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;

        //画笔句柄
        private IntPtr g_hPen;

        IntPtr g_hdc;

        IntPtr g_oldp;

        IntPtr g_oldb;

        #endregion

        public Form1()
        {
            InitializeComponent();

            bmp = new Bitmap(System.IO.Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase) + "\\PIC\\a20.bmp");

            //图片句柄
            int ibmp = bmp.GetHbitmap().ToInt32();

            //画刷句柄
            g_hBrush = CreatePatternBrush(ibmp);

            ScreenGraphics = this.CreateGraphics();

            imgOffscreen = new Bitmap(240, 320);

            BufferGraphics = Graphics.FromImage(imgOffscreen);

            BufferGraphics.FillRectangle(new SolidBrush(Color.White), new Rectangle(0, 0, 240, 320));

            g_hdc = BufferGraphics.GetHdc();

            g_hPen = CreatePen(NULL_PEN, 1, 0);

            IntPtr oldp = SelectObject(g_hdc, g_hPen);

            IntPtr oldb = SelectObject(g_hdc, g_hBrush);

        }

        //private void Form1_Paint(object sender, PaintEventArgs e)
        //{

           
        //}

        protected override void OnPaint(PaintEventArgs e)
        {
            ScreenGraphics.DrawImage(imgOffscreen, 0, 0);
        }

        protected override void OnPaintBackground(PaintEventArgs e)
        {
            //base.OnPaintBackground(e);
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            IsDown = true;
        }

        /// <summary>
        /// 颜色值转换
        /// </summary>
        /// <param name="color"></param>
        /// <returns></returns>
        private static int ColorToCOLORREF(Color color)
        {
            return ((color.R | (color.G << 8)) | (color.B << 16));
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {

            Ellipse(g_hdc, e.X - 10, e.Y - 10, e.X + 10, e.Y + 10);

            this.Invalidate();
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            IsDown = false;
        }

        ~Form1()
        {
            SelectObject(g_hdc, g_oldb);

            SelectObject(g_hdc, g_oldp);

            DeleteObject(g_hBrush);

            DeleteObject(g_hPen);

            BufferGraphics.ReleaseHdc(g_hdc);
        }

    }
}