Fixed the rest of my typos and added basic unit test

git-svn-id: https://zxing.googlecode.com/svn/trunk@23 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/qrcode/detector/DefaultGridSampler.java

@@ -77,7 +77,7 @@ public final class DefaultGridSampler extends GridSampler {
       for (int j = 0; j < max; j += 2) {
         if (image.isBlack((int) points[j], (int) points[j + 1])) {
           // Black(-ish) pixel
-          bits.set(i, j);
+          bits.set(i, j >> 1);
         }
       }
     }

core/src/com/google/zxing/qrcode/detector/PerspectiveTransform.java

@@ -49,9 +49,11 @@ final class PerspectiveTransform {
                                                            float x1p, float y1p,
                                                            float x2p, float y2p,
                                                            float x3p, float y3p) {
-    return
+
-        quadrilateralToSquare(x0, y0, x1, y1, x2, y2, x3, y3).times(
+    PerspectiveTransform qToS = quadrilateralToSquare(x0, y0, x1, y1, x2, y2, x3, y3);
-        squareToQuadrilateral(x0p, y0p, x1p, y1p, x2p, y2p, x3p, y3p));
+    PerspectiveTransform sToQ = squareToQuadrilateral(x0p, y0p, x1p, y1p, x2p, y2p, x3p, y3p);
+    PerspectiveTransform product = sToQ.times(qToS);
+    return product;
   }
 
   void transformPoints(float[] points) {
@@ -74,32 +76,31 @@ final class PerspectiveTransform {
     }
   }
 
-  private static PerspectiveTransform squareToQuadrilateral(float x0, float y0,
+  static PerspectiveTransform squareToQuadrilateral(float x0, float y0,
                                                             float x1, float y1,
                                                             float x2, float y2,
                                                             float x3, float y3) {
+    float dy2 = y3 - y2;
+    float dy3 = y0 - y1 + y2 - y3;
+    if (dy2 == 0.0f && dy3 == 0.0f) {
+      return new PerspectiveTransform(x1 - x0, x2 - x1, x0,
+                                      y1 - y0, y2 - y1, y0,
+                                      0.0f,    0.0f,    1.0f);
+    } else {
       float dx1 = x1 - x2;
       float dx2 = x3 - x2;
       float dx3 = x0 - x1 + x2 - x3;
       float dy1 = y1 - y2;
-    float dy2 = y3 - y2;
-    float dy3 = y0 - y1 + y2 - y3;
       float denominator = dx1*dy2 - dx2*dy1;
       float a13 = (dx3*dy2 - dx2*dy3) / denominator;
       float a23 = (dx1*dy3 - dx3*dy1) / denominator;
-
+      return new PerspectiveTransform(x1 - x0 + a13*x1, x3 - x0 + a23*x3, x0,
-	return new PerspectiveTransform(x1 - x0 + a13*x1,
+                                      y1 - y0 + a13*y1, y3 - y0 + a23*y3, y0,
-                                  x3 - x0 + a23*x3,
+                                      a13,              a23,              1.0f);
-                                  x0,
+    }
-                                  y1 - y0 + a13*y1,
-                                  y3 - y0 + a23*y3,
-                                  y0,
-                                  a13,
-                                  a23,
-                                  1.0f);
   }
 
-  private static PerspectiveTransform quadrilateralToSquare(float x0, float y0,
+  static PerspectiveTransform quadrilateralToSquare(float x0, float y0,
                                                             float x1, float y1,
                                                             float x2, float y2,
                                                             float x3, float y3) {
@@ -107,7 +108,7 @@ final class PerspectiveTransform {
     return squareToQuadrilateral(x0, y0, x1, y1, x2, y2, x3, y3).buildAdjoint();
   }
 
-  private PerspectiveTransform buildAdjoint() {
+  PerspectiveTransform buildAdjoint() {
     // Adjoint is the transpose of the cofactor matrix:
 	return new PerspectiveTransform(a22*a33 - a23*a32,
                                   a23*a31 - a21*a33,
@@ -120,16 +121,17 @@ final class PerspectiveTransform {
                                   a11*a22 - a12*a21);
   }
 
