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diff --git a/OpenPGP-Keychain/src/com/google/zxing/common/HybridBinarizer.java b/OpenPGP-Keychain/src/com/google/zxing/common/HybridBinarizer.java
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+/*
+ * Copyright 2009 ZXing authors
+ *
+ * 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.common;
+
+import com.google.zxing.Binarizer;
+import com.google.zxing.LuminanceSource;
+import com.google.zxing.NotFoundException;
+
+/**
+ * This class implements a local thresholding algorithm, which while slower than the
+ * GlobalHistogramBinarizer, is fairly efficient for what it does. It is designed for
+ * high frequency images of barcodes with black data on white backgrounds. For this application,
+ * it does a much better job than a global blackpoint with severe shadows and gradients.
+ * However it tends to produce artifacts on lower frequency images and is therefore not
+ * a good general purpose binarizer for uses outside ZXing.
+ *
+ * This class extends GlobalHistogramBinarizer, using the older histogram approach for 1D readers,
+ * and the newer local approach for 2D readers. 1D decoding using a per-row histogram is already
+ * inherently local, and only fails for horizontal gradients. We can revisit that problem later,
+ * but for now it was not a win to use local blocks for 1D.
+ *
+ * This Binarizer is the default for the unit tests and the recommended class for library users.
+ *
+ * @author dswitkin@google.com (Daniel Switkin)
+ */
+public final class HybridBinarizer extends GlobalHistogramBinarizer {
+
+  // This class uses 5x5 blocks to compute local luminance, where each block is 8x8 pixels.
+  // So this is the smallest dimension in each axis we can accept.
+  private static final int MINIMUM_DIMENSION = 40;
+
+  private BitMatrix matrix = null;
+
+  public HybridBinarizer(LuminanceSource source) {
+    super(source);
+  }
+
+  public BitMatrix getBlackMatrix() throws NotFoundException {
+    binarizeEntireImage();
+    return matrix;
+  }
+
+  public Binarizer createBinarizer(LuminanceSource source) {
+    return new HybridBinarizer(source);
+  }
+
+  // Calculates the final BitMatrix once for all requests. This could be called once from the
+  // constructor instead, but there are some advantages to doing it lazily, such as making
+  // profiling easier, and not doing heavy lifting when callers don't expect it.
+  private void binarizeEntireImage() throws NotFoundException {
+    if (matrix == null) {
+      LuminanceSource source = getLuminanceSource();
+      if (source.getWidth() >= MINIMUM_DIMENSION && source.getHeight() >= MINIMUM_DIMENSION) {
+        byte[] luminances = source.getMatrix();
+        int width = source.getWidth();
+        int height = source.getHeight();
+        int subWidth = width >> 3;
+        if ((width & 0x07) != 0) {
+          subWidth++;
+        }
+        int subHeight = height >> 3;
+        if ((height & 0x07) != 0) {
+          subHeight++;
+        }
+        int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
+
+        matrix = new BitMatrix(width, height);
+        calculateThresholdForBlock(luminances, subWidth, subHeight, width, height, blackPoints, matrix);
+      } else {
+        // If the image is too small, fall back to the global histogram approach.
+        matrix = super.getBlackMatrix();
+      }
+    }
+  }
+
+  // For each 8x8 block in the image, calculate the average black point using a 5x5 grid
+  // of the blocks around it. Also handles the corner cases (fractional blocks are computed based
+  // on the last 8 pixels in the row/column which are also used in the previous block).
+  private static void calculateThresholdForBlock(byte[] luminances, int subWidth, int subHeight,
+      int width, int height, int[][] blackPoints, BitMatrix matrix) {
+    for (int y = 0; y < subHeight; y++) {
+      int yoffset = y << 3;
+      if ((yoffset + 8) >= height) {
+        yoffset = height - 8;
+      }
+      for (int x = 0; x < subWidth; x++) {
+        int xoffset = x << 3;
+        if ((xoffset + 8) >= width) {
+            xoffset = width - 8;
+        }
+        int left = x > 1 ? x : 2;
+        left = left < subWidth - 2 ? left : subWidth - 3;
+        int top = y > 1 ? y : 2;
+        top = top < subHeight - 2 ? top : subHeight - 3;
+        int sum = 0;
+        for (int z = -2; z <= 2; z++) {
+          int[] blackRow = blackPoints[top + z];
+          sum += blackRow[left - 2];
+          sum += blackRow[left - 1];
+          sum += blackRow[left];
+          sum += blackRow[left + 1];
+          sum += blackRow[left + 2];
+        }
+        int average = sum / 25;
+        threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix);
+      }
+    }
+  }
+
+  // Applies a single threshold to an 8x8 block of pixels.
+  private static void threshold8x8Block(byte[] luminances, int xoffset, int yoffset, int threshold,
+      int stride, BitMatrix matrix) {
+    for (int y = 0; y < 8; y++) {
+      int offset = (yoffset + y) * stride + xoffset;
+      for (int x = 0; x < 8; x++) {
+        int pixel = luminances[offset + x] & 0xff;
+        if (pixel < threshold) {
+          matrix.set(xoffset + x, yoffset + y);
+        }
+      }
+    }
+  }
+
+  // Calculates a single black point for each 8x8 block of pixels and saves it away.
+  private static int[][] calculateBlackPoints(byte[] luminances, int subWidth, int subHeight,
+      int width, int height) {
+    int[][] blackPoints = new int[subHeight][subWidth];
+    for (int y = 0; y < subHeight; y++) {
+      int yoffset = y << 3;
+      if ((yoffset + 8) >= height) {
+        yoffset = height - 8;
+      }
+      for (int x = 0; x < subWidth; x++) {
+        int xoffset = x << 3;
+        if ((xoffset + 8) >= width) {
+            xoffset = width - 8;
+        }
+        int sum = 0;
+        int min = 255;
+        int max = 0;
+        for (int yy = 0; yy < 8; yy++) {
+          int offset = (yoffset + yy) * width + xoffset;
+          for (int xx = 0; xx < 8; xx++) {
+            int pixel = luminances[offset + xx] & 0xff;
+            sum += pixel;
+            if (pixel < min) {
+              min = pixel;
+            }
+            if (pixel > max) {
+              max = pixel;
+            }
+          }
+        }
+
+        // If the contrast is inadequate, use half the minimum, so that this block will be
+        // treated as part of the white background, but won't drag down neighboring blocks
+        // too much.
+        int average;
+        if (max - min > 24) {
+          average = sum >> 6;
+        } else {
+          // When min == max == 0, let average be 1 so all is black
+          average = max == 0 ? 1 : min >> 1;
+        }
+        blackPoints[y][x] = average;
+      }
+    }
+    return blackPoints;
+  }
+
+}