Improve RGB Min Max evaluation performance by using 2 or 3 comparison… (#50622)

Author: L2

src/libraries/System.Drawing.Primitives/src/System/Drawing/Color.cs

@@ -487,12 +487,34 @@ private void GetRgbValues(out int r, out int g, out int b)
             b = (int)(value & ARGBBlueMask) >> ARGBBlueShift;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void MinMaxRgb(out int min, out int max, int r, int g, int b)
+        {
+            if (r > g)
+            {
+                max = r;
+                min = g;
+            }
+            else
+            {
+                max = g;
+                min = r;
+            }
+            if (b > max)
+            {
+                max = b;
+            }
+            else if (b < min)
+            {
+                min = b;
+            }
+        }
+
         public float GetBrightness()
         {
             GetRgbValues(out int r, out int g, out int b);
 
-            int min = Math.Min(Math.Min(r, g), b);
-            int max = Math.Max(Math.Max(r, g), b);
+            MinMaxRgb(out int min, out int max, r, g, b);
 
             return (max + min) / (byte.MaxValue * 2f);
         }
@@ -504,8 +526,7 @@ public float GetHue()
             if (r == g && g == b)
                 return 0f;
 
-            int min = Math.Min(Math.Min(r, g), b);
-            int max = Math.Max(Math.Max(r, g), b);
+            MinMaxRgb(out int min, out int max, r, g, b);
 
             float delta = max - min;
             float hue;
@@ -531,8 +552,7 @@ public float GetSaturation()
             if (r == g && g == b)
                 return 0f;
 
-            int min = Math.Min(Math.Min(r, g), b);
-            int max = Math.Max(Math.Max(r, g), b);
+            MinMaxRgb(out int min, out int max, r, g, b);
 
             int div = max + min;
             if (div > byte.MaxValue)

src/libraries/System.Drawing.Primitives/tests/ColorTests.cs

@@ -390,6 +390,12 @@ private void CheckRed(Color color)
         [InlineData(51, 255, 51, 0.6f)]
         [InlineData(51, 51, 255, 0.6f)]
         [InlineData(51, 51, 51, 0.2f)]
+        [InlineData(0, 51, 255, 0.5f)]
+        [InlineData(51, 255, 0, 0.5f)]
+        [InlineData(0, 255, 51, 0.5f)]
+        [InlineData(255, 0, 51, 0.5f)]
+        [InlineData(51, 0, 255, 0.5f)]
+        [InlineData(255, 51, 0, 0.5f)]
         public void GetBrightness(int r, int g, int b, float expected)
         {
             Assert.Equal(expected, Color.FromArgb(r, g, b).GetBrightness());