fix getIOU bug (#2674)

* fix getIOU bug

* refactor Rectangle

---------

Co-authored-by: Frank Liu <frankfliu2000@gmail.com>

api/src/main/java/ai/djl/modality/cv/output/BoundingBox.java

@@ -41,7 +41,7 @@ public interface BoundingBox extends Serializable {
     Point getPoint();
 
     /**
-     * Gets the Intersection over Union (IoU) value between bounding boxes.
+     * Returns the Intersection over Union (IoU) value between bounding boxes.
      *
      * <p>Also known as <a href="https://en.wikipedia.org/wiki/Jaccard_index">Jaccard index</a>
      *

api/src/main/java/ai/djl/modality/cv/output/Rectangle.java

@@ -86,15 +86,26 @@ public Point getPoint() {
     /** {@inheritDoc} */
     @Override
     public double getIoU(BoundingBox box) {
-        Rectangle rec = (Rectangle) box;
-        // caculate intesection lrtb
-        double left = Math.max(getX(), rec.getX());
-        double top = Math.max(getY(), rec.getY());
-        double right = Math.min(getX() + getWidth(), rec.getX() + rec.getWidth());
-        double bottom = Math.min(getY() + getHeight(), rec.getY() + rec.getHeight());
-        double intersection = (right - left) * (bottom - top);
-        return intersection
-                / (getWidth() * getHeight() + rec.getWidth() * rec.getHeight() - intersection);
+        Rectangle rect = box.getBounds();
+
+        // computing area of each rectangles
+        double s1 = (width + 1) * (height + 1);
+        double s2 = (rect.getWidth() + 1) * (rect.getHeight() + 1);
+        double sumArea = s1 + s2;
+
+        // find each edge of intersect rectangle
+        double left = Math.max(getX(), rect.getX());
+        double top = Math.max(getY(), rect.getY());
+        double right = Math.min(getX() + getWidth(), rect.getX() + rect.getWidth());
+        double bottom = Math.min(getY() + getHeight(), rect.getY() + rect.getHeight());
+
+        // judge if there is a intersect
+        if (left > right || top > bottom) {
+            return 0.0;
+        }
+
+        double intersect = (right - left + 1) * (bottom - top + 1);
+        return intersect / (sumArea - intersect);
     }
 
     /**

api/src/test/java/ai/djl/modality/cv/output/RectangleTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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 ai.djl.modality.cv.output;
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+public class RectangleTest {
+
+    @Test
+    public void testIoU() {
+        BoundingBox box = new Rectangle(1, 3, 4, 5);
+        Rectangle rect = new Rectangle(1, 2, 3, 4);
+        double iou = box.getIoU(rect);
+        Assert.assertEquals(iou, 0.47058823529411764, 0.00001);
+
+        rect = new Rectangle(6, 2, 3, 4);
+        iou = box.getIoU(rect);
+        Assert.assertEquals(iou, 0);
+    }
+}

api/src/test/java/ai/djl/modality/cv/output/package-info.java

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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.
+ */
+/** Contains tests for {@link ai.djl.modality.cv.output}. */
+package ai.djl.modality.cv.output;