BufferedGraphics 类

  • 参考

定义

命名空间:
System.Drawing
程序集:
System.Drawing.Common.dll
程序集:
System.Drawing.dll

为双缓冲提供图形缓冲区。

public ref class BufferedGraphics sealed : IDisposable
public sealed class BufferedGraphics : IDisposable
type BufferedGraphics = class
    interface IDisposable
Public NotInheritable Class BufferedGraphics
Implements IDisposable
继承
Object
BufferedGraphics
实现
IDisposable

示例

下面的代码示例演示如何使用对象 BufferedGraphics 使用多种缓冲实现绘制图形。 单击窗体会启动并停止导致绘图更新的计时器。 使用绘图更新可以观察双缓冲的效果。 右键单击窗体将循环访问以下绘图模式：

在每个模式下，都会绘制用于标识当前模式的文本，并描述按下每个鼠标按钮时发生的行为。

#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>
#using <System.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Drawing;
using namespace System::Windows::Forms;

namespace BufferingExample
{
   public ref class BufferingExample: public Form
   {
   private:
      BufferedGraphicsContext^ context;
      BufferedGraphics^ grafx;
      Byte bufferingMode;
      array<String^>^bufferingModeStrings;
      System::Windows::Forms::Timer^ timer1;
      Byte count;

   public:
      BufferingExample()
         : Form()
      {
         array<String^>^tempStrings = {"Draw to Form without OptimizedDoubleBufferring control style","Draw to Form using OptimizedDoubleBuffering control style","Draw to HDC for form"};
         bufferingModeStrings = tempStrings;

         // Configure the Form for this example.
         this->Text = "User double buffering";
         this->MouseDown += gcnew MouseEventHandler( this, &BufferingExample::MouseDownHandler );
         this->Resize += gcnew EventHandler( this, &BufferingExample::OnResize );
         this->SetStyle( static_cast<ControlStyles>(ControlStyles::AllPaintingInWmPaint | ControlStyles::UserPaint), true );

         // Configure a timer to draw graphics updates.
         timer1 = gcnew System::Windows::Forms::Timer;
         timer1->Interval = 200;
         timer1->Tick += gcnew EventHandler( this, &BufferingExample::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 = System::Drawing::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(), 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 form's HDC.
         if ( bufferingMode == 2 )

         // Render the graphics buffer to the form's HDC.
         grafx->Render( Graphics::FromHwnd( this->Handle ) );
         // If in bufferingMode 0 or 1, draw in the paint method.
         else

         // If in bufferingMode 0 or 1, draw in the paint method.
         this->Refresh();
      }

      void OnResize( Object^ /*sender*/, EventArgs^ /*e*/ )
      {
         // Re-create the graphics buffer for a new window size.
         context->MaximumBuffer = System::Drawing::Size( this->Width + 1, this->Height + 1 );
         if ( grafx != nullptr )
         {
            delete grafx;
            grafx = nullptr;
         }

         grafx = context->Allocate( this->CreateGraphics(), Rectangle(0,0,this->Width,this->Height) );

         // Cause the background to be cleared and redraw.
         count = 6;
         DrawToBuffer( grafx->Graphics );
         this->Refresh();
      }

      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 = gcnew Random;
         for ( int i = 0; i < 20; i++ )
         {
            int px = rnd->Next( 20, this->Width - 40 );
            int py = rnd->Next( 20, this->Height - 40 );
            g->DrawEllipse( gcnew Pen( Color::FromArgb( rnd->Next( 0, 255 ), rnd->Next( 0, 255 ), rnd->Next( 0, 255 ) ), 1.0f ), px, py, px + rnd->Next( 0, this->Width - px - 20 ), py + rnd->Next( 0, this->Height - py - 20 ) );
         }

         // Draw information strings.
         g->DrawString( String::Format( "Buffering Mode: {0}", bufferingModeStrings[ bufferingMode ] ), gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 10 );
         g->DrawString( "Right-click to cycle buffering mode", gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 22 );
         g->DrawString( "Left-click to toggle timed display refresh", gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 34 );
      }

   protected:
      virtual void OnPaint( PaintEventArgs^ e ) override
      {
         grafx->Render( e->Graphics );
      }
   };
}

