form1.cs

实现了c#窗体编程的部分功能

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;



namespace FormDraw
{
    public partial class DrawForm : Form
    {
        Color col = Color.Green;
        Pen pen = new Pen(Color.Green, 3);
        Brush brush = new SolidBrush(Color.Green);
        bool fill;
        public DrawForm()
        {
            InitializeComponent();
            setColButton.BackColor = col; // col为类变量，初值为Color.Green
            fill = false;
        }

        private void OnFileOpen(object sender, EventArgs e)
        {
            if (openFileDlg.ShowDialog() == DialogResult.OK)
            {
                string fn = openFileDlg.FileName;
                MessageBox.Show(string.Format("你选择的文件名为：{0}", fn), "文件名");
            }

        }

        private void OnFileNew(object sender, EventArgs e)
        {
            MessageBox.Show("创建新文档？", "请选择", MessageBoxButtons.YesNo);
        }

        private void OnExit(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void OnFileOpenMouseHover(object sender, MouseEventArgs e)
        {
            promptLabel.Text = "打开文档文件";
        }

        private void OnFileOpenMouseLeave(object sender, EventArgs e)
        {
            promptLabel.Text = "就绪";
        }

        private void OnMouseMove(object sender, MouseEventArgs e)
        {
             if (mouseDown) // mouseDown为bool型类变量
            {
                int l, t, r, b; // 定义矩形坐标的变量
                Graphics graph = drawPanel.CreateGraphics(); // 创建图形对象
                IntPtr hdc = graph.GetHdc(); // 获取DC句柄
                Point point = new Point(0, 0); // 定义点对象（用于MoveToEx函数的输出参数）
                IntPtr hPen = GDI.CreatePen(2, 0, 0x808080); // 创建灰色单像素点线笔
                IntPtr hOldPen = GDI.SelectObject(hdc, hPen); // 选入灰笔
                IntPtr hOldBrush = GDI.SelectObject(hdc, GDI.GetStockObject(5)); // 选入空刷
                GDI.SetBkMode(hdc, 1); // 设置透明背景模式
                GDI.SetROP2(hdc, 7); // 设置异或绘图模式

                switch (drawType)
                {
                    case DrawTypes.line: // 画动态直线
                        if (drawn) // 擦除，下同
                        {
                            GDI.MoveToEx(hdc, x0, y0, out point);
                            GDI.LineTo(hdc, x, y); 
                        }
                        GDI.MoveToEx(hdc,x0, y0, out point); 
                        GDI.LineTo(hdc, e.X, e.Y);
                        break;
                    case DrawTypes.rect:  // 画动态矩形
                        if (drawn)
                        {
                            l = Math.Min(x0, x); r = Math.Max(x0, x);
                            t = Math.Min(y0, y); b = Math.Max(y0, y);
                            GDI.Rectangle(hdc, l, t, r, b);
                        }
                        l = Math.Min(x0, e.X); r = Math.Max(x0, e.X);
                        t = Math.Min(y0, e.Y); b = Math.Max(y0, e.Y);
                        GDI.Rectangle(hdc, l, t, r, b);
                        break;
                    case DrawTypes.ellipse: // 画动态椭圆
                        if (drawn)
                        {
                            l = Math.Min(x0, x); r = Math.Max(x0, x);
                            t = Math.Min(y0, y); b = Math.Max(y0, y);
                            GDI.Ellipse(hdc, l, t, r, b);
                        }
                        l = Math.Min(x0, e.X); r = Math.Max(x0, e.X);
                        t = Math.Min(y0, e.Y); b = Math.Max(y0, e.Y);
                        GDI.Ellipse(hdc, l, t, r, b);
                        break;
                }
                GDI.SelectObject(hdc, hOldPen); // 选入老笔
                GDI.DeleteObject(hPen); // 删除创建的灰笔
                GDI.SetROP2(hdc, 7); // 设置覆盖绘图模式
                graph.ReleaseHdc(hdc); // 释放DC句柄
                x = e.X; y = e.Y; // 记录当前终点
                drawn = true; // 设置已绘图为真
            }

            xValueLabel.Text = e.X.ToString();
            yValueLabel.Text = e.Y.ToString();
        }

        private void OnSetCol(object sender, EventArgs e)
        {
            setColDlg.Color = col;
            if (setColDlg.ShowDialog() == DialogResult.OK)
            {
                col = setColDlg.Color;
                pen = new Pen(col, 3);
                brush = new SolidBrush(col);
                setColButton.BackColor = col;
            }
        }
        enum DrawTypes { line, rect, ellipse }
        DrawTypes drawType = DrawTypes.line;
        bool mouseDown = false, drawn = false;
        int x0, y0, x, y;


