1 坐标系统

(1) 坐标原点：在窗体或控件的左上角，坐标为(0,0)

(2) 正方向：X轴正方向为水平向右，Y轴正方向为竖直向下

(3) 单位：在设置时，一般以像素为单位，像素(Pixel)是由图像(Picture)和元素(Element)组成，是用来计算数码影像的一种单位。

把影像放大数倍，会发现这些连续的色调其实是有许多色彩相近的小方点组成，这些小方点是构成影像的最小单位—像素。

图形的质量是有像素决定，像素越大，分辨率也越大。

2 命名空间 --- System.Drawing

(1) System.Drawing 提供了对GDI+基本图形功能的访问

(2)  System.Drawing 常用基本类及结构

3 Graphics类

Graphics类封装了一个GDI+绘制界面，提供将对象绘制到显示界面的方法。使用GDI+创建图形图像时，需要先创建Graphics对象，即在哪里画图。

共有3种类型的绘图界面：

（1）   窗体和控件

（2）   打印机

（3）   内存的位图

创建图形对象的3中方法：

（1）控件类的OnPaint()方法参数PaintEventArgs获取Graphics对象

（2）窗体类或控件类中的CreateGraphics()方法获得Graphics对象

（3）从位图对象(Bitmap)产生一个Graphics对象

Graphics类的常用方法

4 绘图工具类

5 Brush类的派生类

6 案例  免费下载地址 http://download.csdn.net/detail/taoerit/8350869

7  代码

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 GDI绘图
{
    public partial class MainDialog : Form
    {
        public MainDialog()
        {
            InitializeComponent();
        }

        private void MainDialog_Load(object sender, EventArgs e)
        {

        }

        private void lineButton_Click(object sender, EventArgs e)
        {
            // 画直线
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red);
            pen.Width = 2;
            Point startPoint = new Point(20,20);
            Point endPoint = new Point(70,20);
            gra.DrawLine(pen,startPoint,endPoint);
            
            pen.Dispose();
            gra.Dispose();
        }

        private void rectangleButton_Click(object sender, EventArgs e)
        {
            //画矩形
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red);
            gra.DrawRectangle(pen, 20,50, 100,100);
            pen.Dispose();
            gra.Dispose();
        }
        private void cyliderButton_Click(object sender, EventArgs e)
        {
            //圆柱体,有许多个椭圆有底部逐渐叠起来的，最后填充颜色

            int height = this.ClientSize.Height - 150;
            int width = this.ClientSize.Width - 50;
            int vHeight = 200;
            int vWidth = 100;
            Graphics gra = this.CreateGraphics();
            gra.Clear(Color.White);
            Pen pen = new Pen(Color.Gray,2);
            SolidBrush brush = new SolidBrush(Color.Gainsboro);

            for (int i = height / 2; i > 0;i-- )
            {
                gra.DrawEllipse(pen,width/2,i,vHeight,vWidth);
            }

            gra.FillEllipse(brush,width/2,0,vHeight,vWidth);
        }

        private void fillRectangleButton_Click(object sender, EventArgs e)
        {
            //画矩形
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red,3);
            Brush brush = pen.Brush;
            Rectangle rect = new Rectangle(20,50,100,100);
            gra.FillRectangle(brush,rect);
            gra.Dispose();
        }

        private void drawEllispeButton_Click(object sender, EventArgs e)
        {
            Graphics gra = this.CreateGraphics();
            Rectangle rect = new Rectangle(0,0,200,100);
            LinearGradientBrush brush = new LinearGradientBrush(rect,Color.Orange,Color.Purple,90);
            gra.FillEllipse(brush,rect);
            gra.Dispose();
        }

        private void fontButton_Click(object sender, EventArgs e)
        {
            Graphics gra = this.CreateGraphics();
            Font font = new Font("隶书",24,FontStyle.Italic);
            Pen pen = new Pen(Color.Blue,3);
            gra.DrawString("Windows应用程序设计",font,pen.Brush,10,100);
        }

        private void ellispeButton_Click(object sender, EventArgs e)
        {
            // 画圆形
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red);
            gra.DrawEllipse(pen, 0, 0, 200,100);
            pen.Dispose();
            gra.Dispose();
        }

        private void moveEllispeButton_Click(object sender, EventArgs e)
        {
            // 移动圆形
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red);
            gra.TranslateTransform(10,10);// 改变起坐标(10,10)
            gra.DrawEllipse(pen, 0, 0, 200, 100);

            gra.Dispose();
        }

        private void scaleEllispeButton_Click(object sender, EventArgs e)
        {
            // 缩放圆形
            float xScale = 1.5F;
            float yScale = 2F;
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Red);
            gra.ScaleTransform(xScale, yScale);// X轴放大1.5倍， Y轴放大2倍
            gra.DrawEllipse(pen, 0, 0, 200, 100);
            gra.Dispose();
        }

        private void curveButton_Click(object sender, EventArgs e)
        {
            //绘制曲线
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Blue,3);
            Point oo1 = new Point(30,this.ClientSize.Height -100);
            Point oo2 = new Point(this.ClientSize.Width - 50 ,this.ClientSize.Height - 100);
            gra.DrawLine(pen,oo1,oo2);
            Point oo3 = new Point(30, 30);
            gra.DrawLine(pen, oo1, oo3);
            Font font = new System.Drawing.Font("宋体",12,FontStyle.Bold);
            gra.DrawString("X",font,pen.Brush,oo2);
            gra.DrawString("Y", font,pen.Brush,10,10);

            int x1 = 0, x2 = 0;
            double a = 0;
            double y1 = 0, y2 = this.ClientSize.Height - 100;
            for (x2 = 0; x2 < this.ClientSize.Width;x2++ )
            {
                a = 2 * Math.PI * x2 / (this.ClientSize.Width);
                y2 = Math.Sin(a);
                y2 = (1 - y2) *(this.ClientSize.Height-100)/2;
                gra.DrawLine(pen,x1 +30,(float)y1 ,x2+30,(float)y2);
                x1 = x2;
                y1 = y2;
            }
            gra.Dispose();
        }

        private void piechartButton_Click(object sender, EventArgs e)
        {
            //饼图
            Graphics gra = this.CreateGraphics();
            Pen pen = new Pen(Color.Blue, 3);
            Rectangle rect = new Rectangle(50,50,200,100);
            Brush brush = new SolidBrush(Color.Blue);
            gra.FillPie(pen.Brush,rect,0,60);
            gra.FillPie(brush,rect,60,150);
            brush = new SolidBrush(Color.Yellow);
            gra.FillPie(brush,rect,210,150);

        }

    }
}

C# GDI+ 绘图