update the drawGrid function to work with images with indexed pixels.

The change, also, stop images with no indexed pixels from being cropped.

DeathSocket/ImageServices.fs

@@ -18,16 +18,17 @@
                Point ((interval * point), height)|]|]
 
     let drawGrid spec =
-        let img = Bitmap.FromFile spec.originalPath
-        let graphics = Graphics.FromImage(img)
-        let pen = new Pen (spec.colour, width = spec.penWidth)
+        // The temp. file is used as a way to convert images with index pixels.
+        use original = Bitmap.FromFile spec.originalPath
+        use temp = new Bitmap(original)
+        use clone = temp.Clone(new Rectangle(0, 0, temp.Width, temp.Height), PixelFormat.Format32bppArgb)
+        use graphics = Graphics.FromImage(clone)
+        use pen = new Pen (spec.colour, width = spec.penWidth)
+        graphics.DrawImage(original,new Rectangle(0, 0, clone.Width, clone.Height))
         let horizontalLines =
-            createHorizontalLines (img.Size.Width) (img.Size.Height) (spec.rows)
+            createHorizontalLines (clone.Size.Width) (clone.Size.Height) (spec.rows)
         let verticalLines =
-            createVerticalLines (img.Size.Width) (img.Size.Height) (spec.columns)
+            createVerticalLines (clone.Size.Width) (clone.Size.Height) (spec.columns)
         for line in horizontalLines do graphics.DrawLines (pen, line)
         for line in verticalLines do graphics.DrawLines (pen, line)
-        img.Save (spec.savePath)
-        img.Dispose()
-        graphics.Dispose()
-        pen.Dispose()
+        clone.Save (spec.savePath)