如标题所言，使用System.Drawing类来实现简单图形的绘制，这个项目使用C#语言进行winform窗体应用开发，主要功能有：绘制直线、绘制矩形、绘制圆形、ESC结束绘制、清空画布。
窗体设计窗体设计如下图所示：主要分成三个部分四个区域对窗体进行设计（窗体的控制代码放在最后）。
自定义绘制类（绘制类代码放在最后），包括绘制方法、鼠标事件、按键事件等方法的具体实现，绘制方法集成直线、矩形、圆形的绘制代码，鼠标事件包括按下事件、抬起事件、移动事件，按键事件只有ESC结束绘制。
1.绘制方法绘制方法需要设定画布Graphics、画笔Pen等内容，并通过DrawLine()、DrawRectangle()、DrawEllipse()实现画直线、矩形、圆形。如下代码所示：
Pen pen = new Pen(Color.Black, 1);//实例化画笔
Graphics graphics = this.panel3.CreateGraphics();//基于绘图区Panel3创建画布
……
graphics.DrawLine(Pen pen, float x1, float y1, float x2, float y2)；//基于起止点的坐标绘制直线
graphics.DrawRectangle(Pen pen, float x, float y, float width, float height);//基于点的坐标和长宽绘制矩形
graphics.DrawEllipse(Pen pen, float x, float y, float width, float height);//基于点的坐标和长宽绘制圆形但是上面的绘图方法在直接调用时，绘制矩形和圆形都有一定的局限。绘制矩形只能从左上角进行绘制，绘制圆形时只能通过外接矩形进行绘制（在类方法元数据中有说明，可自行查看），不符合我们实际绘图的需求，因此需要对方法的进行一点修正。具体如下
//绘制矩形
float px, py, width, height;
px = Math.Min(float x1, float x2);//获取一下矩形最左上角的坐标位置
py = Math.Min(float y1, float y2);
width = Math.Abs(float x1 - float x2);//长宽的计算不变
height = Math.Abs(float y1 - float y2);
graphics.DrawRectangle(pen, px, py, width, height);//可以任意方向绘制矩形
……
//绘制圆形
float r, rx, ry, rw, rh;
r = (float)Math.Sqrt((float x1 - float x2) * (float x1 - float x2) + (float y1 - float y2) * (float y1 - float y2));//计算半径
rx = item[1] - r;//计算外接矩形最左上角坐标
ry = item[2] - r;
rw = r + r;//计算长宽
rh = r + r;
graphics.DrawEllipse(pen, rx, ry, rw, rh);//通过圆心加半径绘制圆形鼠标事件主要是按下MouseDown、抬起MouseUp、移动MouseMove三个事件，当鼠标按下时记录起点坐标，鼠标按住不松移动时记录路径点坐标、鼠标松开抬起时记录结束点坐标；在这其中，鼠标按下、抬起负责对结果数据的记录，鼠标移动负责对过程数据的记录并中间过程图形。他们之间具有一定逻辑关系，如下代码所示：
// 鼠标按下
private void panel3_MouseDown(object sender, MouseEventArgs e)
{
m_draw.MouseDownData(e.X, e.Y);//记录起点数据
this.panel3.MouseMove += panel3_MouseMove;//注册鼠标移动事件
}
// 鼠标抬起
private void panel3_MouseUp(object sender, MouseEventArgs e)
{
this.panel3.MouseMove -= panel3_MouseMove;//取消册鼠标移动事件
m_draw.MouseUpData(e.X, e.Y);//记录结果数据
}
// 鼠标移动
private void panel3_MouseMove(object sender, MouseEventArgs e)
{
m_draw.DrawingCad(e.X, e.Y);//鼠标移动路径点数据并绘制草图
}1.ESC结束绘制的事件，直接看代码：
/// Esc结束绘制
private void DrawForm_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)27)//判断是否按下ESC键
{
this.panel3.MouseDown -= panel3_MouseDown;//取消各类事件
this.panel3.MouseUp -= panel3_MouseUp;
this.panel3.MouseMove -= panel3_MouseMove;
if (drawIng == 2)//drawIng 判断绘制状态
{
drawIng = 0;
m_draw.CloseDraw();//实现结束后的绘图
}
}
}2.清空方法，清空很简单，使用Clear()，用白色进行清空，如下：
graphics.Clear(Color.White);看下面视频：
绘图演示
完整代码主窗体代码
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace HuiTu
{
public partial class DrawForm : Form
{
//实例化绘图类
Draw m_draw;
//绘图状态(0没有绘制，1等待绘制，2正在绘制)
int drawIng;
public DrawForm()
{
InitializeComponent();
drawIng = 0;
m_draw = new Draw(this.panel3.CreateGraphics());
}
////// 绘制直线
/// //////private void toolStripMenuItem1_Click(object sender, EventArgs e)
{
m_draw.SetType(0);
RegisterForevents();
this.label1.Text = "按住鼠标左键移动画线";
}
////// 绘制矩形
/// //////private void toolStripMenuItem2_Click(object sender, EventArgs e)
{
m_draw.SetType(1);
RegisterForevents();
this.label1.Text = "按住鼠标左键移动画矩形";
}
////// 绘制圆形
/// //////private void toolStripMenuItem3_Click(object sender, EventArgs e)
{
m_draw.SetType(2);
RegisterForevents();
this.label1.Text = "按住鼠标左键移动画圆";
}
////// 注册绘图鼠标事件
/// private void RegisterForevents()
{
if (drawIng == 0)
{
drawIng = 1;
this.panel3.Cursor = Cursors.Cross;
this.panel3.MouseDown += panel3_MouseDown;
this.panel3.MouseUp += panel3_MouseUp;
}
}
////// 鼠标按下
/// //////private void panel3_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
drawIng = 2;
m_draw.MouseDownData(e.X, e.Y);
