C#使用BufferedGraphics实现GDI+双缓冲绘图.doc

使用双缓冲的图形可以减少或消除重绘显示图面时产生的闪烁。使用双缓冲时，更新的图形首先被绘制到内存的缓冲区中，然后，此缓冲区的内容被迅速写入某些或所有显示的图面中。显示图形的重写相对简短，这通常可以减少或消除有时在更新图形时出现的闪烁。 使用C# GDI+绘图，实现双缓冲绘图有几种方法，在这篇文章中，将介绍其中的一种使用BufferedGraphics实现GDI+双缓冲绘图。 下面的代码示例演示如何使用BufferedGraphics对象绘制以下图形，这些图形使用几种类型的缓冲实现。单击窗体将启动或停止一个计时器，该计时器将引起绘制更新。绘制更新使您可以观察双缓冲的效果。右击窗体将循环使用下列绘制模式： 对于Form，直接绘制到Handle。 对使用OptimizedDoubleBuffer控件样式的OnPaint方法进行重写，以进行绘制 对于不使用OptimizedDoubleBuffer控件样式的窗体方法，重写OnPaint方法以进行绘制。 在每种模式下都将绘制文本，以标识当前模式并描述按下每个鼠标按钮时发生的行为。using System;using System.ComponentModel;using System.Drawing;using System.Windows.Forms;namespace BufferingExample public class BufferingExample : Form private BufferedGraphicsContext context; private BufferedGraphics grafx; private byte bufferingMode; private string bufferingModeStrings = Draw to Form without OptimizedDoubleBufferring control style, Draw to Form using OptimizedDoubleBuffering control style, Draw to HDC for form ; private System.Windows.Forms.Timer timer1; private byte count; public BufferingExample() : base() / Configure the Form for this example. this.Text = User double buffering; this.MouseDown += new MouseEventHandler(this.MouseDownHandler); this.Resize += new EventHandler(this.OnResize); this.SetStyle( ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true ); / Configure a timer to draw graphics updates. timer1 = new System.Windows.Forms.Timer(); timer1.Interval = 200; timer1.Tick += new EventHandler(this.OnTimer); bufferingMode = 2; count = 0; / Retrieves the BufferedGraphicsContext for the / current application domain. context = BufferedGraphicsManager.Current; / Sets the maximum size for the primary graphics buffer / of the buffered graphics context for the application / domain. Any allocation requests for a buffer larger / than this will create a temporary buffered graphics / context to host the graphics buffer. context.MaximumBuffer = new Size(this.Width+1, this.Height+1); / Allocates a graphics buffer the size of this form / using the pixel format of the Graphics created by / the Form.CreateGraphics() method, which returns a / Graphics object that matches the pixel format of the form. grafx = context.Allocate(this.CreateGraphics(), new Rectangle( 0, 0, this.Width, this.Height ); / Draw the first frame to the buffer. DrawToBuffer(grafx.Graphics); private void MouseDownHandler(object sender, MouseEventArgs e) if( e.Button = MouseButtons.Right ) / Cycle the buffering mode. if( +bufferingMode 2 ) bufferingMode = 0; / If the previous buffering mode used / the OptimizedDoubleBuffering ControlStyle, / disable the control style. if( bufferingMode = 1 ) this.SetStyle( ControlStyles.OptimizedDoubleBuffer, true ); / If the current buffering mode uses / the OptimizedDoubleBuffering ControlStyle, / enabke the control style. if( bufferingMode = 2 ) this.SetStyle( ControlStyles.OptimizedDoubleBuffer, false ); / Cause the background to be cleared and redraw. count = 6; DrawToBuffer(grafx.Graphics); this.Refresh(); else / Toggle whether the redraw timer is active. if( timer1.Enabled ) timer1.Stop(); else timer1.Start(); private void OnTimer(object sender, EventArgs e) / Draw randomly positioned ellipses to the buffer. DrawToBuffer(grafx.Graphics); / If in bufferingMode 2, draw to the forms HDC. if( bufferingMode = 2 ) / Render the graphics buffer to the forms HDC. grafx.Render(Graphics.FromHwnd(this.Handle); / If in bufferingMode 0 or 1, draw in the paint method. else this.Refresh(); private void OnResize(object sender, EventArgs e) / Re-create the graphics buffer for a new window size. context.MaximumBuffer = new Size(this.Width+1, this.Height+1); if( grafx != null ) grafx.Dispose(); grafx = null; grafx = context.Allocate(this.CreateGraphics(), new Rectangle( 0, 0, this.Width, this.Height ); / Cause the background to be cleared and redraw. count = 6; DrawToBuffer(grafx.Graphics); this.Refresh(); private void DrawToBuffer(Graphics g) / Clear the graphics buffer every five updates. if( +count 5 ) count = 0; grafx.Graphics.FillRectangle(Brushes.Black, 0, 0, this.Width, this.Height); / Draw randomly positioned and colored ellipses. Random rnd = new Random(); for( int i=0; i20; i+ ) int px = rnd.Next(20,this.Width-40); int py = rnd.Next(20,this.Height-40); g.DrawEllipse(new Pen(Color.FromArgb(rnd.Next(0, 255), rnd.Next(0,255), rnd.Next(0,255), 1), px, py, px+rnd.Next(0, this.Width-px-20), py+rnd.Next(0, this.Height-py-20); / Draw information strings. g.DrawString(Buffering Mode: +bufferingModeStringsbufferingMode, new Font(Arial, 8), Brushes.White, 10, 10); g.DrawString(Right-click to cycle buffering mode, new Font(Arial, 8), Brushes.White, 10, 22); g.DrawString(Left-cli