[STAThread]
int main()
{
   Application::Run( gcnew BufferingExample::BufferingExample );
}

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 form's HDC.
        if( bufferingMode == 2 )
                    // Render the graphics buffer to the form's 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; i<20; 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: "+bufferingModeStrings[bufferingMode], 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-click to toggle timed display refresh", new Font("Arial", 8), Brushes.White, 10, 34);
    }

    protected override void OnPaint(PaintEventArgs e)
        {
        grafx.Render(e.Graphics);
    }

        [STAThread]
        public static void Main(string[] args)
        {
        Application.Run(new BufferingExample());
        }
    }
}

Imports System.ComponentModel
Imports System.Drawing
Imports System.Windows.Forms

Public Class BufferingExample
    Inherits Form
    Private context As BufferedGraphicsContext
    Private grafx As BufferedGraphics
    
    Private bufferingMode As Byte
    Private bufferingModeStrings As String() = _
        {"Draw to Form without OptimizedDoubleBufferring control style", _
         "Draw to Form using OptimizedDoubleBuffering control style", _
         "Draw to HDC for form"}
    
    Private timer1 As System.Windows.Forms.Timer
    Private count As Byte    
    
    Public Sub New()
        ' Configure the Form for this example.
        Me.Text = "User double buffering"
        AddHandler Me.MouseDown, AddressOf Me.MouseDownHandler
        AddHandler Me.Resize, AddressOf Me.ResizeHandler
        Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.UserPaint, True)
        
        ' Configure a timer to draw graphics updates.
        timer1 = New System.Windows.Forms.Timer()
        timer1.Interval = 200
        AddHandler timer1.Tick, AddressOf Me.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(Me.Width + 1, Me.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(Me.CreateGraphics(), _
            New Rectangle(0, 0, Me.Width, Me.Height))
        
        ' Draw the first frame to the buffer.
        DrawToBuffer(grafx.Graphics)
    End Sub    
    
    Private Sub MouseDownHandler(sender As Object, e As MouseEventArgs)
        If e.Button = MouseButtons.Right Then
            ' Cycle the buffering mode.
            bufferingMode = bufferingMode+1
            If bufferingMode > 2 Then
                bufferingMode = 0
            End If 
            ' If the previous buffering mode used 
            ' the OptimizedDoubleBuffering ControlStyle,
            ' disable the control style.
            If bufferingMode = 1 Then
                Me.SetStyle(ControlStyles.OptimizedDoubleBuffer, True)
            End If 
            ' If the current buffering mode uses
            ' the OptimizedDoubleBuffering ControlStyle,
            ' enabke the control style.
            If bufferingMode = 2 Then
                Me.SetStyle(ControlStyles.OptimizedDoubleBuffer, False)
            End If 
            ' Cause the background to be cleared and redraw.
            count = 6
            DrawToBuffer(grafx.Graphics)
            Me.Refresh()
        Else
            ' Toggle whether the redraw timer is active.
            If timer1.Enabled Then
                timer1.Stop()
            Else
                timer1.Start()
            End If
        End If
    End Sub
     
    Private Sub OnTimer(sender As Object, e As EventArgs)
        ' Draw randomly positioned ellipses to the buffer.
        DrawToBuffer(grafx.Graphics)
        
        ' If in bufferingMode 2, draw to the form's HDC.
        If bufferingMode = 2 Then
            ' Render the graphics buffer to the form's HDC.
            grafx.Render(Graphics.FromHwnd(Me.Handle))
        ' If in bufferingMode 0 or 1, draw in the paint method.
        Else
            Me.Refresh()
        End If
    End Sub
     
    Private Sub ResizeHandler(sender As Object, e As EventArgs)
        ' Re-create the graphics buffer for a new window size.
        context.MaximumBuffer = New Size(Me.Width + 1, Me.Height + 1)
        If (grafx IsNot Nothing) Then
            grafx.Dispose()
            grafx = Nothing
        End If
        grafx = context.Allocate(Me.CreateGraphics(), New Rectangle(0, 0, Me.Width, Me.Height))
        
        ' Cause the background to be cleared and redraw.
        count = 6
        DrawToBuffer(grafx.Graphics)
        Me.Refresh()
    End Sub    
    
