convert VB to C#

Pilz.Drawing/BitmapExtensions.cs

@@ -0,0 +1,20 @@
+using global::System.Drawing;
+
+namespace Pilz.Drawing
+{
+    public static class BitmapExtensions
+    {
+        public static void InvertColors(this Bitmap bmp)
+        {
+            for (int y = 0, loopTo = bmp.Height - 1; y <= loopTo; y++)
+            {
+                for (int x = 0, loopTo1 = bmp.Width - 1; x <= loopTo1; x++)
+                {
+                    var inv = bmp.GetPixel(x, y);
+                    inv = Color.FromArgb(inv.A, byte.MaxValue - inv.R, byte.MaxValue - inv.G, byte.MaxValue - inv.B);
+                    bmp.SetPixel(x, y, inv);
+                }
+            }
+        }
+    }
+}