局部刷新

绘制线过移动鼠标程中绘制临时线段防闪烁

　　参考OpenS-CAD想实现绘制线的功能。希望实现绘制线的过程，在移动线的时候没有闪烁和花屏。但是出现了问题，困扰了2天，前天熬的太晚，搞得现在精力都没有恢复。现在终于把问题搞清楚了：

　　第一个问题：没有给背景图片赋颜色，此时相当于透明。所以每次将图片局部范围重绘产生严重的花屏，绘制的线段残留在屏幕上，将透明的东西绘制是不可能将移动过程中产生的临时线段擦除的。

　　第二个问题：用当前移动产生的线段包围盒来重绘，其实在本次鼠标移动过程中，应该将上次产生的残留擦除，用上次的包围盒局部重绘。

　　以下是自己写的一个控件的雏形：

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using RGeos.Geometry;
using System.Drawing.Imaging;

namespace RGeos.PluginEngine
{
public partial class UcMapControl2 : UserControl, IRMapControl
{
private ITool mCurrentTool = null;

public ITool CurrentTool
{
get { return mCurrentTool; }
set { mCurrentTool = value; }
}
public REnvelope mExtent { get; set; }
public Map mMap { get; set; }

private PointF m_panOffset = new PointF(25, -25);

public PointF PanOffset
{
get { return m_panOffset; }
set { m_panOffset = value; }
}
private PointF m_dragOffset = new PointF(0, 0);

public PointF DragOffset
{
get { return m_dragOffset; }
set { m_dragOffset = value; }
}
public UcMapControl2()
{
InitializeComponent();
mMap = new Map();
this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true);
this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
}

bool m_staticDirty = true;
//缓存图片？
Bitmap m_staticImage = null;
System.Drawing.Drawing2D.SmoothingMode m_smoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighSpeed;
protected override void OnPaint(PaintEventArgs e)
{
Tracing.StartTrack(Program.TracePaint);
#region old
e.Graphics.SmoothingMode = m_smoothingMode;
Rectangle cliprectangle = e.ClipRectangle;
if (m_staticImage == null)
{
cliprectangle = ClientRectangle;
m_staticImage = new Bitmap(ClientRectangle.Width, ClientRectangle.Height);
//m_staticImage.Save("D:\\a.png", ImageFormat.Png);
m_staticDirty = true;
}
//绘制在背景图片上
Graphics BitMapGc = Graphics.FromImage(m_staticImage);
BitMapGc.SmoothingMode = m_smoothingMode;
//绘制背景，注意如果不设将为透明色
BitMapGc.Clear(Color.White);
//this.BackgroundLayer.Draw(dcStatic, r);
//if (m_model.GridLayer.Enabled)
// m_model.GridLayer.Draw(dcStatic, r);
//绘制十字丝
RPoint rCenterPoint = new RPoint(0, 0, 0);
PointF nullPoint = Transform.ToScreen(rCenterPoint, this);
BitMapGc.DrawLine(Pens.Blue, nullPoint.X - 10, nullPoint.Y, nullPoint.X + 10, nullPoint.Y);
BitMapGc.DrawLine(Pens.Blue, nullPoint.X, nullPoint.Y - 10, nullPoint.X, nullPoint.Y + 10);
if (m_staticDirty)
{
m_staticDirty = false;

List<ILayer> layers = mMap.Layers;
for (int layerindex = layers.Count - 1; layerindex >= 0; layerindex--)
{
//if (layers[layerindex].Visible)
//layers[layerindex].Draw();
}
BitMapGc.Dispose();
}
//绘制背景图片
e.Graphics.DrawImage(m_staticImage, cliprectangle, cliprectangle, GraphicsUnit.Pixel);
//绘制新建对象
//if (m_newObject != null)
// m_newObject.Draw(dc, r);
#endregion
Tracing.EndTrack(Program.TracePaint, "OnPaint complete");

}

protected override void OnResize(EventArgs e)
{
base.OnResize(e);
if (m_lastCenterPoint != null && Width != 0)
SetCenterScreen(Transform.ToScreen(m_lastCenterPoint, this), false);
m_lastCenterPoint = CenterPointUnit();
m_staticImage = null;
Invalidate();
}
RPoint m_lastCenterPoint;
/// <summary>
/// 设置画布到屏幕的中心
/// </summary>
/// <param name="rPoint">直角坐标系坐标</param>
public void SetCenter(RPoint unitPoint)
{
PointF point = Transform.ToScreen(unitPoint, this);
m_lastCenterPoint = unitPoint;
SetCenterScreen(point, false);
}

