Improved datamatrix reader with new algorithm

[zxing.git] / core / src / com / google / zxing / ResultPoint.java

diff --git a/core/src/com/google/zxing/ResultPoint.java b/core/src/com/google/zxing/ResultPoint.java
index a65e0f5..0c8e883 100644 (file)
--- a/core/src/com/google/zxing/ResultPoint.java
+++ b/core/src/com/google/zxing/ResultPoint.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2007 Google Inc.
+ * 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.
@@ -19,12 +19,109 @@ package com.google.zxing;
 /**
  * <p>Encapsulates a point of interest in an image containing a barcode. Typically, this
  * would be the location of a finder pattern or the corner of the barcode, for example.</p>
- * 
- * @author srowen@google.com (Sean Owen)
+ *
+ * @author Sean Owen
  */
-public interface ResultPoint {
+public class ResultPoint {
+
+  private final float x;
+  private final float y;
+
+  public ResultPoint(float x, float y) {
+    this.x = x;
+    this.y = y;
+  }
+
+  public final float getX() {
+    return x;
+  }
+
+  public final float getY() {
+    return y;
+  }
+
+  public boolean equals(Object other) {
+    if (other instanceof ResultPoint) {
+      ResultPoint otherPoint = (ResultPoint) other;
+      return x == otherPoint.x && y == otherPoint.y;
+    }
+    return false;
+  }
+
+  public int hashCode() {
+    return 31 * Float.floatToIntBits(x) + Float.floatToIntBits(y);
+  }
+
+  public String toString() {
+    StringBuffer result = new StringBuffer(25);
+    result.append('(');
+    result.append(x);
+    result.append(',');
+    result.append(y);
+    result.append(')');
+    return result.toString();
+  }
+
+  /**
+   * <p>Orders an array of three ResultPoints in an order [A,B,C] such that AB < AC and
+   * BC < AC and the angle between BC and BA is less than 180 degrees.
+   */
+  public static void orderBestPatterns(ResultPoint[] patterns) {
+
+    // Find distances between pattern centers
+    float zeroOneDistance = distance(patterns[0], patterns[1]);
+    float oneTwoDistance = distance(patterns[1], patterns[2]);
+    float zeroTwoDistance = distance(patterns[0], patterns[2]);
+
+    ResultPoint pointA, pointB, pointC;
+    // Assume one closest to other two is B; A and C will just be guesses at first
+    if (oneTwoDistance >= zeroOneDistance && oneTwoDistance >= zeroTwoDistance) {
+      pointB = patterns[0];
+      pointA = patterns[1];
+      pointC = patterns[2];
+    } else if (zeroTwoDistance >= oneTwoDistance && zeroTwoDistance >= zeroOneDistance) {
+      pointB = patterns[1];
+      pointA = patterns[0];
+      pointC = patterns[2];
+    } else {
+      pointB = patterns[2];
+      pointA = patterns[0];
+      pointC = patterns[1];
+    }
+
+    // Use cross product to figure out whether A and C are correct or flipped.
+    // This asks whether BC x BA has a positive z component, which is the arrangement
+    // we want for A, B, C. If it's negative, then we've got it flipped around and
+    // should swap A and C.
+    if (crossProductZ(pointA, pointB, pointC) < 0.0f) {
+      ResultPoint temp = pointA;
+      pointA = pointC;
+      pointC = temp;
+    }
+
+    patterns[0] = pointA;
+    patterns[1] = pointB;
+    patterns[2] = pointC;
+  }
+
+
+  /**
+   * @return distance between two points
+   */
+  public static float distance(ResultPoint pattern1, ResultPoint pattern2) {
+    float xDiff = pattern1.getX() - pattern2.getX();
+    float yDiff = pattern1.getY() - pattern2.getY();
+    return (float) Math.sqrt((double) (xDiff * xDiff + yDiff * yDiff));
+  }
+
+  /**
+   * Returns the z component of the cross product between vectors BC and BA.
+   */
+  private static float crossProductZ(ResultPoint pointA, ResultPoint pointB, ResultPoint pointC) {
+    float bX = pointB.x;
+    float bY = pointB.y;
+    return ((pointC.x - bX) * (pointA.y - bY)) - ((pointC.y - bY) * (pointA.x - bX));
+  }
 
-  float getX();
-  float getY();
 
 }