add draw-default command-method.

Add function for building a default image spec in CLI.

SmoulderingBeachBallCLI/ConsoleCommands.fs

@@ -19,6 +19,16 @@
             |> makeImage
         *)
 
+        let ``draw-default`` imgWidth imgHeight =
+            try
+                buildDefaultSpec imgWidth imgHeight
+                |> makeImage
+                |> Async.RunSynchronously
+                showEndOfCommandMessage
+            with
+            | :? ArgumentException as ex -> ex.Message
+            | _ as ex -> ex.Message
+
         let ``draw-image`` imgWidth imgHeight mainColour path =
             try
                 buildBasicSpec imgWidth imgHeight mainColour path

SmoulderingBeachBallCLI/Validation.fs

@@ -30,14 +30,28 @@
                 (String.Concat("[ERROR] The colour specifed is invalid.\n",
                     "Please use the 'list-colours' command to see what you can use."))
 
+    let getDesktopPath =
+        Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
+
     let parsePath (path: string) =
         match path with
-        | path when ((path.ToLower()).Equals "desktop") -> 
-            Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
-        | path when ((path.ToLower()).Equals "d") -> 
-            Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
+        | path when ((path.ToLower()).Equals "desktop") -> getDesktopPath
+        | path when ((path.ToLower()).Equals "d") -> getDesktopPath
         | _ -> path
 
+    let buildDefaultSpec iWidth iHeight =
+        let oSpec =
+            { colour = Brushes.Black
+              overlayType = Full }
+        let spec =
+            { width = iWidth
+              height = iHeight
+              colour = Brushes.AntiqueWhite
+              filePath = getDesktopPath
+              overlay = Some oSpec
+            }
+        spec
+
     let buildBasicSpec iWidth iHeight mainColour path = 
         let spec =
             { width = iWidth;