Unify and improve FromHex in ColorHelper.cs and ColorExtensions.cs

* Both now use ColorHelper.FromHex, rather than differing implementations * FromHex now accepts hex numbers with three and four digits matching HTML color codes, where "ABC" maps to "AABBCC" * Significant performance increase using bitshifts over string operations
craftworkgames · Nov 6, 2024 · 2127212 · 2127212
1 parent a0613cf
commit 2127212
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Showing 2 changed files with 41 additions and 13 deletions.
diff --git a/source/MonoGame.Extended/ColorExtensions.cs b/source/MonoGame.Extended/ColorExtensions.cs
@@ -11,11 +11,7 @@ public static class ColorExtensions
     {
         public static Color FromHex(string value)
         {
-            var r = int.Parse(value.Substring(1, 2), NumberStyles.HexNumber);
-            var g = int.Parse(value.Substring(3, 2), NumberStyles.HexNumber);
-            var b = int.Parse(value.Substring(5, 2), NumberStyles.HexNumber);
-            var a = value.Length > 7 ? int.Parse(value.Substring(7, 2), NumberStyles.HexNumber) : 255;
-            return new Color(r, g, b, a);
+            return ColorHelper.FromHex(value);
         }
 
         public static Color ToRgb(this HslColor c)

diff --git a/source/MonoGame.Extended/ColorHelper.cs b/source/MonoGame.Extended/ColorHelper.cs
@@ -45,13 +45,45 @@ public static Color FromHex(string value)
         {
             if (string.IsNullOrEmpty(value))
                 return Color.Transparent;
-            var startIndex = 0;
-            if (value.StartsWith("#"))
-                startIndex++;
-            var r = int.Parse(value.Substring(startIndex, 2), NumberStyles.HexNumber);
-            var g = int.Parse(value.Substring(startIndex + 2, 2), NumberStyles.HexNumber);
-            var b = int.Parse(value.Substring(startIndex + 4, 2), NumberStyles.HexNumber);
-            var a = value.Length > 6 + startIndex ? int.Parse(value.Substring(startIndex + 6, 2), NumberStyles.HexNumber) : 255;
+
+            if (value[0] == '#')
+                value = value.Substring(1);
+
+            int r, g, b, a;
+            uint hexInt = uint.Parse(value, System.Globalization.NumberStyles.HexNumber);
+            switch (value.Length)
+            {
+                case 6:
+                    r = (byte)((hexInt & 0x00FF0000) >> 16);
+                    g = (byte)((hexInt & 0x0000FF00) >> 8);
+                    b = (byte)(hexInt & 0x000000FF);
+                    a = 255;
+                    break;
+
+                case 8:
+                    r = (byte)((hexInt & 0xFF000000) >> 24);
+                    g = (byte)((hexInt & 0x00FF0000) >> 16);
+                    b = (byte)((hexInt & 0x0000FF00) >> 8);
+                    a = (byte)(hexInt & 0x000000FF);
+                    break;
+
+                case 3:
+                    r = (byte)(((hexInt & 0x00000F00) | (hexInt & 0x00000F00) << 4) >> 8);
+                    g = (byte)(((hexInt & 0x000000F0) | (hexInt & 0x000000F0) << 4) >> 4);
+                    b = (byte)((hexInt & 0x0000000F) | (hexInt & 0x0000000F) << 4);
+                    a = 255;
+                    break;
+
+                case 4:
+                    r = (byte)(((hexInt & 0x0000F000) | (hexInt & 0x0000F000) << 4) >> 12);
+                    g = (byte)(((hexInt & 0x00000F00) | (hexInt & 0x00000F00) << 4) >> 8);
+                    b = (byte)(((hexInt & 0x000000F0) | (hexInt & 0x000000F0) << 4) >> 4);
+                    a = (byte)((hexInt & 0x0000000F) | (hexInt & 0x0000000F) << 4);
+                    break;
+
+                default:
+                    throw new ArgumentException($"Malformed hexadecimal color: {value}");
+            }
 
             return new Color(r, g, b, a);
         }
@@ -80,4 +112,4 @@ public static Color FromName(string name)
             throw new InvalidOperationException($"{name} is not a valid color");
         }
     }
-}
+}