From 7f06b18976a990c1fff47e5e88a041796ff66dbd Mon Sep 17 00:00:00 2001
From: srowen <srowen@59b500cc-1b3d-0410-9834-0bbf25fbcc57>
Date: Fri, 10 Jun 2011 08:43:38 +0000
Subject: [PATCH] Rationalize the black-run counting to avoid AIOOBE but also
 get the right answer still

git-svn-id: https://zxing.googlecode.com/svn/trunk@1820 59b500cc-1b3d-0410-9834-0bbf25fbcc57
---
 .../zxing/qrcode/detector/Detector.java       | 93 +++++++++----------
 1 file changed, 46 insertions(+), 47 deletions(-)

diff --git a/core/src/com/google/zxing/qrcode/detector/Detector.java b/core/src/com/google/zxing/qrcode/detector/Detector.java
index 724d39d59..070d85a83 100644
--- a/core/src/com/google/zxing/qrcode/detector/Detector.java
+++ b/core/src/com/google/zxing/qrcode/detector/Detector.java
@@ -256,33 +256,35 @@ public class Detector {
    */
   private float sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY) {
 
-   float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
+    float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
 
-   // Now count other way -- don't run off image though of course
-   float scale = 1.0f;
-   int otherToX = fromX - (toX - fromX);
-   if (otherToX < 0) {
-     scale = (float) fromX / (float) (fromX - otherToX);
-     otherToX = 0;
-   } else if (otherToX > image.getWidth()) {
-     scale = (float) (image.getWidth() - fromX) / (float) (otherToX - fromX);
-     otherToX = image.getWidth();
-   }
-   int otherToY = (int) (fromY - (toY - fromY) * scale);
+    // Now count other way -- don't run off image though of course
+    float scale = 1.0f;
+    int otherToX = fromX - (toX - fromX);
+    if (otherToX < 0) {
+      scale = (float) fromX / (float) (fromX - otherToX);
+      otherToX = 0;
+    } else if (otherToX >= image.getWidth()) {
+      scale = (float) (image.getWidth() - 1 - fromX) / (float) (otherToX - fromX);
+      otherToX = image.getWidth() - 1;
+    }
+    int otherToY = (int) (fromY - (toY - fromY) * scale);
 
-   scale = 1.0f;
-   if (otherToY < 0) {
-     scale = (float) fromY / (float) (fromY - otherToY);
-     otherToY = 0;
-   } else if (otherToY > image.getHeight()) {
-     scale = (float) (image.getHeight() - fromY) / (float) (otherToY - fromY);
-     otherToY = image.getHeight();
-   }
-   otherToX = (int) (fromX + (otherToX - fromX) * scale);
+    scale = 1.0f;
+    if (otherToY < 0) {
+      scale = (float) fromY / (float) (fromY - otherToY);
+      otherToY = 0;
+    } else if (otherToY >= image.getHeight()) {
+      scale = (float) (image.getHeight() - 1 - fromY) / (float) (otherToY - fromY);
+      otherToY = image.getHeight() - 1;
+    }
+    otherToX = (int) (fromX + (otherToX - fromX) * scale);
 
-   result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
-   return result;
- }
+    result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
+
+    // Middle pixel is double-counted this way; subtract 1
+    return result - 1.0f;
+  }
 
   /**
    * <p>This method traces a line from a point in the image, in the direction towards another point.
@@ -313,32 +315,22 @@ public class Detector {
 
     // In black pixels, looking for white, first or second time.
     int state = 0;
-    for (int x = fromX, y = fromY; x != toX; x += xstep) {
+    // Loop up until x == toX, but not beyond
+    int xLimit = toX + xstep;
+    for (int x = fromX, y = fromY; x != xLimit; x += xstep) {
       int realX = steep ? y : x;
       int realY = steep ? x : y;
 
-      // In white pixels, looking for black.
-      // FIXME(dswitkin): This method seems to assume square images, which can cause these calls to
-      // BitMatrix.get() to throw ArrayIndexOutOfBoundsException.
-      if (state == 1) {
-        if (image.get(realX, realY)) {
-          state++;
-        }
-      } else {
-        if (!image.get(realX, realY)) {
-          state++;
+      // Does current pixel mean we have moved white to black or vice versa?
+      if (!(state == 1 ^ image.get(realX, realY))) {
+        if (state == 2) {
+          int diffX = x - fromX;
+          int diffY = y - fromY;
+          return (float) Math.sqrt((double) (diffX * diffX + diffY * diffY));
         }
+        state++;
       }
 
-      // Found black, white, black, and stumbled back onto white, so we're done.
-      if (state == 3) {
-        int diffX = x - fromX;
-        int diffY = y - fromY;
-        if (xstep < 0) {
-            diffX++;
-        }
-        return (float) Math.sqrt((double) (diffX * diffX + diffY * diffY));
-      }
       error += dy;
       if (error > 0) {
         if (y == toY) {
@@ -348,9 +340,16 @@ public class Detector {
         error -= dx;
       }
     }
-    int diffX = toX - fromX;
-    int diffY = toY - fromY;
-    return (float) Math.sqrt((double) (diffX * diffX + diffY * diffY));
+    // Found black-white-black; give the benefit of the doubt that the next pixel outside the image
+    // is "white" so this last point at (toX+xStep,toY) is the right ending. This is really a
+    // small approximation; (toX+xStep,toY+yStep) might be really correct. Ignore this.
+    if (state == 2) {
+      int diffX = toX + xstep - fromX;
+      int diffY = toY - fromY;
+      return (float) Math.sqrt((double) (diffX * diffX + diffY * diffY));
+    }
+    // else we didn't find even black-white-black; no estimate is really possible
+    return Float.NaN;
   }
 
   /**