add function to scale (pen) line thickness.

DeathSocket/GridPainter.fs

@@ -15,7 +15,6 @@ namespace DeathSocket
 
         open Validation
         open ImageServices
-        open System
 
         /// <summary>
         /// Uses the information included in spec to create a gridded image.
@@ -30,7 +29,7 @@ namespace DeathSocket
         /// If the file the grid is being applied to cannot be found,
         /// a FileNotFoundException will be thrown.
         /// </exception>
-        /// <remarks
+        /// <remarks>
         /// Make sure the image, which is having the overlay added to it,
         /// is not in use or needed by another program/process.
         /// This is because it is locked whilst in this function.
@@ -54,7 +53,33 @@ namespace DeathSocket
                 with
                 | :? FileNotFoundException as ex ->
                     printfn "File could not be found at %s" ex.Message
-            } 
+            }
+
+        // NOT TESTED
+
+        /// <summary>
+        /// Takes an image and determines the current scale it is viewed at
+        /// (E.G. scaled preview in image viewer). The (pen) line thickness is
+        /// then updated to match this preview scale and can be used when
+        /// drawing a grid line on the scaled preview of the image.
+        /// </summary>
+        /// <param name="previewWidth">
+        /// The width of the image when previewed (I.E. in a GUI).
+        /// </param>
+        /// <param name="actualWidth">
+        /// The width of the actual image.
+        /// </param>
+        /// <param name="lineThickness">
+        /// The thickness of the pen used to draw the grid line.
+        /// </param>
+        /// <remarks>
+        /// You should find you only need this function when dealing with
+        /// previewing an image in a GUI. Another thing to note is the
+        /// SkiaSharp based functions already scale the grid lines for you. So,
+        /// you should not need to use this function when using them.
+        /// </remarks>
+        let scaleLineThickness (previewWidth: double) (actualWidth: double) (lineThickness: double) =
+            lineThickness / (previewWidth / actualWidth)
 
         // System.Drawing Functions
         // ========================================================================