Add IColorPalette

src/Avalonia.Controls.ColorPicker/ColorPalette/IColorPalette.cs

@@ -0,0 +1,38 @@
+using Avalonia.Media;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Interface to define a color palette.
+    /// </summary>
+    public interface IColorPalette
+    {
+        /// <summary>
+        /// Gets the total number of colors in this palette.
+        /// A color is not necessarily a single value and may be composed of several shades.
+        /// </summary>
+        /// <remarks>
+        /// Represents total columns in a table.
+        /// </remarks>
+        int ColorCount { get; }
+
+        /// <summary>
+        /// Gets the total number of shades for each color in this palette.
+        /// Shades are usually a variation of the color lightening or darkening it.
+        /// </summary>
+        /// <remarks>
+        /// Represents total rows in a table.
+        /// </remarks>
+        int ShadeCount { get; }
+
+        /// <summary>
+        /// Gets a color in the palette by index.
+        /// </summary>
+        /// <param name="colorIndex">The index of the color in the palette.
+        /// The index must be between zero and <see cref="ColorCount"/>.</param>
+        /// <param name="shadeIndex">The index of the color shade in the palette.
+        /// The index must be between zero and <see cref="ShadeCount"/>.</param>
+        /// <returns>The color at the specified index or an exception.</returns>
+        Color GetColor(int colorIndex, int shadeIndex);
+    }
+}