-  private PerspectiveTransform times(PerspectiveTransform other) {
+  PerspectiveTransform times(PerspectiveTransform other) {
     return new PerspectiveTransform(a11*other.a11 + a21*other.a12 + a31*other.a13,
-                                    a11*other.a12 + a12*other.a22 + a13*other.a32,
+                                    a11*other.a21 + a21*other.a22 + a31*other.a23,
-                                    a11*other.a13 + a12*other.a23 + a13*other.a33,
+                                    a11*other.a31 + a21*other.a32 + a31*other.a33,
-                                    a21*other.a11 + a22*other.a21 + a23*other.a31,
+                                    a12*other.a11 + a22*other.a12 + a32*other.a13,
-                                    a21*other.a12 + a22*other.a22 + a23*other.a32,
+                                    a12*other.a21 + a22*other.a22 + a32*other.a23,
-                                    a21*other.a13 + a22*other.a23 + a23*other.a33,
+                                    a12*other.a31 + a22*other.a32 + a32*other.a33,
-                                    a31*other.a11 + a32*other.a21 + a33*other.a31,
+                                    a13*other.a11 + a23*other.a12 + a33*other.a13,
-                                    a31*other.a12 + a32*other.a22 + a33*other.a33,
+                                    a13*other.a21 + a23*other.a22 + a33*other.a23,
-                                    a31*other.a13 + a32*other.a23 + a33*other.a33);
+                                    a13*other.a31 + a23*other.a32 + a33*other.a33);
+
   }
 
 }

core/test/src/com/google/zxing/qrcode/detector/PerspectiveTransformTestCase.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2007 Google Inc.
+ *
+ * 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 junit.framework.TestCase;
+
+/**
+ * @author srowen@google.com (Sean Owen)
+ */
+public final class PerspectiveTransformTestCase extends TestCase {
+
+  private static final float EPSILON = 0.0001f;
+
+  public void testSquareToQuadrilateral() {
+    PerspectiveTransform pt = PerspectiveTransform.squareToQuadrilateral(
+        2.0f, 3.0f, 10.0f, 4.0f, 16.0f, 15.0f, 4.0f, 9.0f);
+    assertPointEquals(2.0f, 3.0f, 0.0f, 0.0f, pt);
+    assertPointEquals(10.0f, 4.0f, 1.0f, 0.0f, pt);
+    assertPointEquals(4.0f, 9.0f, 0.0f, 1.0f, pt);
+    assertPointEquals(16.0f, 15.0f, 1.0f, 1.0f, pt);
+    assertPointEquals(6.535211f, 6.8873234f, 0.5f, 0.5f, pt);
+    assertPointEquals(48.0f, 42.42857f, 1.5f, 1.5f, pt);
+  }
+
+  public void testQuadrilateralToQuadrilateral() {
+    PerspectiveTransform pt = PerspectiveTransform.quadrilateralToQuadrilateral(
+        2.0f, 3.0f, 10.0f, 4.0f, 16.0f, 15.0f, 4.0f, 9.0f,
+        103.0f, 110.0f, 300.0f, 120.0f, 290.0f, 270.0f, 150.0f, 280.0f);
+    assertPointEquals(103.0f, 110.0f, 2.0f, 3.0f, pt);
+    assertPointEquals(300.0f, 120.0f, 10.0f, 4.0f, pt);
+    assertPointEquals(290.0f, 270.0f, 16.0f, 15.0f, pt);
+    assertPointEquals(150.0f, 280.0f, 4.0f, 9.0f, pt);
+    assertPointEquals(7.1516876f, -64.60185f, 0.5f, 0.5f, pt);
+    assertPointEquals(328.09116f, 334.16385f,50.0f, 50.0f, pt);
+  }
+
+  private static void assertPointEquals(float expectedX, float expectedY, float sourceX, float sourceY, PerspectiveTransform pt) {
+    float[] points = new float[] { sourceX, sourceY };
+    pt.transformPoints(points);
+    assertEquals(expectedX, points[0], EPSILON);
+    assertEquals(expectedY, points[1], EPSILON);
+  }
+
+}