1 files changed, 279 insertions, 0 deletions
diff --git a/libraries/zxing/src/com/google/zxing/qrcode/detector/AlignmentPatternFinder.java b/libraries/zxing/src/com/google/zxing/qrcode/detector/AlignmentPatternFinder.java
new file mode 100644
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+++ b/libraries/zxing/src/com/google/zxing/qrcode/detector/AlignmentPatternFinder.java
@@ -0,0 +1,279 @@
+/*
+ * 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.qrcode.detector;
+
+import com.google.zxing.NotFoundException;
+import com.google.zxing.ResultPoint;
+import com.google.zxing.ResultPointCallback;
+import com.google.zxing.common.BitMatrix;
+
+import java.util.Vector;
+
+/**
+ * <p>This class attempts to find alignment patterns in a QR Code. Alignment patterns look like finder
+ * patterns but are smaller and appear at regular intervals throughout the image.</p>
+ *
+ * <p>At the moment this only looks for the bottom-right alignment pattern.</p>
+ *
+ * <p>This is mostly a simplified copy of {@link FinderPatternFinder}. It is copied,
+ * pasted and stripped down here for maximum performance but does unfortunately duplicate
+ * some code.</p>
+ *
+ * <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.
+ *
+ * @author Sean Owen
+ */
+final class AlignmentPatternFinder {
+
+  private final BitMatrix image;
+  private final Vector possibleCenters;
+  private final int startX;
+  private final int startY;
+  private final int width;
+  private final int height;
+  private final float moduleSize;
+  private final int[] crossCheckStateCount;
+  private final ResultPointCallback resultPointCallback;
+
+  /**
+   * <p>Creates a finder that will look in a portion of the whole image.</p>
+   *
+   * @param image image to search
+   * @param startX left column from which to start searching
+   * @param startY top row from which to start searching
+   * @param width width of region to search
+   * @param height height of region to search
+   * @param moduleSize estimated module size so far
+   */
+  AlignmentPatternFinder(BitMatrix image,
+                         int startX,
+                         int startY,
+                         int width,
+                         int height,
+                         float moduleSize,
+                         ResultPointCallback resultPointCallback) {
+    this.image = image;
+    this.possibleCenters = new Vector(5);
+    this.startX = startX;
+    this.startY = startY;
+    this.width = width;
+    this.height = height;
+    this.moduleSize = moduleSize;
+    this.crossCheckStateCount = new int[3];
+    this.resultPointCallback = resultPointCallback;
+  }
+
+  /**
+   * <p>This method attempts to find the bottom-right alignment pattern in the image. It is a bit messy since
+   * it's pretty performance-critical and so is written to be fast foremost.</p>
+   *
+   * @return {@link AlignmentPattern} if found
+   * @throws NotFoundException if not found
+   */
+  AlignmentPattern find() throws NotFoundException {
+    int startX = this.startX;
+    int height = this.height;
+    int maxJ = startX + width;
+    int middleI = startY + (height >> 1);
+    // We are looking for black/white/black modules in 1:1:1 ratio;
+    // this tracks the number of black/white/black modules seen so far
+    int[] stateCount = new int[3];
+    for (int iGen = 0; iGen < height; iGen++) {
+      // Search from middle outwards
+      int i = middleI + ((iGen & 0x01) == 0 ? (iGen + 1) >> 1 : -((iGen + 1) >> 1));
+      stateCount[0] = 0;
+      stateCount[1] = 0;
+      stateCount[2] = 0;
+      int j = startX;
+      // Burn off leading white pixels before anything else; if we start in the middle of
+      // a white run, it doesn't make sense to count its length, since we don't know if the
+      // white run continued to the left of the start point
+      while (j < maxJ && !image.get(j, i)) {
+        j++;
+      }
+      int currentState = 0;
+      while (j < maxJ) {
+        if (image.get(j, i)) {
+          // Black pixel
+          if (currentState == 1) { // Counting black pixels
+            stateCount[currentState]++;
+          } else { // Counting white pixels
+            if (currentState == 2) { // A winner?
+              if (foundPatternCross(stateCount)) { // Yes
+                AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, j);
+                if (confirmed != null) {
+                  return confirmed;
+                }
+              }
+              stateCount[0] = stateCount[2];
+              stateCount[1] = 1;
+              stateCount[2] = 0;
+              currentState = 1;
+            } else {
+              stateCount[++currentState]++;
+            }
+          }
+        } else { // White pixel
+          if (currentState == 1) { // Counting black pixels
+            currentState++;
+          }
+          stateCount[currentState]++;
+        }
+        j++;
+      }
+      if (foundPatternCross(stateCount)) {
+        AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, maxJ);
+        if (confirmed != null) {
+          return confirmed;
+        }
+      }
+
+    }
+
+    // Hmm, nothing we saw was observed and confirmed twice. If we had
+    // any guess at all, return it.
