Applications=Code+Markup 读书笔记之二 基本画刷

二 基本画刷
1 Color (在System.Window.Media下) 除R、G、B外还有一个属性A 控制颜色的“不透明”程度，0-255，越小越透明。
  Color clr = Color.FromRgb(r,g,b) //A值是255
  Color clr = Color.FromArgb(a,r,g,b)
  sRGB:电脑显示器或数码相机上适用的颜色空间
  scRGB:ScR、ScG、ScB为单精度的浮点数，可以小于0或大于1，以容纳超出显示器和sRGB数字范围的颜色。
2 Brush
  OBject
    DispatcherObject
      Freezable
       Animatable
         Brush(抽象类)
           GradientBrush
             LinearGradientBrush
             RadialGradientBrush
           SolidColorBrush
           TileBrush
             DrawingBrush
             ImageBrush
             VisualBrush
   Color clr=Color.FromRgb(0,255,255);
   SolidColorBrush brush = new SolidColorBrush(clr);
   Background = bush
  
   利用Brushes所取得的SolidColorBrush对象处于冻结(frozen)状态，不能再被改变。将对象冻结可以提高效率，冻结的Freezable对象可以在不同的线程之间共享。
   从SystemColors返回的画刷对象都是冻结的，程序可以动态改变下面的画刷
   Brush brush = new SystemColorBursh(SystemColors.windowcolor);
   但不能改变下面的画刷
   Brush brush = SystemColors.windowBrush;

3 渐变画刷 LinearGradientBrush，需要两个点，两个颜色值
  LinearGradientBrush brush = new LinearGradientBrush(Colors.Red,Colors.Blue,new Point(0,0),new Point(1,1)
  Background = brush;

 

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace Petzold.AdjustTheGradient
{
    class AdjustTheGradient: Window
    {
        LinearGradientBrush brush;

        [STAThread]
        public static void Main()
        {
            Application app = new Application();
            app.Run(new AdjustTheGradient());
        }
        public AdjustTheGradient()
        {
            Title = "Adjust the Gradient";
            SizeChanged += WindowOnSizeChanged;

            brush = new LinearGradientBrush(Colors.Red, Colors.Blue, 0);
            brush.MappingMode = BrushMappingMode.Absolute;
            Background = brush;
        }
        void WindowOnSizeChanged(object sender, SizeChangedEventArgs args)
        {
            double width = ActualWidth
                - 2 * SystemParameters.ResizeFrameVerticalBorderWidth;
            double height = ActualHeight
                - 2 * SystemParameters.ResizeFrameHorizontalBorderHeight
                - SystemParameters.CaptionHeight;

            Point ptCenter = new Point(width / 2, height / 2);
            Vector vectDiag = new Vector(width, -height);
            Vector vectPerp = new Vector(vectDiag.Y, -vectDiag.X);

            vectPerp.Normalize();
            vectPerp *= width * height / vectDiag.Length;

            brush.StartPoint = ptCenter + vectPerp;
            brush.EndPoint = ptCenter - vectPerp;
        }
    }
}

 

LinearGradientBrush 使用GradientBrush定义的GradientStops Property，渐变颜色可以有多个，典型的应用如：可以实现七彩虹。

 

 namespace Petzold.FollowTheRainbow
{
    class FollowTheRainbow: Window
    {
        [STAThread]
        public static void Main()
        {
            Application app = new Application();
            app.Run(new FollowTheRainbow());
        }
        public FollowTheRainbow()
        {
            Title = "Follow the Rainbow";

            LinearGradientBrush brush = new LinearGradientBrush();
            brush.StartPoint = new Point(0, 0);
            brush.EndPoint = new Point(1, 0);
            Background = brush;

            // Rainbow mnemonic is the name Roy G. Biv.
            brush.GradientStops.Add(new GradientStop(Colors.Red, 0));
            brush.GradientStops.Add(new GradientStop(Colors.Orange, .17));
            brush.GradientStops.Add(new GradientStop(Colors.Yellow, .33));
            brush.GradientStops.Add(new GradientStop(Colors.Green, .5));
            brush.GradientStops.Add(new GradientStop(Colors.Blue, .67));
            brush.GradientStops.Add(new GradientStop(Colors.Indigo, .84));
            brush.GradientStops.Add(new GradientStop(Colors.Violet, 1));
        }
    }
}

 

 
4 渐变画刷 RadialGradientBrush 椭圆画刷，有Center,RadiusX,RadiusY等属性

5 BorderBrush 注意是Window的Brush Property，在客户区绘制边框
  BorderBrush = new GradientBrush(Colors.Red,Colors.Blue,new Point(1,0),new Point(1,1));