如何实现像ACDSEE,PHOTOSHOP那样拖动图象时的平滑滚动？

Question

http://www.codeproject.com/cs/media/flickerFreeDrawing.asp

Answer 1

http://www.codeproject.com/cs/media/flickerFreeDrawing.asp

Answer 2

如下是我以前自己写的：
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Threading;namespace MyAlbum
{
/// <summary>
/// Summary description for frmFullScreen.
/// </summary>
public class frmFullScreen : System.Windows.Forms.Form
{
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null; private Bitmap bitCurrent=null;
private Point ptCurrent;
private Point ptStart;
private Size sShowing;
private Point ptMouseDown; private const int MOVESIZE=20;
private Cursor curApp=null;
private Cursor curImage=null; public frmFullScreen(ref Bitmap bitShow)
{
//
// Required for Windows Form Designer support
//
InitializeComponent(); //
// TODO: Add any constructor code after InitializeComponent call
//
bitCurrent=bitShow; ptStart=new Point(0,0);
sShowing=new Size(0,0);
if(bitCurrent.Width<Screen.PrimaryScreen.Bounds.Width)
{
ptStart.X=(Screen.PrimaryScreen.Bounds.Width-bitCurrent.Width)/2;
sShowing.Width=bitCurrent.Width;
}
else
{
ptStart.X=0;
sShowing.Width=Screen.PrimaryScreen.Bounds.Width;
} if(bitCurrent.Height<Screen.PrimaryScreen.Bounds.Height)
{
ptStart.Y=(Screen.PrimaryScreen.Bounds.Height-bitCurrent.Height)/2;
sShowing.Height=bitCurrent.Height;
}
else
{
ptStart.Y=0;
sShowing.Height=Screen.PrimaryScreen.Bounds.Height;
} ptCurrent=new Point(0,0);
ptMouseDown=new Point(0,0);
} /// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if(components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
} private void frmFullScreen_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
if(e.KeyCode==Keys.Escape)
this.Close(); if(e.KeyCode==Keys.Up)
{
if(sShowing.Height<Screen.PrimaryScreen.Bounds.Height)
return;
else if(ptCurrent.Y==0)
return;
                
if((ptCurrent.Y-MOVESIZE)<0)
ptCurrent.Y=0;
else
ptCurrent.Y=ptCurrent.Y-MOVESIZE; //Then redraw
this.OnPaint(new PaintEventArgs(this.CreateGraphics(),this.Bounds));
} if(e.KeyCode==Keys.Down)
{
if(sShowing.Height<Screen.PrimaryScreen.Bounds.Height)
return;
else if((ptCurrent.Y+sShowing.Height)==bitCurrent.Height)
return; if((ptCurrent.Y+MOVESIZE+sShowing.Height)<bitCurrent.Height)
ptCurrent.Y+=MOVESIZE;
else
ptCurrent.Y=bitCurrent.Height-sShowing.Height; //Then redraw
this.OnPaint(new PaintEventArgs(this.CreateGraphics(),this.Bounds));
} if(e.KeyCode==Keys.Left)
{
if(sShowing.Width<Screen.PrimaryScreen.Bounds.Width)
return;
else if(ptCurrent.X==0)
return;
                
if((ptCurrent.X-MOVESIZE)<0)
ptCurrent.X=0;
else
ptCurrent.X-=MOVESIZE; //Then redraw
this.OnPaint(new PaintEventArgs(this.CreateGraphics(),this.Bounds));
} if(e.KeyCode==Keys.Right)
{
if(sShowing.Width<Screen.PrimaryScreen.Bounds.Width)
return;
else if((ptCurrent.X+sShowing.Width)==bitCurrent.Width)
return; if((ptCurrent.X+MOVESIZE+sShowing.Width)<bitCurrent.Width)
ptCurrent.X+=MOVESIZE;
else
ptCurrent.X=bitCurrent.Width-sShowing.Width; //Then redraw
this.OnPaint(new PaintEventArgs(this.CreateGraphics(),this.Bounds));
}
} protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.DrawImage(bitCurrent,
new Rectangle(ptStart,sShowing),
new Rectangle(ptCurrent,sShowing),
GraphicsUnit.Pixel);
} private void frmFullScreen_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
if((e.X>ptStart.X)&&(e.Y>ptStart.Y)&&
(e.X<(ptStart.X+sShowing.Width))&&(e.Y<(ptStart.Y+sShowing.Height)))
{
this.Cursor=curImage;
}
else
{
this.Cursor=curApp;
return;
} if(e.Button==MouseButtons.Left)
{
bool blnXChanged=false;
bool blnYChanged=false;
if(e.Y>ptMouseDown.Y)
{
if((sShowing.Height>=Screen.PrimaryScreen.Bounds.Height)
&&(ptCurrent.Y!=0))
{
blnYChanged=true;
if((ptCurrent.Y-(e.Y-ptMouseDown.Y))<0)
ptCurrent.Y=0;
else
ptCurrent.Y-=(e.Y-ptMouseDown.Y);
}
} if(e.Y<ptMouseDown.Y)
{
if((sShowing.Height>=Screen.PrimaryScreen.Bounds.Height)
&&((ptCurrent.Y+sShowing.Height)!=bitCurrent.Height))
{
blnYChanged=true;
if((ptCurrent.Y+(ptMouseDown.Y-e.Y)+sShowing.Height)<bitCurrent.Height)
ptCurrent.Y+=(ptMouseDown.Y-e.Y);
else
ptCurrent.Y=bitCurrent.Height-sShowing.Height;
}
} if(e.X>ptMouseDown.X)
{
if((sShowing.Width>=Screen.PrimaryScreen.Bounds.Width)
&&(ptCurrent.X!=0))
{
blnXChanged=true;
if((ptCurrent.X-(e.X-ptMouseDown.X))<0)
ptCurrent.X=0;
else
ptCurrent.X-=(e.X-ptMouseDown.X);
}
} if(e.X<ptMouseDown.X)
{
if((sShowing.Width>=Screen.PrimaryScreen.Bounds.Width)
&&((ptCurrent.X+sShowing.Width)!=bitCurrent.Width))
{
if((ptCurrent.X+(ptMouseDown.X-e.X)+sShowing.Width)<bitCurrent.Width)
ptCurrent.X+=(ptMouseDown.X-e.X);
else
ptCurrent.X=bitCurrent.Width-sShowing.Width;
}
} //Then redraw
if(blnXChanged||blnYChanged)
this.OnPaint(new PaintEventArgs(this.CreateGraphics(),this.Bounds));
ptMouseDown.X=e.X;
ptMouseDown.Y=e.Y;
//Thread.Sleep(50);
}
} private void frmFullScreen_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
if(e.Button==MouseButtons.Left)
{
ptMouseDown.X=e.X;
ptMouseDown.Y=e.Y;
}
}
}
}