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diff --git a/OpenPGP-Keychain/src/com/google/zxing/Binarizer.java b/OpenPGP-Keychain/src/com/google/zxing/Binarizer.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;
+
+import com.google.zxing.common.BitArray;
+import com.google.zxing.common.BitMatrix;
+
+/**
+ * This class hierarchy provides a set of methods to convert luminance data to 1 bit data.
+ * It allows the algorithm to vary polymorphically, for example allowing a very expensive
+ * thresholding technique for servers and a fast one for mobile. It also permits the implementation
+ * to vary, e.g. a JNI version for Android and a Java fallback version for other platforms.
+ *
+ * @author dswitkin@google.com (Daniel Switkin)
+ */
+public abstract class Binarizer {
+
+  private final LuminanceSource source;
+
+  protected Binarizer(LuminanceSource source) {
+    if (source == null) {
+      throw new IllegalArgumentException("Source must be non-null.");
+    }
+    this.source = source;
+  }
+
+  public LuminanceSource getLuminanceSource() {
+    return source;
+  }
+
+  /**
+   * Converts one row of luminance data to 1 bit data. May actually do the conversion, or return
+   * cached data. Callers should assume this method is expensive and call it as seldom as possible.
+   * This method is intended for decoding 1D barcodes and may choose to apply sharpening.
+   * For callers which only examine one row of pixels at a time, the same BitArray should be reused
+   * and passed in with each call for performance. However it is legal to keep more than one row
+   * at a time if needed.
+   *
+   * @param y The row to fetch, 0 <= y < bitmap height.
+   * @param row An optional preallocated array. If null or too small, it will be ignored.
+   *            If used, the Binarizer will call BitArray.clear(). Always use the returned object.
+   * @return The array of bits for this row (true means black).
+   */
+  public abstract BitArray getBlackRow(int y, BitArray row) throws NotFoundException;
+
+  /**
+   * Converts a 2D array of luminance data to 1 bit data. As above, assume this method is expensive
+   * and do not call it repeatedly. This method is intended for decoding 2D barcodes and may or
+   * may not apply sharpening. Therefore, a row from this matrix may not be identical to one
+   * fetched using getBlackRow(), so don't mix and match between them.
+   *
+   * @return The 2D array of bits for the image (true means black).
+   */
+  public abstract BitMatrix getBlackMatrix() throws NotFoundException;
+
+  /**
+   * Creates a new object with the same type as this Binarizer implementation, but with pristine
+   * state. This is needed because Binarizer implementations may be stateful, e.g. keeping a cache
+   * of 1 bit data. See Effective Java for why we can't use Java's clone() method.
+   *
+   * @param source The LuminanceSource this Binarizer will operate on.
+   * @return A new concrete Binarizer implementation object.
+   */
+  public abstract Binarizer createBinarizer(LuminanceSource source);
+
+}