Merge pull request #170 from peters/master

.NET binding tweaks

src/bindings/csharp/openalpr-net/bitmapmat-net.h

@@ -65,7 +65,7 @@ namespace openalprnet {
 				channels = 4;
 				break;
 			default:
-				throw gcnew NotImplementedException();
+				throw gcnew NotSupportedException(bitmap->PixelFormat.ToString());
 			}
 
 			BitmapData^ bitmapData = bitmap->LockBits(

src/bindings/csharp/openalpr-net/helper-net.h

@@ -50,6 +50,11 @@ namespace openalprnet
 
 		static Bitmap^ MatToBitmap(cv::Mat mat)
 		{
+			if (mat.empty())
+			{
+				return nullptr;
+			}
+
 			const int width = mat.size().width;
 			const int height = mat.size().height;
 			const int channels = mat.channels();