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.j2me;
19 import com.google.zxing.MonochromeBitmapSource;
20 import com.google.zxing.BlackPointEstimationMethod;
21 import com.google.zxing.common.BitArray;
22 import com.google.zxing.common.BlackPointEstimator;
24 import javax.microedition.lcdui.Image;
27 * <p>An implementation based on Java ME's {@link Image} representation.</p>
29 * @author Sean Owen (srowen@google.com), Daniel Switkin (dswitkin@google.com)
31 final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
33 private final int[] rgbPixels;
34 private final int width;
35 private final int height;
36 private int blackPoint;
37 private BlackPointEstimationMethod lastMethod;
39 LCDUIImageMonochromeBitmapSource(final Image image) {
40 width = image.getWidth();
41 height = image.getHeight();
42 rgbPixels = new int[width * height];
43 image.getRGB(rgbPixels, 0, width, 0, 0, width, height);
47 public boolean isBlack(int x, int y) {
48 return computeRGBLuminance(rgbPixels[x + y * width]) < blackPoint;
51 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
53 row = new BitArray(getWidth);
57 for (int i = 0, offset = y * width + startX; i < getWidth; i++, offset++) {
58 if (computeRGBLuminance(rgbPixels[offset]) < blackPoint) {
65 public int getHeight() {
69 public int getWidth() {
73 public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) {
74 if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
75 if (!BlackPointEstimationMethod.TWO_D_SAMPLING.equals(lastMethod)) {
76 int[] luminanceBuckets = new int[32];
77 int minDimension = width < height ? width : height;
78 for (int n = 0, offset = 0; n < minDimension; n++, offset += width + 1) {
79 luminanceBuckets[computeRGBLuminance(rgbPixels[offset]) >> 3]++;
81 blackPoint = BlackPointEstimator.estimate(luminanceBuckets) << 3;
83 } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
86 throw new IllegalArgumentException("Unknown method: " + method);
91 public BlackPointEstimationMethod getLastEstimationMethod() {
96 * Extracts luminance from a pixel from this source. By default, the source is assumed to use RGB,
97 * so this implementation computes luminance is a function of a red, green and blue components as
100 * <code>Y = 0.299R + 0.587G + 0.114B</code>
102 * where R, G, and B are values in [0,1].
104 private static int computeRGBLuminance(int pixel) {
105 // Coefficients add up to 1024 to make the divide into a fast shift
106 return (306 * ((pixel >> 16) & 0xFF) +
107 601 * ((pixel >> 8) & 0xFF) +
108 117 * (pixel & 0xFF)) >> 10;