    Private Sub DrawToBuffer(g As Graphics)
        ' Clear the graphics buffer every five updates.
        count = count+1
        If count > 5 Then
            count = 0
            grafx.Graphics.FillRectangle(Brushes.Black, 0, 0, Me.Width, Me.Height)
        End If
        
        ' Draw randomly positioned and colored ellipses.
        Dim rnd As New Random()
        Dim i As Integer
        For i = 0 To 21
            Dim px As Integer = rnd.Next(20, Me.Width - 40)
            Dim py As Integer = rnd.Next(20, Me.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, Me.Width - px - 20), _
                py + rnd.Next(0, Me.Height - py - 20))
        Next i
        
        ' Draw information strings.
        g.DrawString("Buffering Mode: " + bufferingModeStrings(bufferingMode), _
            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-click to toggle timed display refresh", _
            New Font("Arial", 8), Brushes.White, 10, 34)
    End Sub    
    
    Protected Overrides Sub OnPaint(e As PaintEventArgs)
        grafx.Render(e.Graphics)
    End Sub   
    
    <STAThread()>  _
    Public Shared Sub Main(args() As String)
        Application.Run(New BufferingExample())
    End Sub

End Class

注解

该 BufferedGraphics 类允许你为图形实现自定义双缓冲。 它为图形缓冲区提供包装器，以及可用于写入缓冲区并将其内容呈现到输出设备的方法。

使用双缓冲的图形可以减少或消除由重绘显示图面引起的闪烁。 使用双缓冲时，更新后的图形首先绘制到内存中的缓冲区，然后此缓冲区的内容将快速写入部分或全部显示的图面。 这种相对短暂的显示图形覆盖通常会减少或消除在更新图形时有时发生的闪烁。

备注

在 .NET 6 及更高版本中，System.Drawing.Common包 （包括此类型）仅在 Windows操作系统上受支持。 在跨平台应用中使用此类型会导致编译时警告和运行时异常。 有关详细信息，请参阅仅支持System.Drawing.Common Windows。

备注

使用双缓冲的最简单方法是使用SetStyle该方法在控件上设置OptimizedDoubleBuffer控件样式标志。 设置控件的 OptimizedDoubleBuffer 标志会通过默认图形缓冲区重定向控件的所有绘制，而无需任何其他代码。 This flag is set to true by default.

该BufferedGraphics类没有公共构造函数，并且必须使用其Allocate方法为应用程序域创建BufferedGraphicsContext。 可以从静态BufferedGraphicsManager.Current属性检索BufferedGraphicsContext当前应用程序域。

该 Graphics 属性可用于绘制到图形缓冲区。 此属性提供对 Graphics 绘制到为此 BufferedGraphics 对象分配的图形缓冲区的对象的访问权限。

Render没有参数的方法将图形缓冲区的内容绘制到分配缓冲区时指定的图面。 此方法的其他重载 Render 允许指定 Graphics 指向要绘制图形缓冲区内容的设备上下文的对象或 IntPtr 对象。

有关绘制双缓冲图形的详细信息，请参阅 双缓冲图形。

属性

Graphics

获取输出到图形缓冲区的 Graphics 对象。

方法

Dispose()

释放由 BufferedGraphics 对象使用的所有资源。
Equals(Object)

确定指定对象是否等于当前对象。

(继承自 Object)
Finalize()

在垃圾回收将某一对象回收前允许该对象尝试释放资源并执行其他清理操作。
GetHashCode()

作为默认哈希函数。

(继承自 Object)
GetType()

获取当前实例的 Type。

(继承自 Object)
MemberwiseClone()

创建当前 Object 的浅表副本。

(继承自 Object)
Render()

将图形缓冲区的内容写入默认设备。
Render(Graphics)

将图形缓冲区的内容写入指定的 Graphics 对象。
Render(IntPtr)

将图形缓冲区的内容写入与指定的 IntPtr 句柄关联的设备上下文。
ToString()

返回表示当前对象的字符串。

(继承自 Object)

适用于

线程安全性

BufferedGraphics 类不是线程安全的。 从单独的线程访问图形缓冲区时，请务必使用线程访问控制机制来防止冲突。

另请参阅