怎样做选择框

Question

我现在想做一个用来在图像上选择用的徒有矩形框（就是按住鼠标拖出一个矩形，在ＶＣ＋＋中叫CRectTracker），我用了两种方法
１）先画出背景图．每移动一下鼠标改变选择矩形大小，并对需要重画的区域调用Invalidate.结果是闪烁严重
２）我把图形设成窗体的BackgroundImage，然后做上面的动作，不闪烁了，但移动时处理特别慢，感觉拖动不连贯．
不知道各们大侠是怎么为的？

Answer 1

试试这个吧，管用using System;
using System.Windows.Forms;
using System.Drawing;namespace CaptureScreen
{
/// <summary>
/// Rubberband 的摘要说明。
/// 实现选择框的功能
/// </summary>
public class Rubberband
{
protected Control parent;
private Point lastLeftTop = new Point();
private Point lastRightBottom = new Point();
private Point startPoint;
public  Rectangle rect = Rectangle.Empty; public Rubberband(Control theParent, Point theStartingPoint)
{
this.startPoint = theStartingPoint;
parent = theParent;
parent.Capture = true;
Cursor.Clip = parent.RectangleToScreen(parent.ClientRectangle);
rect = new Rectangle(this.startPoint.X, this.startPoint.Y, 0, 0);
} public Point SelectedLT
{
get{return this.startPoint;}
set{this.startPoint = value;}
} public Point SelectedRB
{
get{return this.lastRightBottom;}
} public Point LeftTop
{
get{return rect.Location;}
} public void End()
{
Cursor.Clip = Rectangle.Empty;
parent.Capture = false; // erase the rubberband
//Draw();
rect = Rectangle.Empty;
} public void Move(Point thePoint,int distX,int distY,Point startPoint)
{
rect.Location = new Point(thePoint.X - distX,thePoint.Y - distY);
this.startPoint = rect.Location;
//rect.Location = new Point(rect.Location.X + (thePoint.X - startPoint.X),rect.Location.Y + thePoint.Y - startPoint.Y);
Draw();
} public void ResizeTo(Point thePoint)
{
// erase the old rubberband
Draw(); // get the new size of the rubberband
rect.Width =  thePoint.X - rect.Left;
rect.Height = thePoint.Y - rect.Top; // draw the new rubberband
Draw();
} public void Stop(Point thePoint,int distX,int distY)
{
rect.Location = new Point(thePoint.X - distX,thePoint.Y - distY);
//this.startPoint = rect.Location;
//rect = Bounds();
Draw();
} public Rectangle Bounds()
{
// return a normalized rectangle, i.e. a rect
// where (left <= right) and (top <= bottom)
if ( (rect.Left > rect.Right) || (rect.Top > rect.Bottom) )
{
int left = Math.Min(rect.Left, rect.Right);
int right = Math.Max(rect.Left, rect.Right);
int top = Math.Min(rect.Top, rect.Bottom);
int bottom = Math.Max(rect.Top, rect.Bottom); /*
this.lastLeftTop = new Point(left,top);
this.lastRightBottom = new Point(right,bottom);
*/ return Rectangle.FromLTRB(left, top, right, bottom);
} return rect;
} // Reversible drawing method
// Calling theis method the first time draws the rubberband.
// Calling it a second time with the same rect erases the rubberband
protected void Draw()
{
Rectangle r = parent.RectangleToScreen(rect);
//Rectangle r = parent.RectangleToScreen(rect);
ControlPaint.DrawReversibleFrame(r, Color.Black ,FrameStyle.Dashed);
//ControlPaint.DrawReversibleFrame(r, Color.Black, FrameStyle.Dashed);
}
}
}