2 * Copyright (C) 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.client.android;
19 import android.graphics.Bitmap;
20 import com.google.zxing.BlackPointEstimationMethod;
21 import com.google.zxing.MonochromeBitmapSource;
22 import com.google.zxing.common.BitArray;
23 import com.google.zxing.common.BlackPointEstimator;
26 * This object implements MonochromeBitmapSource around an Android Bitmap. Rather than capturing an
27 * RGB image and calculating the grey value at each pixel, we ask the camera driver for YUV data and
28 * strip out the luminance channel directly. This should be faster but provides fewer bits, i.e.
31 * @author dswitkin@google.com (Daniel Switkin)
32 * @author srowen@google.com (Sean Owen)
34 final class YUVMonochromeBitmapSource implements MonochromeBitmapSource {
36 private final Bitmap image;
37 private final BitArray[] blackWhitePixels;
38 private final int width;
39 private final int height;
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 YUVMonochromeBitmapSource(Bitmap image) {
49 width = image.width();
50 height = image.height();
52 blackWhitePixels = new BitArray[height];
58 public boolean isBlack(int x, int y) {
59 BitArray blackWhite = blackWhitePixels[y];
60 if (blackWhite == null) {
61 blackWhite = parseBlackWhite(y);
63 return blackWhite.get(x);
66 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
67 BitArray blackWhite = blackWhitePixels[y];
68 if (blackWhite == null) {
69 blackWhite = parseBlackWhite(y);
72 if (startX == 0 && getWidth == width) {
75 row = new BitArray(getWidth);
79 for (int i = 0; i < getWidth; i++) {
80 if (blackWhite.get(startX + i)) {
87 private BitArray parseBlackWhite(int y) {
88 int width = this.width;
89 int[] pixelRow = new int[width];
90 image.getPixels(pixelRow, 0, width, 0, y, width, 1);
91 BitArray luminanceRow = new BitArray(width);
92 int blackPoint = this.blackPoint;
93 // Calculate 32 bits at a time to more efficiently set the bit array
96 for (int j = 0; j < width; j++) {
98 // Computation of luminance is inlined here for speed:
99 if (((pixelRow[j] >> 16) & 0xFF) <= blackPoint) {
102 if (++bitCount == 32) {
103 luminanceRow.setBulk(j, bits);
109 luminanceRow.setBulk(width, bits >>> (32 - bitCount));
111 blackWhitePixels[y] = luminanceRow;
115 public int getHeight() {
119 public int getWidth() {
123 public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) {
124 if (!method.equals(lastMethod) || argument != lastArgument) {
125 for (int i = 0; i < blackWhitePixels.length; i++) {
126 blackWhitePixels[i] = null;
128 int[] histogram = new int[LUMINANCE_BUCKETS];
129 if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
130 int minDimension = width < height ? width : height;
131 int startI = height == minDimension ? 0 : (height - width) >> 1;
132 int startJ = width == minDimension ? 0 : (width - height) >> 1;
133 for (int n = 0; n < minDimension; n++) {
134 int pixel = image.getPixel(startJ + n, startI + n);
135 // Computation of luminance is inlined here for speed:
136 histogram[((pixel >> 16) & 0xFF) >> LUMINANCE_SHIFT]++;
138 } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
139 if (argument < 0 || argument >= height) {
140 throw new IllegalArgumentException("Row is not within the image: " + argument);
142 int[] yuvArray = new int[width];
143 image.getPixels(yuvArray, 0, width, 0, argument, width, 1);
144 for (int x = 0; x < width; x++) {
145 histogram[((yuvArray[x] >> 16) & 0xFF) >> LUMINANCE_SHIFT]++;
148 throw new IllegalArgumentException("Unknown method: " + method);
150 blackPoint = BlackPointEstimator.estimate(histogram, 1.0f) << LUMINANCE_SHIFT;
152 lastArgument = argument;
156 public BlackPointEstimationMethod getLastEstimationMethod() {