Keeping it simple, ColorTransition will now just use sRGB premultiplied space

color interpolation.

src/Avalonia.Animation/ColorInterpolationMode.cs

@@ -1,33 +0,0 @@
-namespace Avalonia.Animation
-{
-    /// <summary>
-    /// Defines the intermediate color space
-    /// in which the color interpolation will be done.
-    /// </summary>
-    public enum ColorInterpolationMode
-    {
-        /// <summary>
-        /// Premultiply the alpha component and interpolate from RGB color space.
-        /// </summary>
-        PremultipliedRGB,
-
-        /// <summary>
-        /// Directly interpolate from RGB color space. 
-        /// Fastest but the least accurate, perception-wise.
-        /// </summary>
-        RGB,
-
-        /// <summary>
-        /// Converts RGB into HSV color space and interpolates. 
-        /// Slow but accurate, perception-wise.
-        /// </summary>
-        HSV,
-
-        /// <summary>
-        /// Converts RGB into HSV color space and interpolates. 
-        /// Slowest but the most accurate, perception-wise.
-        /// </summary>
-        LAB,
-
-    }
-}

src/Avalonia.Visuals/Animation/Transitions/ColorTransition.cs

@@ -11,73 +11,30 @@ namespace Avalonia.Animation.Transitions
 {
     /// <summary>
     /// Transition class that handles <see cref="AvaloniaProperty"/> with <see cref="SolidColorBrush"/> types.
-    /// TODO: Must be refactored to handle object creation.
+    /// TODO: Must be refactored to handle object creation every frame.
     /// </summary>  
     public class ColorTransition : Transition<SolidColorBrush>
     {
-
-        /// <summary>
-        /// Defines the <see cref="AnimationPlayState"/> property.
-        /// </summary>
-        public static readonly DirectProperty<ColorTransition, ColorInterpolationMode> InterpolationModeProperty =
-            AvaloniaProperty.RegisterDirect<ColorTransition, ColorInterpolationMode>(
-                nameof(InterpolationMode),
-                o => o.InterpolationMode,
-                (o, v) => o.InterpolationMode = v);
-
-        /// <summary>
-        /// Gets or sets the state of the animation for this
-        /// control.
-        /// </summary>
-        public ColorInterpolationMode InterpolationMode
-        {
-            get { return _interpolationMode; }
-            set { SetAndRaise(InterpolationModeProperty, ref _interpolationMode, value); }
-        }
-
-        private ColorInterpolationMode _interpolationMode;
-
         public override IObservable<SolidColorBrush> DoTransition(IObservable<double> progress, SolidColorBrush oldValue, SolidColorBrush newValue)
         {
-
             var oldColor = new Vector4(oldValue.Color.R, oldValue.Color.G, oldValue.Color.B, oldValue.Color.A);
             var newColor = new Vector4(newValue.Color.R, newValue.Color.G, newValue.Color.B, oldValue.Color.A);
             oldColor = oldColor / 255f;
             newColor = newColor / 255f;
             var deltaColor = newColor - oldColor;
+            var premultOV = new Vector4(oldColor.W, oldColor.W, oldColor.W, 1);
+            var premultNV = new Vector4(newColor.W, newColor.W, newColor.W, 1);
 
-            switch (InterpolationMode)
-            {
-                case ColorInterpolationMode.PremultipliedRGB:
-
-                    var premultOV = new Vector4(oldColor.W, oldColor.W, oldColor.W, 1);
-                    var premultNV = new Vector4(newColor.W, newColor.W, newColor.W, 1);
-
-                    oldColor *= premultOV;
-                    newColor *= premultNV;
-
-                    return progress
-                    .Select(p =>
-                    {
-                        var time = (float)Easing.Ease(p);
-                        var interpolatedColor = (deltaColor * time) + oldColor;
-                        return new SolidColorBrush(Color.FromVector4(interpolatedColor, true));
-                    });
-
-                case ColorInterpolationMode.RGB:
-                    return progress
-                    .Select(p =>
-                    {
-                        var time = (float)Easing.Ease(p);
-                        var interpolatedColor = (deltaColor * time) + oldColor;
-                        return new SolidColorBrush(Color.FromVector4(interpolatedColor, true));
-                    });
-                default:
-                    throw new NotImplementedException($"'{Enum.GetName(typeof(ColorInterpolationMode), InterpolationMode)}' color interpolation is not supported.");
-            }
-
+            oldColor *= premultOV;
+            newColor *= premultNV;
 
+            return progress
+            .Select(p =>
+            {
+                var time = (float)Easing.Ease(p);
+                var interpolatedColor = (deltaColor * time) + oldColor;
+                return new SolidColorBrush(Color.FromVector4(interpolatedColor, true));
+            });
         }
-
     }
 }