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InkCanvasForClass/Helpers/ColorUtilities.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Media;
+
+namespace Ink_Canvas.Helpers
+{
+    public class ColorUtilities {
+
+        /// <summary>
+        /// 获取一个颜色的人眼感知亮度，并以 0~1 之间的小数表示。
+        /// </summary>
+        public static double GetGrayLevel(Color color) {
+            return (0.299 * color.R + 0.587 * color.G + 0.114 * color.B) / 255;
+        }
+
+        /// <summary>
+        /// 根据人眼感知亮度返回前景色到底是黑色还是白色
+        /// </summary>
+        /// <param name="grayLevel"><c>GetGrayLevel</c>返回的人眼感知亮度</param>
+        /// <returns>Color</returns>
+        public static Color GetReverseForegroundColor(double grayLevel) => grayLevel > 0.5 ? Colors.Black : Colors.White;
+    }
+}