diff --git a/SmoulderingBeachBall/ImageMaker.fs b/SmoulderingBeachBall/ImageMaker.fs
index 9f3e8df..7483178 100644
--- a/SmoulderingBeachBall/ImageMaker.fs
+++ b/SmoulderingBeachBall/ImageMaker.fs
@@ -5,6 +5,11 @@ module ImageMaker =
     open System
     open System.Drawing
     open System.IO
+    open System
+
+    type OverlaySpec = { colour: Brush}
+
+    type ImageSpec = { width: int; height: int; colour: Brush; filePath: string; overlay: Overlay }
 
     let private validateDimension dimension =
         match dimension with