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 * @author srowen@google.com (Sean Owen), Daniel Switkin (dswitkin@google.com)
37 public final class BufferedImageMonochromeBitmapSource implements MonochromeBitmapSource {
39 private final BufferedImage image;
40 private int blackPoint;
41 private BlackPointEstimationMethod lastMethod;
42 private int lastArgument;
44 private static final int LUMINANCE_BITS = 5;
45 private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
46 private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
48 public BufferedImageMonochromeBitmapSource(BufferedImage image) {
55 public BufferedImage getImage() {
59 public boolean isBlack(int x, int y) {
60 return computeRGBLuminance(image.getRGB(x, y)) < blackPoint;
63 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
65 row = new BitArray(getWidth);
69 int[] pixelRow = image.getRGB(startX, y, getWidth, 1, null, 0, getWidth);
70 for (int i = 0; i < getWidth; i++) {
71 if (computeRGBLuminance(pixelRow[i]) < blackPoint) {
78 public int getHeight() {
79 return image.getHeight();
82 public int getWidth() {
83 return image.getWidth();
86 public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException {
87 if (!method.equals(lastMethod) || argument != lastArgument) {
88 int width = image.getWidth();
89 int height = image.getHeight();
90 int[] histogram = new int[LUMINANCE_BUCKETS];
91 float biasTowardsWhite = 1.0f;
92 if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
93 int minDimension = width < height ? width : height;
94 int startI = height == minDimension ? 0 : (height - width) >> 1;
95 int startJ = width == minDimension ? 0 : (width - height) >> 1;
96 for (int n = 0; n < minDimension; n++) {
97 int pixel = image.getRGB(startJ + n, startI + n);
98 histogram[computeRGBLuminance(pixel) >> LUMINANCE_SHIFT]++;
100 } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
101 if (argument < 0 || argument >= height) {
102 throw new IllegalArgumentException("Row is not within the image: " + argument);
104 biasTowardsWhite = 2.0f;
105 int[] rgbArray = new int[width];
106 image.getRGB(0, argument, width, 1, rgbArray, 0, width);
107 for (int x = 0; x < width; x++) {
108 histogram[computeRGBLuminance(rgbArray[x]) >> LUMINANCE_SHIFT]++;
111 throw new IllegalArgumentException("Unknown method: " + method);
113 blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
115 lastArgument = argument;
119 public BlackPointEstimationMethod getLastEstimationMethod() {
123 public MonochromeBitmapSource rotateCounterClockwise() {
124 if (!isRotateSupported()) {
125 throw new IllegalStateException("Rotate not supported");
127 // 90 degrees counterclockwise:
128 AffineTransform transform = new AffineTransform(0.0, -1.0, 1.0, 0.0, 0.0, image.getWidth());
129 BufferedImageOp op = new AffineTransformOp(transform, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
130 // Note width/height are flipped since we are rotating 90 degrees:
131 BufferedImage rotatedImage = new BufferedImage(image.getHeight(), image.getWidth(), image.getType());
132 op.filter(image, rotatedImage);
133 return new BufferedImageMonochromeBitmapSource(rotatedImage);
136 public boolean isRotateSupported() {
137 // Can't run AffineTransforms on images of unknown format
138 return image.getType() != BufferedImage.TYPE_CUSTOM;
142 * Extracts luminance from a pixel from this source. By default, the source is assumed to use RGB,
143 * so this implementation computes luminance is a function of a red, green and blue components as
146 * <code>Y = 0.299R + 0.587G + 0.114B</code>
148 * where R, G, and B are values in [0,1].
150 private static int computeRGBLuminance(int pixel) {
151 // Coefficients add up to 1024 to make the divide into a fast shift
152 return (306 * ((pixel >> 16) & 0xFF) +
153 601 * ((pixel >> 8) & 0xFF) +
154 117 * (pixel & 0xFF)) >> 10;