diff --git a/DeathSocket/Domain.fs b/DeathSocket/Domain.fs
index 834f72c..a6d9276 100644
--- a/DeathSocket/Domain.fs
+++ b/DeathSocket/Domain.fs
@@ -167,4 +167,8 @@
             /// Denotes an image created using SkiaSharp
             | SkiaSharp of string
             /// Denotes an image created using System.Drawing
-            | SystemDrawing of string
\ No newline at end of file
+            | SystemDrawing of string
+
+        type internal longestDimension =
+            | Width
+            | Height
\ No newline at end of file
diff --git a/DeathSocket/GridPainter.fs b/DeathSocket/GridPainter.fs
index 59a68b2..f109803 100644
--- a/DeathSocket/GridPainter.fs
+++ b/DeathSocket/GridPainter.fs
@@ -55,6 +55,7 @@ namespace DeathSocket
                     printfn "File could not be found at %s" ex.Message
             }
 
+        // NOT TESTED.
         /// <summary>
         /// Determines the current scale an image is viewed at (E.G. scaled
         /// preview in image viewer). The (pen) line thickness is then updated
@@ -76,8 +77,11 @@ namespace DeathSocket
         /// 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 (previewDimension: double) (actualDimension: double) (lineThickness: double) =
-            setLineThickness previewDimension actualDimension lineThickness
+        let scaleLineThickness (previewDimensions: int * int) (actualDimensions: int * int) (lineThickness: double) =
+            validateDimensions previewDimensions |> ignore
+            validateDimensions actualDimensions |> ignore
+            validateLineThickness |> ignore
+            adjustLineThickness previewDimensions actualDimensions lineThickness
 
         /// <summary>
         /// Reads an (jpg or png) image and return its width and height as a
diff --git a/DeathSocket/ImageServices.fs b/DeathSocket/ImageServices.fs
index 2033b4d..dd5c295 100644
--- a/DeathSocket/ImageServices.fs
+++ b/DeathSocket/ImageServices.fs
@@ -1,12 +1,13 @@
 module internal ImageServices
 
+    open System
     open System.IO
     open System.Drawing
     open System.Drawing.Imaging
     open DeathSocket
+    open Validation
     open ColourServices
     open SkiaSharp
-    open System
 
     (* Note on the Use of Repeated Code
     ===========================================================================
@@ -20,10 +21,24 @@
     lurking in an end users RAM can grind their computer to a halt. On top of
     that, they have no means to make alterations to the code. *)
 
-    let setLineThickness pDimension aDimension lineWidth =
-        if (pDimension <= 0.0 || aDimension <= 0.0 || lineWidth <= 0.0) then
-            raise (new DivideByZeroException ("[ERROR] The images height and width must be greater than 0."))
-        else lineWidth / (pDimension / aDimension)
+    let determineImageScale pDimension aDimension =
+        (double aDimension) / (double pDimension)
+
+    let determineLineScale (lineWidth: double) (scale: double) =
+        lineWidth / scale
+
+    let adjustLineThickness pDimensions aDimensions lineWidth =
+        match (validateLongestDimension pDimensions aDimensions) with
+        | Width ->
+            let thickness =
+                determineImageScale (fst pDimensions) (fst aDimensions)
+                |> determineLineScale lineWidth
+            thickness
+        | Height ->
+            let thickness =
+                determineImageScale (snd pDimensions) (snd aDimensions)
+                |> determineLineScale lineWidth
+            thickness
 
     (* SkiaSharp Functions
     ======================================================================== *)
diff --git a/DeathSocket/Validation.fs b/DeathSocket/Validation.fs
index edc208a..8e3f707 100644
--- a/DeathSocket/Validation.fs
+++ b/DeathSocket/Validation.fs
@@ -1,11 +1,12 @@
 module internal Validation
 
     open System.IO
+    open DeathSocket
 
     let validateFilePath path =
         match File.Exists path with
         | true -> ()
-        | false -> raise (new FileNotFoundException (path + " could not be found."))
+        | false -> raise (new FileNotFoundException ("No file found at " + path))
 
     let validateSaveFileType file =
         match Path.GetExtension file with
@@ -17,4 +18,22 @@
 
     let validateIO iPath oPath =
         validateFilePath iPath
-        validateSaveFileType oPath
\ No newline at end of file
+        validateSaveFileType oPath
+
+    let validateDimensions dimensions =
+        match dimensions with
+        | (0, _) -> invalidArg "Width" "Width must be greater than 0."
+        | (_, 0) -> invalidArg "Height" "Height must be greater than 0."
+        | (_, _) -> ()
+
+    let validateLineThickness thickness =
+        match thickness with
+        | thickness when thickness <= 0.0 -> invalidArg "LineThickness" "LineThickness must be greater than 0."
+        | _ -> ()
+
+    let validateLongestDimension pDims aDims =
+        let width = (fst pDims) - (fst aDims)
+        let height = (snd pDims) - (snd aDims)
+        match width >= height with
+        | true -> Width
+        | false -> Height
\ No newline at end of file