Adds small exif library to read meta data from jpg's so we can attempt to read width/height from exif instead of loading the file into mem with GDI, makes for much faster and far less memory processing.U4-6246 Uploading specific images causes GDI+ Errors

src/Umbraco.Core/StringExtensions.cs

@@ -482,17 +482,27 @@ namespace Umbraco.Core
         /// <returns></returns>
         public static string ConvertToHex(this string input)
         {
-            if (String.IsNullOrEmpty(input)) return String.Empty;
+            if (string.IsNullOrEmpty(input)) return string.Empty;
 
             var sb = new StringBuilder(input.Length);
-            foreach (char c in input)
+            foreach (var c in input)
             {
-                int tmp = c;
                 sb.AppendFormat("{0:x2}", Convert.ToUInt32(c));
             }
             return sb.ToString();
         }
 
+        public static string DecodeFromHex(this string hexValue)
+        {
+            var strValue = "";
+            while (hexValue.Length > 0)
+            {
+                strValue += Convert.ToChar(Convert.ToUInt32(hexValue.Substring(0, 2), 16)).ToString();
+                hexValue = hexValue.Substring(2, hexValue.Length - 2);
+            }
+            return strValue;
+        }
+
         ///<summary>
         /// Encodes a string to a safe URL base64 string
         ///</summary>