绘图板【或画板】

<img src="http://img.blog.csdn.net/20150419002147281?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvWWFuZ1J1bmthbmdCbGE=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast" alt="" />

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;
using System.Drawing.Drawing2D;
namespace Draw
{
public partial class PrintForm : Form
{
public PrintForm()
{
InitializeComponent();
}
#region   成员变量
Graphics g = null;//画布，在窗体加载事件中生成
Pen p = null;//笔，在窗体加载的时间中生成
//  Brush b = new ;//填充
Brush b = null;
Color color = Color.Black;//画笔的颜色，默认为黑色
string shape = "";//绘什么图形
float width = 1;//笔的粗细，默认为1
Point beginPoint = new Point();//开始的点坐标，在鼠标按下事，进行获取
Point endPoint = new Point();//结束的点坐标，在鼠标释放时，进行获取

#endregion

#region 加载事件只负责初始化  设置笔的粗细  颜色的选择
/// <summary>
/// 颜色的选择
/// </summary>
private void 选择颜色ToolStripMenuItem_Click(object sender, EventArgs e)
{
//接受用户选择的按钮，这个按钮为颜色控件上的按钮
DialogResult result= this.colorDialog1.ShowDialog();
if (result == DialogResult.OK)//如果用户选择了Ok按钮
{
color = this.colorDialog1.Color;//获取用户选择的颜色

}
}

private void PrintForm_Load(object sender, EventArgs e)
{
//在窗体的加载事件中创建Panel控件的Graphics
g = this.panelDraw.CreateGraphics();
p = new Pen(color, width);//设置笔的颜色和粗细

}

//设置笔的粗细
private void toolStripTextBox2_TextChanged(object sender, EventArgs e)
{
try
{
width = Convert.ToInt32(this.toolStripTextBox2.Text);
}
catch (Exception)
{
MessageBox.Show("请输入有效的内容");
}
}

#endregion

#region  逻辑的处理
bool isMouseUp = false;//鼠标是否释放
bool isMouseDown = false;//鼠标是否按下
//   bool roundPaint = false;//控制圆只画一次
#endregion

//在panel控件上,按下鼠标
private void panelDraw_MouseDown(object sender, MouseEventArgs e)
{
if (!isMouseUp)//在释放鼠标之前,进if
{
beginPoint.X = e.X;
beginPoint.Y = e.Y;
isMouseUp = true;//记录下来之后，就把鼠标的状态isMouseUp设为true,给下面的鼠标移动使用

}

}

//在panel控件上，处理鼠标的移动
private void panelDraw_MouseMove(object sender, MouseEventArgs e)
{
if (shape == "")
{
convenientlyPaint(sender, e);
return;
}
if (shape == "橡皮擦")
{
xiangpicao(sender, e);
return;
}

if (shape == "空心圆" && isMouseUp)//光是一个条件，圆会一直重复花，而且会重叠，所以得在来一个条件，就是鼠标释放时，画一次，画最后的一次
{
BlankRound(sender,e);
return;
}

}

#region 随手绘
/// <summary>
/// 随手绘制图形
/// </summary>
/// <param name="sender"></param>//巧妙的地方 传参
3ff0
/// <param name="e"></param>
public void convenientlyPaint(object sender, MouseEventArgs e)
{
if (isMouseUp)//在移动过程中，如果释放
{
endPoint.X = e.X;
endPoint.Y = e.Y;
g.DrawLine(p, beginPoint, endPoint);
}
//重写设置起点---->轨迹
beginPoint.X = e.X;
beginPoint.Y = e.Y;
//如果不设置，是使用默认的，设置了，是使用设置后的
p.Color = color;
p.Width = width;
}

public void xiangpicao(object sender, MouseEventArgs e)
{
if (isMouseUp)//在移动过程中，如果释放
{
endPoint.X = e.X;
endPoint.Y = e.Y;
g.DrawLine(p, beginPoint, endPoint);
}
//重写设置起点---->轨迹
beginPoint.X = e.X;
beginPoint.Y = e.Y;
//如果不设置，是使用默认的，设置了，是使用设置后的
p.Color = Color.White;
p.Width = 5;
}

#endregion

/// <summary>
/// 绘制空心圆
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
public void BlankRound(object sender, MouseEventArgs e)
{

if (isMouseUp)//在移动过程中，如果释放
{
endPoint.X = e.X;
endPoint.Y = e.Y;
}
}

//当我鼠标释放时，停止绘图--->说白了，一切恢复到初始化之前
private void panelDraw_MouseUp(object sender, MouseEventArgs e)
{
isMouseUp = false;//鼠标是否释放

isMouseDown = false;//鼠标是否按下
//beginPoint = new Point();//起点坐标初始化，下次点击就有了---------------被这行代码坑死了
endPoint.X = e.X;
endPoint.Y = e.Y;

if (shape == "空心圆")//是可以的
{
p.Color = color;
p.Width = width;
g.DrawEllipse(p, beginPoint.X, beginPoint.Y, Math.Abs(beginPoint.X - endPoint.X), Math.Abs(beginPoint.Y - endPoint.Y));
}

if (shape == "实心圆")//是可以的
{
p.Color = color;
p.Width = width;
SolidBrush solidBrush = new SolidBrush(color);
Rectangle rec=new Rectangle(beginPoint.X, beginPoint.Y, Math.Abs(beginPoint.X - endPoint.X), Math.Abs(beginPoint.Y - endPoint.Y));
g.FillEllipse(solidBrush,rec);
g.DrawEllipse(p, beginPoint.X, beginPoint.Y, Math.Abs(beginPoint.X - endPoint.X), Math.Abs(beginPoint.Y - endPoint.Y));
}

if( shape == "直线")
{
p.Color = color;
p.Width = width;
g.DrawLine(p, beginPoint, endPoint);
}
if (shape == "空心正方形")
{
p.Color = color;
p.Width = width;
Rectangle rec = new Rectangle(beginPoint.X, beginPoint.Y, Math.Abs(beginPoint.X - endPoint.X), Math.Abs(beginPoint.Y - endPoint.Y));
g.DrawRectangle(p,rec);
}

if (shape == "实心正方形")
{
p.Color = color;
p.Width = width;

SolidBrush solidBrush = new SolidBrush(color);
Rectangle rec = new Rectangle(beginPoint.X, beginPoint.Y, Math.Abs(beginPoint.X - endPoint.X), Math.Abs(beginPoint.Y - endPoint.Y));
g.FillRectangle(solidBrush, rec);

g.DrawRectangle(p, rec);
}
}

#region  用户选择绘制的具体图形

private void 绘图ToolStripMenuItem_Click_1(object sender, EventArgs e)
{
shape = "空心圆";
}

private void toolStripMenuItem1_Click_1(object sender, EventArgs e)
{
shape = "实心圆";

}

private void 直线ToolStripMenuItem_Click_1(object sender, EventArgs e)
{
shape = "直线";
}

private void 正方形ToolStripMenuItem_Click_1(object sender, EventArgs e)
{
shape = "空心正方形";
}

private void 实心正方形ToolStripMenuItem_Click_1(object sender, EventArgs e)
{
shape = "实心正方形";
}

private void 笔的粗细ToolStripMenuItem_Click(object sender, EventArgs e)
{
shape = "";
}
#endregion

private void 橡皮擦ToolStripMenuItem_Click(object sender, EventArgs e)
{
shape = "橡皮擦";
}

private void 清空画板ToolStripMenuItem_Click(object sender, EventArgs e)
{
this.panelDraw.Invalidate();

}
}
}