
113 row = new BitArray(getWidth);
117 int[] pixelRow = new int[getWidth];
118 getRGBRow(startX, y, pixelRow);
119 for (int i = 0; i < getWidth; i++) {
120 if (computeRGBLuminance(pixelRow[i]) < blackPoint) {
127 public int getHeight() {
131 public int getWidth() {
135 public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException {
136 if (!method.equals(lastMethod) || argument != lastArgument) {
137 int[] histogram = new int[LUMINANCE_BUCKETS];
138 if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
139 int minDimension = width < height ? width : height;
140 int startI = height == minDimension ? 0 : (height - width) >> 1;
141 int startJ = width == minDimension ? 0 : (width - height) >> 1;
142 for (int n = 0; n < minDimension; n++) {
143 int pixel = getRGB(startJ + n, startI + n);
144 histogram[computeRGBLuminance(pixel) >> LUMINANCE_SHIFT]++;
146 } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
147 if (argument < 0 || argument >= height) {
148 throw new IllegalArgumentException("Row is not within the image: " + argument);
150 int[] rgbArray = new int[width];
151 getRGBRow(0, argument, rgbArray);
152 for (int x = 0; x < width; x++) {
153 histogram[computeRGBLuminance(rgbArray[x]) >> LUMINANCE_SHIFT]++;
156 throw new IllegalArgumentException("Unknown method: " + method);
158 blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
160 lastArgument = argument;
164 public BlackPointEstimationMethod getLastEstimationMethod() {
168 public MonochromeBitmapSource rotateCounterClockwise() {
169 if (!isRotateSupported()) {
170 throw new IllegalStateException("Rotate not supported");
172 int sourceWidth = image.getWidth();
173 int sourceHeight = image.getHeight();
174 // 90 degrees counterclockwise:
175 AffineTransform transform = new AffineTransform(0.0, -1.0, 1.0, 0.0, 0.0, sourceWidth);
176 BufferedImageOp op = new AffineTransformOp(transform, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
177 // Note width/height are flipped since we are rotating 90 degrees:
178 BufferedImage rotatedImage = new BufferedImage(sourceHeight, sourceWidth, image.getType());
179 op.filter(image, rotatedImage);
180 return new BufferedImageMonochromeBitmapSource(rotatedImage,
182 sourceWidth - (left + width),
187 public boolean isRotateSupported() {
188 // Can't run AffineTransforms on images of unknown format
189 return image.getType() != BufferedImage.TYPE_CUSTOM;
193 * Extracts luminance from a pixel from this source. By default, the source is assumed to use RGB,
194 * so this implementation computes luminance is a function of a red, green and blue components as
197 * <code>Y = 0.299R + 0.587G + 0.114B</code>
199 * where R, G, and B are values in [0,1].
201 private static int computeRGBLuminance(int pixel) {
202 // Coefficients add up to 1024 to make the divide into a fast shift
203 return (306 * ((pixel >> 16) & 0xFF) +
204 601 * ((pixel >> 8) & 0xFF) +
205 117 * (pixel & 0xFF)) >> 10;