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 int blackPoint;
38 private BlackPointEstimationMethod lastMethod;
39 private int lastArgument;
41 private static final int LUMINANCE_BITS = 5;
42 private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
43 private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
45 YUVMonochromeBitmapSource(Bitmap image) {
52 public boolean isBlack(int x, int y) {
53 return ((image.getPixel(x, y) >> 16) & 0xFF) < blackPoint;
56 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
58 row = new BitArray(getWidth);
62 int[] pixelRow = new int[getWidth];
63 image.getPixels(pixelRow, 0, getWidth, startX, y, getWidth, 1);
64 for (int i = 0; i < getWidth; i++) {
65 if (((pixelRow[i] >> 16) & 0xFF) < blackPoint) {
72 public int getHeight() {
73 return image.height();
76 public int getWidth() {
80 public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) {
81 if (!method.equals(lastMethod) || argument != lastArgument) {
82 int width = image.width();
83 int height = image.height();
84 int[] histogram = new int[LUMINANCE_BUCKETS];
85 float biasTowardsWhite = 1.0f;
86 if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
87 int minDimension = width < height ? width : height;
88 int startI = height == minDimension ? 0 : (height - width) >> 1;
89 int startJ = width == minDimension ? 0 : (width - height) >> 1;
90 for (int n = 0; n < minDimension; n++) {
91 int pixel = image.getPixel(startJ + n, startI + n);
92 histogram[((pixel >> 16) & 0xFF) >> LUMINANCE_SHIFT]++;
94 } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
95 if (argument < 0 || argument >= height) {
96 throw new IllegalArgumentException("Row is not within the image: " + argument);
98 biasTowardsWhite = 2.0f;
99 int[] pixelRow = new int[width];
100 image.getPixels(pixelRow, 0, width, 0, argument, width, 1);
101 for (int x = 0; x < width; x++) {
102 histogram[((pixelRow[x] >> 16) & 0xFF) >> LUMINANCE_SHIFT]++;
105 throw new IllegalArgumentException("Unknown method: " + method);
107 blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
109 lastArgument = argument;
113 public BlackPointEstimationMethod getLastEstimationMethod() {