wince 绘图中使用橡皮擦

这里说的绘图使用橡皮擦，就是把蒙在表面的图片擦掉，显示里面的图片。

原理很简单，就是用被蒙着的图片来创建一个画刷，然后在mousemove里面绘图就可以了

代码如下：

using System;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Runtime.InteropServices;

using System.Reflection;

namespace phone_r1

{

public partial class Form1 : Form

{

[DllImport("coredll.dll",EntryPoint="CreatePen")]

public static extern IntPtr CreatePen(int nPenStyle, int nWidth, int color);

[DllImport("coredll.dll", EntryPoint = "CreatePatternBrush")]

public static extern IntPtr CreatePatternBrush(int hBitmap);

[DllImport("coredll.dll", EntryPoint = "SelectObject")]

private extern static IntPtr SelectObject(IntPtr hdc, IntPtr obj);

[DllImport("coredll.dll", EntryPoint = "DeleteObject")]

private extern static bool DeleteObject(IntPtr obj);

[DllImport("coredll.dll", EntryPoint = "Ellipse")]

private extern static bool Ellipse(IntPtr hdc,int x1,int y1,int x2,int y2 );

private const int NULL_PEN = 5;

//string[] strArr;

//屏幕绘图对象

private Graphics ScreenGraphics;

//内存绘图对象

private Graphics BufferGraphics;

//内存图

private Bitmap imgOffscreen;

bool IsDown = false;

Bitmap bmp;

#region ......

//画刷句柄

private IntPtr g_hBrush;