Switch to RGB-based captures for decoding, in preparation for move to continuous scan model

git-svn-id: https://zxing.googlecode.com/svn/trunk@262 59b500cc-1b3d-0410-9834-0bbf25fbcc57

android/src/com/google/zxing/client/android/CameraManager.java

@@ -157,7 +157,7 @@ final class CameraManager {
         params.topPixel = (cameraResolution.y - params.srcHeight) / 2;
         params.outputWidth = stillResolution.x;
         params.outputHeight = stillResolution.y;
-        params.dataFormat = 0; // YUV packed (planar would be better, but it doesn't work right now)
+        params.dataFormat = 2; // RGB565
       }
       String captureType = on ? "preview" : "still";
       Log.v(TAG, "Setting params for " + captureType + ": srcWidth " + params.srcWidth +

android/src/com/google/zxing/client/android/RGBMonochromeBitmapSource.java

@@ -0,0 +1,149 @@
+/*
+ * 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.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) {
+    if (!method.equals(lastMethod) || argument != lastArgument) {
+      int width = image.width();
+      int height = image.height();
+      int[] histogram = new int[LUMINANCE_BUCKETS];
+      float biasTowardsWhite = 1.0f;
+      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);
+        }
+        biasTowardsWhite = 2.0f;
+        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, biasTowardsWhite) << 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;
+  }
+
+}

android/src/com/google/zxing/client/android/WorkerThread.java

@@ -67,7 +67,7 @@ final class WorkerThread extends Thread {
           Bitmap bitmap = cameraManager.captureStill();
           Result rawResult;
           try {
-            MonochromeBitmapSource source = new YUVMonochromeBitmapSource(bitmap);
+            MonochromeBitmapSource source = new RGBMonochromeBitmapSource(bitmap);
             rawResult = new MultiFormatReader().decode(source);
           } catch (ReaderException e) {
             Message message = Message.obtain(handler, R.id.decoding_failed_message);