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+/*
+ * Copyright (C) 2008 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.client.android;
+
+import android.graphics.Bitmap;
+import com.google.zxing.BlackPointEstimationMethod;
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
+import com.google.zxing.common.BitArray;
+import com.google.zxing.common.BlackPointEstimator;
+
+/**
+ * This object implements MonochromeBitmapSource around an Android Bitmap. Rather than capturing an
+ * RGB image and calculating the grey value at each pixel, we ask the camera driver for YUV data and
+ * strip out the luminance channel directly. This should be faster but provides fewer bits, i.e.
+ * fewer grey levels.
+ *
+ * @author dswitkin@google.com (Daniel Switkin)
+ * @author srowen@google.com (Sean Owen)
+ */
+final class RGBMonochromeBitmapSource implements MonochromeBitmapSource {
+
+ private final Bitmap image;
+ private int blackPoint;
+ private BlackPointEstimationMethod lastMethod;
+ private int lastArgument;
+
+ private static final int LUMINANCE_BITS = 5;
+ private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
+ private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
+
+ RGBMonochromeBitmapSource(Bitmap image) {
+ this.image = image;
+ blackPoint = 0x7F;
+ lastMethod = null;
+ lastArgument = 0;
+ }
+
+ public boolean isBlack(int x, int y) {
+ return computeRGBLuminance(image.getPixel(x, y)) < blackPoint;
+ }
+
+ public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
+ if (row == null) {
+ row = new BitArray(getWidth);
+ } else {
+ row.clear();
+ }
+ int[] pixelRow = new int[getWidth];
+ image.getPixels(pixelRow, 0, getWidth, startX, y, getWidth, 1);
+ for (int i = 0; i < getWidth; i++) {
+ if (computeRGBLuminance(pixelRow[i]) < blackPoint) {
+ row.set(i);
+ }
+ }
+ return row;
+ }
+
+ public int getHeight() {
+ return image.height();
+ }
+
+ public int getWidth() {
+ return image.width();
+ }
+
+ public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException {
+ if (!method.equals(lastMethod) || argument != lastArgument) {
+ int width = image.width();
+ int height = image.height();
+ int[] histogram = new int[LUMINANCE_BUCKETS];
+ if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
+ int minDimension = width < height ? width : height;
+ int startI = height == minDimension ? 0 : (height - width) >> 1;
+ int startJ = width == minDimension ? 0 : (width - height) >> 1;
+ for (int n = 0; n < minDimension; n++) {
+ int pixel = image.getPixel(startJ + n, startI + n);
+ histogram[computeRGBLuminance(pixel) >> LUMINANCE_SHIFT]++;
+ }
+ } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
+ if (argument < 0 || argument >= height) {
+ throw new IllegalArgumentException("Row is not within the image: " + argument);
+ }
+ int[] pixelRow = new int[width];
+ image.getPixels(pixelRow, 0, width, 0, argument, width, 1);
+ for (int x = 0; x < width; x++) {
+ histogram[computeRGBLuminance(pixelRow[x]) >> LUMINANCE_SHIFT]++;
+ }
+ } else {
+ throw new IllegalArgumentException("Unknown method: " + method);
+ }
+ blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
+ lastMethod = method;
+ lastArgument = argument;
+ }
+ }
+
+ public BlackPointEstimationMethod getLastEstimationMethod() {
+ return lastMethod;
+ }
+
+ public MonochromeBitmapSource rotateCounterClockwise() {
+ throw new IllegalStateException("Rotate not supported");
+ }
+
+ public boolean isRotateSupported() {
+ return false;
+ }
+
+ /**
+ * An optimized approximation of a more proper conversion from RGB to luminance which
+ * only uses shifts. See BufferedImageMonochromeBitmapSource for an original version.
+ */
+ private static int computeRGBLuminance(int pixel) {
+ // Instead of multiplying by 306, 601, 117, we multiply by 256, 512, 256, so that
+ // the multiplies can be implemented as shifts.
+ //
+ // Really, it's:
+ //
+ // return ((((pixel >> 16) & 0xFF) << 8) +
+ // (((pixel >> 8) & 0xFF) << 9) +
+ // (( pixel & 0xFF) << 8)) >> 10;
+ //
+ // That is, we're replacing the coefficients in the original with powers of two,
+ // which can be implemented as shifts, even though changing the coefficients slightly
+ // corrupts the conversion. Not significant for our purposes.
+ //
+ // But we can get even cleverer and eliminate a few shifts:
+ return (((pixel & 0x00FF0000) >> 8) +
+ ((pixel & 0x0000FF00) << 1) +
+ ((pixel & 0x000000FF) << 8)) >> 10;
+ }
+
+}
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