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.common.BitArray;
21 import com.google.zxing.common.BlackPointEstimator;
23 import javax.microedition.lcdui.Image;
26 * <p>An implementation based on Java ME's {@link Image} representation.</p>
28 * @author Sean Owen (srowen@google.com)
30 final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
32 private final int[] rgbPixels;
33 private final int blackPoint;
34 private final int width;
35 private final int height;
37 LCDUIImageMonochromeBitmapSource(final Image image) {
38 int width = image.getWidth();
39 int height = image.getHeight();
42 int[] rgbPixels = new int[width * height];
43 this.rgbPixels = rgbPixels;
44 image.getRGB(rgbPixels, 0, width, 0, 0, width, height);
45 int[] luminanceBuckets = new int[32];
46 int minDimension = width < height ? width : height;
47 for (int n = 0, offset = 0; n < minDimension; n++, offset += width + 1) {
48 luminanceBuckets[computeRGBLuminance(rgbPixels[offset]) >> 3]++;
50 blackPoint = BlackPointEstimator.estimate(luminanceBuckets) << 3;
53 public boolean isBlack(int x, int y) {
54 return computeRGBLuminance(rgbPixels[x + y * width]) < blackPoint;
57 public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
59 row = new BitArray(getWidth);
63 for (int i = 0, offset = y * width + startX; i < getWidth; i++, offset++) {
64 if (computeRGBLuminance(rgbPixels[offset]) < blackPoint) {
71 public int getHeight() {
75 public int getWidth() {
80 * Extracts luminance from a pixel from this source. By default, the source is assumed to use RGB,
81 * so this implementation computes luminance is a function of a red, green and blue components as
84 * <code>Y = 0.299R + 0.587G + 0.114B</code>
86 * where R, G, and B are values in [0,1].
88 private static int computeRGBLuminance(int pixel) {
89 // Coefficients add up to 1024 to make the divide into a fast shift
90 return (306 * ((pixel >> 16) & 0xFF) +
91 601 * ((pixel >> 8) & 0xFF) +
92 117 * (pixel & 0xFF)) >> 10;