模拟GDI+中的坐标系转换

附：转换类源代码

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TestDraw
{
    class MyTransform
    {
        private MyMatrix M = new MyMatrix();    //当前的转换矩阵
        //平移
        public void Translate(float dx, float dy)
        {
            float[,] K = {
                {1,0,dx},
                {0,1,dy},
                {0,0,1}
            };
            this.M = this.M.IR(new MyMatrix(K));
        }
        //缩放
        public void Scale(float sx, float sy)
        {
            float[,] K = {
                             {sx, 0, 0},
                             {0, sy, 0},
                             {0, 0, 1}
                         };
            this.M = this.M.IR(new MyMatrix(K));
        }
        //旋转
        public void Rotate(float sita)
        {
            float[,] K = {
                             {(float)Math.Cos(sita), -(float)Math.Sin(sita), 0},
                             {(float)Math.Sin(sita), (float)Math.Cos(sita), 0},
                             {0,0,1}
                         };
            this.M = this.M.IR(new MyMatrix(K));
        }

        //重置转换矩阵
        public void Rest()
        {
            this.M = new MyMatrix();
        }
        
        //计算新坐标
        public PointF CalculatePoint(PointF jmP)
        {
            MyPoint newP = this.M.IR(new MyPoint(jmP.X, jmP.Y));
            return new PointF(newP.P[0], newP.P[1]);
        }
        private MyPoint CalculatePoint(MyPoint jmP)
        {
            return this.M.IR(jmP);
        }  
    }

    //点矩阵
    class MyPoint
    {
        public Single[] P = {0,0,1};
        public MyPoint(float x, float y)
        {
            P[0] = x;
            P[1] = y;
        }
        
    }
    //转换矩阵
    class MyMatrix
    {
        public Single[,] K = {
                            {1,0,0},
                            {0,1,0},
                            {0,0,1}
                        };
        public MyMatrix()
        {

        }
        public MyMatrix(Single[,] K)
        {
            for (int i = 0; i < 3; i++)
            {
                for (int j = 0; j < 3; j++)
                {
                    this.K[i,j] = K[i,j];
                }
            }
        }
        //本矩阵 x R
        public MyMatrix IR(MyMatrix R)
        {
            Single[,] result = new float[3, 3];
            for (int i = 0; i < 3; i++)
            {
                for (int j = 0; j < 3; j++)
                {
                    result[i, j] = this.K[i, 0] * R.K[0, j] + this.K[i, 1] * R.K[1, j] + this.K[i, 2] * R.K[2, j];
                }
            }
            return new MyMatrix(result);
        }
        //本矩阵 x P
        public MyPoint IR(MyPoint P)
        {
            Single[] result = new float[3];
            for (int i = 0; i < 3; i++)
            {
                result[i] = this.K[i, 0] * P.P[0] + this.K[i, 1] * P.P[1] + this.K[i, 2] * P.P[2];
            }
            return new MyPoint(result[0], result[1]);
        }

        //L x 本矩阵
        public MyMatrix LI(MyMatrix L)
        {
            return L.IR(this);
        }
    }
}

测试源代码：

using System.Drawing;
using System.Windows.Forms;

namespace TestDraw
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private MyTransform transform = new MyTransform();
        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            //建模坐标系中四个点
            PointF p1 = new PointF(0, 0);
            PointF p2 = new PointF(5, 0);
            PointF p3 = new PointF(5, 2);
            PointF p4 = new PointF(0, 2);

            ////绘图坐标系向建模坐标系转变
            //transform.Translate(100, 100);
            //transform.Scale(1, -1);
            //transform.Scale(10, 10);
            //transform.Rotate((float)(3.14 / 6.0));

            ////计算点在绘图坐标系中的坐标
            //PointF np1 = transform.CalculatePoint(p1);
            //PointF np2 = transform.CalculatePoint(p2);
            //PointF np3 = transform.CalculatePoint(p3);
            //PointF np4 = transform.CalculatePoint(p4);

            ////绘制矩形
            //g.DrawLines(Pens.Red, new PointF[]{np1, np2, np3, np4, np1});

            //transform.Rest();

            g.TranslateTransform(100, 100);
            g.ScaleTransform(1, -1);
            g.ScaleTransform(10, 10);
            g.RotateTransform(30);

            g.DrawLines(new Pen(Color.Red, 1/10), new PointF[] { p1, p2, p3, p4, p1 });

            g.ResetTransform();
        }
    }
}