        public class GDI
        {
            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern IntPtr CreatePen(
                int fnPenStyle,
                int nWidth,
                uint crColor
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern IntPtr GetStockObject(
                int fnObject
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern IntPtr SelectObject(
                IntPtr hdc,
                IntPtr hgdiobj
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern bool DeleteObject(
                IntPtr hObject
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern int SetBkMode(
                IntPtr hdc,
                int nBkMode
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern int SetROP2(
                 IntPtr hdc,
                 int nDrawMode
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern bool MoveToEx(
                 IntPtr hdc,
                 int X, int Y,
                 out Point point
              );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern bool LineTo(
                IntPtr hdc,
                int nXEnd, int nYEnd
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern bool Rectangle(
               IntPtr hdc,
               int ulCornerX, int ulCornerY,
               int lrCornerX, int lrCornerY
            );

            [System.Runtime.InteropServices.DllImport("gdi32.dll")]
            internal static extern bool Ellipse(
               IntPtr hdc,
               int x1, int y1, int x2, int y2
            );

        }

        private void OnMouseDown(object sender, MouseEventArgs e)
        {
            mouseDown=true;
            x0 = e.X; y0 = e.Y;
            x = x0; y = y0;

        }

        private void OnMouseUp(object sender, MouseEventArgs e)
        {
            if (mouseDown)
            {
                int l, t, w, h;
                Graphics graph = drawPanel.CreateGraphics();
                if (drawn) // 擦除
                {
                    int r, b;
                    IntPtr hdc = graph.GetHdc();
                    Point point;
                    IntPtr hPen = GDI.CreatePen(2, 0, 0x808080);
                    IntPtr hOldPen = GDI.SelectObject(hdc, hPen);
                    IntPtr hOldBrush = GDI.SelectObject(hdc, GDI.GetStockObject(5));
                    GDI.SetBkMode(hdc, 1);
                    GDI.SetROP2(hdc, 7);

                    switch (drawType)
                    {
                        case DrawTypes.line:
                            GDI.MoveToEx(hdc, x0, y0, out point);
                            GDI.LineTo(hdc, x, y);
                            break;
                        case DrawTypes.rect:
                            l = Math.Min(x0, x); r = Math.Max(x0, x);
                            t = Math.Min(y0, y); b = Math.Max(y0, y);
                            GDI.Rectangle(hdc, l, t, r, b);
                            break;
                        case DrawTypes.ellipse:
                            l = Math.Min(x0, x); r = Math.Max(x0, x);
                            t = Math.Min(y0, y); b = Math.Max(y0, y);
                            GDI.Ellipse(hdc, l, t, r, b);
                            break;
                    }
                    GDI.SelectObject(hdc, hOldPen);
                    GDI.DeleteObject(hPen);
                    GDI.SetROP2(hdc, 7);
                    graph.ReleaseHdc(hdc);
                }
                switch (drawType) // 绘图
                {
                    case DrawTypes.line:
                        graph.DrawLine(pen, x0, y0, e.X, e.Y);
                        break;
                    case DrawTypes.rect:
                        l = Math.Min(x0, e.X); t = Math.Min(y0, e.Y);
                        w = Math.Abs(e.X - x0); h = Math.Abs(e.Y - y0);
                        if (fill== true) graph.FillRectangle(brush, l, t, w, h);
                        graph.DrawRectangle(pen, l, t, w, h);
                        break;
                    case DrawTypes.ellipse:
                        l = Math.Min(x0, e.X); t = Math.Min(y0, e.Y);
                        w = Math.Abs(e.X - x0); h = Math.Abs(e.Y - y0);
                        if (fill == true) graph.FillEllipse(brush, l, t, w, h);
                        graph.DrawEllipse(pen, l, t, w, h);
                        break;
                }
                mouseDown = false;
            }

        }

        private void OnSetDline(object sender, EventArgs e)
        {
            drawType = DrawTypes.line;
        }

        private void OnSetDrect(object sender, EventArgs e)
        {
            drawType = DrawTypes.rect;
        }

        private void OnSetDellipse(object sender, EventArgs e)
        {
            drawType = DrawTypes.ellipse;
        }

        private void OnSetFill(object sender, EventArgs e)
        {
            fill = !fill;
        }

    }
}