protected void SetCenterScreen(PointF screenPoint, bool setCursor)
{
float centerX = ClientRectangle.Width / 2;
m_panOffset.X += centerX - screenPoint.X;

float centerY = ClientRectangle.Height / 2;
m_panOffset.Y += centerY - screenPoint.Y;

if (setCursor)
Cursor.Position = this.PointToScreen(new Point((int)centerX, (int)centerY));
Invalidate();
}
public RPoint CenterPointUnit()
{
RPoint p1 = Transform.ToUnit(new PointF(0, 0), this);
RPoint p2 = Transform.ToUnit(new PointF(this.ClientRectangle.Width, this.ClientRectangle.Height), this);
RPoint center = new RPoint();
center.X = (p1.X + p2.X) / 2;
center.Y = (p1.Y + p2.Y) / 2;
return center;
}
protected override void OnMouseUp(MouseEventArgs e)
{
base.OnMouseUp(e);

}
int n = 0;
PointF p1;
PointF TempPoint2;//缓存移动过程中产生的第二个点，上一移动过程中
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);

Rectangle invalidaterect = Rectangle.Empty;
if (n < 1)
{

}
else
{
//REnvelope env = mNewLine.GetBoundingBox();
//mNewLine.P1 = new RPoint(e.X, e.Y, 0);

double xmin = Math.Min(p1.X, TempPoint2.X);
double ymin = Math.Min(p1.Y, TempPoint2.Y);
double w = Math.Abs(p1.X - TempPoint2.X);
double h = Math.Abs(p1.Y - TempPoint2.Y);
invalidaterect = new Rectangle((int)xmin, (int)ymin, (int)w, (int)h);
invalidaterect.Inflate(2, 2);

Pen pen = new Pen(Color.Red);
//擦除上次移动绘制的线，通过重绘上次移动范围区域的缓存图片实现
RepaintStatic(invalidaterect);
//Bitmap m_staticImage2 = new Bitmap(invalidaterect.Width, invalidaterect.Height);
//m_staticImage2.Save("D:\\adfghj.png", ImageFormat.Png);
pen.EndCap = System.Drawing.Drawing2D.LineCap.Round;
pen.StartCap = System.Drawing.Drawing2D.LineCap.Round;
Graphics dc = Graphics.FromHwnd(Handle);
dc.SmoothingMode = m_smoothingMode;
Point p2 = new Point(e.X, e.Y);
dc.DrawLine(pen, p1, p2);
dc.Dispose();
TempPoint2 = p2;
//Invalidate();
//DoInvalidate(false, invalidaterect);

}
}
protected override void OnMouseDown(MouseEventArgs e)
{
n++;
if (n <= 1)
{
//mNewLine = new RSegment();
//mNewLine.P0 = new RPoint(e.X, e.Y, 0);
//mNewLine.P1 = new RPoint();
//初始化两个点，注意此处两点相同。
p1 = new PointF(e.X, e.Y);
TempPoint2 = new Point(e.X, e.Y);
Invalidate(true);
}
base.OnMouseDown(e);
}
public void DoInvalidate(bool dostatic, Rectangle rect)
{
if (dostatic)
m_staticDirty = true;
Invalidate(rect);
}
/// <summary>
/// 局部刷新，重新绘制图片Bitmap无效区域
/// </summary>
/// <param name="r"></param>
public void RepaintStatic(Rectangle r)
{
if (m_staticImage == null)
return;
Graphics dc = Graphics.FromHwnd(Handle);
if (r.X < 0) r.X = 0;
if (r.X > m_staticImage.Width) r.X = 0;
if (r.Y < 0) r.Y = 0;
if (r.Y > m_staticImage.Height) r.Y = 0;

if (r.Width > m_staticImage.Width || r.Width < 0)
r.Width = m_staticImage.Width;
if (r.Height > m_staticImage.Height || r.Height < 0)
r.Height = m_staticImage.Height;
dc.DrawImage(m_staticImage, r, r, GraphicsUnit.Pixel);
Image temp = new Bitmap(m_staticImage);
Graphics gc = Graphics.FromImage(temp);
gc.DrawLine(Pens.Blue, r.Location, new Point(r.Location.X + r.Width, r.Location.Y + r.Height));
gc.Dispose();
temp.Save("d:\\AAAA.png", ImageFormat.Png);
m_staticImage.Save("d:\\BBBB.png", ImageFormat.Png);
dc.Dispose();
}
public float ScreenHeight()
{
return (float)(Transform.ToUnit(this.ClientRectangle.Height, this as IRMapControl));
}
private float mZoom = 1.0f;
public float Zoom
{
get
{
return mZoom;
}
set
{
mZoom = value;
}
}
}
}

UcMapControl2