For safety, make optimized round method consistent with Math.round for negative input too

core/src/main/java/com/google/zxing/common/detector/MathUtils.java

@@ -23,13 +23,15 @@ public final class MathUtils {
 
   /**
    * Ends up being a bit faster than {@link Math#round(float)}. This merely rounds its
-   * argument to the nearest int, where x.5 rounds up to x+1.
+   * argument to the nearest int, where x.5 rounds up to x+1. Semantics of this shortcut
+   * differ slightly from {@link Math#round(float)} in that half rounds down for negative
+   * values. -2.5 rounds to -3, not -2. For purposes here it makes no difference.
    *
    * @param d real value to round
    * @return nearest {@code int}
    */
   public static int round(float d) {
-    return (int) (d + 0.5f);
+    return (int) (d + (d < 0.0f ? -0.5f : 0.5f));
   }
 
   public static float distance(float aX, float aY, float bX, float bY) {

core/src/test/java/com/google/zxing/common/detector/MathUtilsTestCase.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2014 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.detector;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public final class MathUtilsTestCase extends Assert {
+
+  @Test
+  public void testRound() {
+    assertEquals(-1, MathUtils.round(-1.0f));
+    assertEquals(0, MathUtils.round(0.0f));
+    assertEquals(1, MathUtils.round(1.0f));
+
+    assertEquals(2, MathUtils.round(1.9f));
+    assertEquals(2, MathUtils.round(2.1f));
+
+    assertEquals(3, MathUtils.round(2.5f));
+
+    assertEquals(-2, MathUtils.round(-1.9f));
+    assertEquals(-2, MathUtils.round(-2.1f));
+
+    assertEquals(-3, MathUtils.round(-2.5f)); // This differs from Math.round()
+
+    assertEquals(Integer.MAX_VALUE, MathUtils.round(Integer.MAX_VALUE));
+    assertEquals(Integer.MIN_VALUE, MathUtils.round(Integer.MIN_VALUE));
+
+    assertEquals(Integer.MAX_VALUE, MathUtils.round(Float.POSITIVE_INFINITY));
+    assertEquals(Integer.MIN_VALUE, MathUtils.round(Float.NEGATIVE_INFINITY));
+
+    assertEquals(0, MathUtils.round(Float.NaN));
+  }
+
+}