this.panel3.MouseMove += panel3_MouseMove;
}
}
////// 鼠标抬起
/// //////private void panel3_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
drawIng = 1;
this.panel3.MouseMove -= panel3_MouseMove;
m_draw.MouseUpData(e.X, e.Y);
}
}
////// 鼠标移动
/// //////private void panel3_MouseMove(object sender, MouseEventArgs e)
{
m_draw.DrawingCad(e.X, e.Y);
}
////// 清空
/// //////private void toolStripMenuItem4_Click(object sender, EventArgs e)
{
m_draw.ClearAll();
}
////// Esc结束绘制
/// //////private void DrawForm_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)27)
{
this.panel3.Cursor = Cursors.Default;
this.panel3.MouseDown -= panel3_MouseDown;
this.panel3.MouseUp -= panel3_MouseUp;
this.panel3.MouseMove -= panel3_MouseMove;
if (drawIng == 2)
{
drawIng = 0;
m_draw.CloseDraw();
}
}
}
}
}绘图类代码
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace HuiTu
{
class Draw
{
//画笔、画布
Pen pen;
Graphics graphics;
//绘图类型
float type;
//图形数据
ListdrawData;
////// 初始化
/// ///画布public Draw(Graphics graphics)
{
this.graphics = graphics;
pen = new Pen(Color.Black, 1);
drawData = new List{ };
}
////// 初始化
/// ///画布///画笔颜色///画笔宽度public Draw(Graphics graphics,Color color, float width)
{
this.graphics = graphics;
pen = new Pen(color, width);
drawData = new List{ };
}
////// 设置绘图类型
/// ///绘图类型：0线，1矩形，2圆形public void SetType(float type)
{
this.type = type;
}
////// 全局数据绘制
/// private void FullDrawing()
{
try
{
foreach (var item in drawData)
{
switch (item[0])
{
case 0:
graphics.DrawLine(pen, item[1], item[2], item[3], item[4]);
break;
case 1:
float px, py, width, height;
px = Math.Min(item[1], item[3]);
py = Math.Min(item[2], item[4]);
width = Math.Abs(item[1] - item[3]);
height = Math.Abs(item[2] - item[4]);
graphics.DrawRectangle(pen, px, py, width, height);
break;
case 2:
float r, rx, ry, rw, rh;
r = (float)Math.Sqrt((item[1] - item[3]) * (item[1] - item[3]) + (item[2] - item[4]) * (item[2] - item[4]));
rx = item[1] - r;
ry = item[2] - r;
rw = r + r;
rh = r + r;
graphics.DrawEllipse(pen, rx, ry, rw, rh);
break;
default:
MessageBox.Show("数据有误！", "警告");
break;
}
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
////// 草图数据绘制
/// //////public void DrawingCad(float x, float y)
{
try
{
graphics.Clear(Color.White);
FullDrawing();
float[] cadPos = drawData.Last();
switch (cadPos[0])
{
case 0:
graphics.DrawLine(pen, cadPos[1], cadPos[2], x, y);
break;
case 1:
float px, py, width, height;
px = Math.Min(cadPos[1], x);
py = Math.Min(cadPos[2], y);
width = Math.Abs(cadPos[1] - x);
height = Math.Abs(cadPos[2] - y);
graphics.DrawRectangle(pen, px, py, width, height);
break;
case 2:
float r, rx, ry, rw, rh;
r = (float)Math.Sqrt((cadPos[1] - x) * (cadPos[1] - x) + (cadPos[2] - y) * (cadPos[2] - y));
rx = cadPos[1] - r;
ry = cadPos[2] - r;
rw = r + r;
rh = r + r;
graphics.DrawLine(pen, cadPos[1], cadPos[2], x, y);
graphics.DrawEllipse(pen, rx, ry, rw, rh);
break;
default:
MessageBox.Show("数据有误！", "警告");
break;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
////// 鼠标按下数据记录
/// ///X坐标///Y坐标public void MouseDownData(float x, float y)
{
drawData.Add(new float[] { type, x, y, x, y });
}
////// 鼠标抬起数据记录
/// ///X坐标///Y坐标public void MouseUpData(float x, float y)
{
drawData.Last()[3] = x;
drawData.Last()[4] = y;
//全局重绘
graphics.Clear(Color.White);
FullDrawing();
}
////// 清空画布
/// public void ClearAll()
{
graphics.Clear(Color.White);
drawData.Clear();
}
////// 结束绘制
/// public void CloseDraw()
{
//删除最后一条记录
drawData.RemoveAt(drawData.Count - 1);
//全局重绘
graphics.Clear(Color.White);
FullDrawing();
}
}
} 其中的逻辑关系比较简单，就不详细解释了，结束。
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