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diff --git a/libraries/zxing/src/com/google/zxing/common/GridSampler.java b/libraries/zxing/src/com/google/zxing/common/GridSampler.java
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+++ b/libraries/zxing/src/com/google/zxing/common/GridSampler.java
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+/*
+ * Copyright 2007 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.NotFoundException;
+
+/**
+ * Implementations of this class can, given locations of finder patterns for a QR code in an
+ * image, sample the right points in the image to reconstruct the QR code, accounting for
+ * perspective distortion. It is abstracted since it is relatively expensive and should be allowed
+ * to take advantage of platform-specific optimized implementations, like Sun's Java Advanced
+ * Imaging library, but which may not be available in other environments such as J2ME, and vice
+ * versa.
+ *
+ * The implementation used can be controlled by calling {@link #setGridSampler(GridSampler)}
+ * with an instance of a class which implements this interface.
+ *
+ * @author Sean Owen
+ */
+public abstract class GridSampler {
+
+  private static GridSampler gridSampler = new DefaultGridSampler();
+
+  /**
+   * Sets the implementation of GridSampler used by the library. One global
+   * instance is stored, which may sound problematic. But, the implementation provided
+   * ought to be appropriate for the entire platform, and all uses of this library
+   * in the whole lifetime of the JVM. For instance, an Android activity can swap in
+   * an implementation that takes advantage of native platform libraries.
+   * 
+   * @param newGridSampler The platform-specific object to install.
+   */
+  public static void setGridSampler(GridSampler newGridSampler) {
+    if (newGridSampler == null) {
+      throw new IllegalArgumentException();
+    }
+    gridSampler = newGridSampler;
+  }
+
+  /**
+   * @return the current implementation of GridSampler
+   */
+  public static GridSampler getInstance() {
+    return gridSampler;
+  }
+
+  /**
+   * Samples an image for a rectangular matrix of bits of the given dimension.
+   * @param image image to sample
+   * @param dimensionX width of {@link BitMatrix} to sample from image
+   * @param dimensionY height of {@link BitMatrix} to sample from image
+   * @return {@link BitMatrix} representing a grid of points sampled from the image within a region
+   *   defined by the "from" parameters
+   * @throws NotFoundException if image can't be sampled, for example, if the transformation defined
+   *   by the given points is invalid or results in sampling outside the image boundaries
+   */
+  public abstract BitMatrix sampleGrid(BitMatrix image,
+                                       int dimensionX,
+                                       int dimensionY,
+                                       float p1ToX, float p1ToY,
+                                       float p2ToX, float p2ToY,
+                                       float p3ToX, float p3ToY,
+                                       float p4ToX, float p4ToY,
+                                       float p1FromX, float p1FromY,
+                                       float p2FromX, float p2FromY,
+                                       float p3FromX, float p3FromY,
+                                       float p4FromX, float p4FromY) throws NotFoundException;
+  
+  public abstract BitMatrix sampleGrid(BitMatrix image,
+                                       int dimensionX,
+                                       int dimensionY,
+                                       PerspectiveTransform transform) throws NotFoundException;
+
+  /**
+   * <p>Checks a set of points that have been transformed to sample points on an image against
+   * the image's dimensions to see if the point are even within the image.</p>
+   *
+   * <p>This method will actually "nudge" the endpoints back onto the image if they are found to be
+   * barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder
+   * patterns in an image where the QR Code runs all the way to the image border.</p>
+   *
+   * <p>For efficiency, the method will check points from either end of the line until one is found
+   * to be within the image. Because the set of points are assumed to be linear, this is valid.</p>
+   *
+   * @param image image into which the points should map
+   * @param points actual points in x1,y1,...,xn,yn form
+   * @throws NotFoundException if an endpoint is lies outside the image boundaries
+   */
+  protected static void checkAndNudgePoints(BitMatrix image, float[] points) throws NotFoundException {
+    int width = image.getWidth();
+    int height = image.getHeight();
+    // Check and nudge points from start until we see some that are OK:
+    boolean nudged = true;
+    for (int offset = 0; offset < points.length && nudged; offset += 2) {
+      int x = (int) points[offset];
+      int y = (int) points[offset + 1];
+      if (x < -1 || x > width || y < -1 || y > height) {
+        throw NotFoundException.getNotFoundInstance();
+      }
+      nudged = false;
+      if (x == -1) {
+        points[offset] = 0.0f;
+        nudged = true;
+      } else if (x == width) {
+        points[offset] = width - 1;
+        nudged = true;
+      }
+      if (y == -1) {
+        points[offset + 1] = 0.0f;
+        nudged = true;
+      } else if (y == height) {
+        points[offset + 1] = height - 1;
+        nudged = true;
+      }
+    }
+    // Check and nudge points from end:
+    nudged = true;
+    for (int offset = points.length - 2; offset >= 0 && nudged; offset -= 2) {
+      int x = (int) points[offset];
+      int y = (int) points[offset + 1];
+      if (x < -1 || x > width || y < -1 || y > height) {
+        throw NotFoundException.getNotFoundInstance();
+      }
+      nudged = false;
+      if (x == -1) {
+        points[offset] = 0.0f;
+        nudged = true;
+      } else if (x == width) {
+        points[offset] = width - 1;
+        nudged = true;
+      }
+      if (y == -1) {
+        points[offset + 1] = 0.0f;
+        nudged = true;
+      } else if (y == height) {
+        points[offset + 1] = height - 1;
+        nudged = true;
+      }
+    }
+  }
+
+}