Fixes the zoom calculation

Former-commit-id: 631be0d9a0d36d2edcbd06578724f275d404127f
Former-commit-id: 41ac4115350de23c773d8490d3fea04650cf578d

src/ImageProcessor.UnitTests/Imaging/RotationUnitTests.cs

@@ -23,6 +23,9 @@
         [TestCase(100, 100, 45, 1.41f)]
         [TestCase(100, 100, 15, 1.22f)]
         [TestCase(100, 200, 45, 2.12f)]
+        [TestCase(200, 100, 45, 2.12f)]
+        [TestCase(600, 450, 20, 1.39f)]
+        [TestCase(600, 450, 45, 1.64f)]
         public void RotationZoomIsCalculated(int imageWidth, int imageHeight, float angle, float expected)
         {
             float result = Rotation.ZoomAfterRotation(imageWidth, imageHeight, angle);

src/ImageProcessor/Imaging/Rotation.cs

@@ -56,7 +56,7 @@
             double widthRotated = (imageWidth * radiansCos) + (imageHeight * radiansSin);
             double heightRotated = (imageWidth * radiansSin) + (imageHeight * radiansCos);
 
-            return (float)(Math.Max(widthRotated, heightRotated) / 100);
+            return (float)Math.Max(widthRotated / imageWidth, heightRotated / imageHeight);
         }
     }
 }