+    if (!possibleCenters.isEmpty()) {
+      return (AlignmentPattern) possibleCenters.elementAt(0);
+    }
+
+    throw NotFoundException.getNotFoundInstance();
+  }
+
+  /**
+   * Given a count of black/white/black pixels just seen and an end position,
+   * figures the location of the center of this black/white/black run.
+   */
+  private static float centerFromEnd(int[] stateCount, int end) {
+    return (float) (end - stateCount[2]) - stateCount[1] / 2.0f;
+  }
+
+  /**
+   * @param stateCount count of black/white/black pixels just read
+   * @return true iff the proportions of the counts is close enough to the 1/1/1 ratios
+   *         used by alignment patterns to be considered a match
+   */
+  private boolean foundPatternCross(int[] stateCount) {
+    float moduleSize = this.moduleSize;
+    float maxVariance = moduleSize / 2.0f;
+    for (int i = 0; i < 3; i++) {
+      if (Math.abs(moduleSize - stateCount[i]) >= maxVariance) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  /**
+   * <p>After a horizontal scan finds a potential alignment pattern, this method
+   * "cross-checks" by scanning down vertically through the center of the possible
+   * alignment pattern to see if the same proportion is detected.</p>
+   *
+   * @param startI row where an alignment pattern was detected
+   * @param centerJ center of the section that appears to cross an alignment pattern
+   * @param maxCount maximum reasonable number of modules that should be
+   * observed in any reading state, based on the results of the horizontal scan
+   * @return vertical center of alignment pattern, or {@link Float#NaN} if not found
+   */
+  private float crossCheckVertical(int startI, int centerJ, int maxCount,
+      int originalStateCountTotal) {
+    BitMatrix image = this.image;
+
+    int maxI = image.getHeight();
+    int[] stateCount = crossCheckStateCount;
+    stateCount[0] = 0;
+    stateCount[1] = 0;
+    stateCount[2] = 0;
+
+    // Start counting up from center
+    int i = startI;
+    while (i >= 0 && image.get(centerJ, i) && stateCount[1] <= maxCount) {
+      stateCount[1]++;
+      i--;
+    }
+    // If already too many modules in this state or ran off the edge:
+    if (i < 0 || stateCount[1] > maxCount) {
+      return Float.NaN;
+    }
+    while (i >= 0 && !image.get(centerJ, i) && stateCount[0] <= maxCount) {
+      stateCount[0]++;
+      i--;
+    }
+    if (stateCount[0] > maxCount) {
+      return Float.NaN;
+    }
+
+    // Now also count down from center
+    i = startI + 1;
+    while (i < maxI && image.get(centerJ, i) && stateCount[1] <= maxCount) {
+      stateCount[1]++;
+      i++;
+    }
+    if (i == maxI || stateCount[1] > maxCount) {
+      return Float.NaN;
+    }
+    while (i < maxI && !image.get(centerJ, i) && stateCount[2] <= maxCount) {
+      stateCount[2]++;
+      i++;
+    }
+    if (stateCount[2] > maxCount) {
+      return Float.NaN;
+    }
+
+    int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
+    if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
+      return Float.NaN;
+    }
+
+    return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : Float.NaN;
+  }
+
+  /**
+   * <p>This is called when a horizontal scan finds a possible alignment pattern. It will
+   * cross check with a vertical scan, and if successful, will see if this pattern had been
+   * found on a previous horizontal scan. If so, we consider it confirmed and conclude we have
+   * found the alignment pattern.</p>
+   *
+   * @param stateCount reading state module counts from horizontal scan
+   * @param i row where alignment pattern may be found
+   * @param j end of possible alignment pattern in row
+   * @return {@link AlignmentPattern} if we have found the same pattern twice, or null if not
+   */
+  private AlignmentPattern handlePossibleCenter(int[] stateCount, int i, int j) {
+    int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];
+    float centerJ = centerFromEnd(stateCount, j);
+    float centerI = crossCheckVertical(i, (int) centerJ, 2 * stateCount[1], stateCountTotal);
+    if (!Float.isNaN(centerI)) {
+      float estimatedModuleSize = (float) (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0f;
+      int max = possibleCenters.size();
+      for (int index = 0; index < max; index++) {
+        AlignmentPattern center = (AlignmentPattern) possibleCenters.elementAt(index);
+        // Look for about the same center and module size:
+        if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
+          return new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
+        }
+      }
+      // Hadn't found this before; save it
+      ResultPoint point = new AlignmentPattern(centerJ, centerI, estimatedModuleSize);
+      possibleCenters.addElement(point);
+      if (resultPointCallback != null) {
+        resultPointCallback.foundPossibleResultPoint(point);
+      }
+    }
+    return null;
+  }
+
+}