Winform GDI+ 绘图

1. 常用结构

1) Point：点坐标

2) Size：大小

3) Rectangle：包括位置与大小

Rectangle.Location:位置坐标

Rectangle.Size：大小

4) Pen：画笔

红色笔:Pens.Red,黑色笔：Pens.Black

其它的一次类推。

5) Brush：画刷

红色画刷：Brushes.Red 黑色画刷：Brushes.Black

其它以此类推。

2. 坐标变换

对象	屏幕坐标转化为客户区坐标	客户区坐标转化为屏幕坐标
Point	PointToClinet(Point pt)	PointToScreen(Point pt)
Rectangle	RectangleToClient	RectangleToScreen

涉及坐标的程序必须先考虑是否需要坐标变换

坐标平移：

X目标=X现在+dx

Y目标=Y现在+dy

坐标缩放：

X目标=X现在*dx

Y目标=Y现在*dy

坐标旋转：

X目标=X现在*Cos（α）+Y现在*Sin（α）

Y目标= X现在*Sin（α）+Y现在*Cos（α）

综合后

引入矩阵

综合后的公式可以写为

坐标变换会因为顺序的不同而产生不同的结果，多次坐标变换的结果是多个矩阵相乘。

右下角矩阵说明

X	Y	隐含列
Sx 缩放因子	Ry旋转因子	0
Rx旋转因子	sy缩放因子	0
Dx平移因子	Dy平移因子	1

图-1 原始矩阵

图-2 x轴平移100个像素

图-3 y轴平移100个像素

图-4 x轴放大1.5倍

图-5 y轴放大1.5倍

图-6 x轴旋转0.5

图-7 y轴旋转0.5

3. 鼠标事件

事件名称	说明
OnMouseUp	鼠标松开
OnMouseDown	鼠标按下
OnMouseMove	鼠标移动
OnMouseEnter	鼠标进入
OnMouseLeave	鼠标离开
OnMouseHover	鼠标停留。Hover事件至多在Enter与Leave之间发生一次
OnMouseCaptureChanged	鼠标捕获变化，捕获发生一次，释放发生一次

4. 常见问题与解决方法

1) 如判断鼠标按下拖动

首先在鼠标的OnMouseMoveMove事件中添加如下判断：

if (e.Button == MouseButtons.Left)

{

//鼠标移动的过程中是否按下了左键

}

2) 如何避免鼠标按住旋转后划线后出现多条痕迹

在OnPaint事件中添加如下代码：

//划线之前先用背景色把原先的痕迹抹掉。

g.Clear(this.BackColor);

3) 鼠标的Capture事件

鼠标的捕获释放只能在一个控件中完成，前一个控件A捕获了鼠标后，不可能由下一个控件B捕获，必须是A释放了之后才能由B控件捕获。

假设在A控件上按住鼠标移动，鼠标移出A放在了B控件上。假设在B控件中的OnMouseHover中添加了代码弹出对话框，这样的对话框不会弹出，因为A捕获了鼠标，在A未释放之前，其他控件不可能激发鼠标相关的事件，除非其他控件捕获它之后，才可能激发它的事件。

附坐标变化程序代码：

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 GDITransformApp
{
    
    public partial class Transform1 : Form
    {
        public class MyMatrix
        {
            public float X
            {
                get;
                set;
            }
            public float Y
            {
                get;
                set;
            }

            public MyMatrix(float x, float y)
            {
                X = x;
                Y = y;
            }

        }

        #region Coordanate
        //坐标轴X与控件边缘的距离
        private const int xPad = 80;

        //坐标轴Y与控件边缘的距离
        private const int yPad = 60;

        /// <summary>
        /// X坐标标签间距
        /// </summary>
        private int coordinateLablePadX = 20;
        public int CoordinateLablePadX
        {
            get
            {
                return coordinateLablePadX;
            }

            set
            {
                Invalidate();
                coordinateLablePadX = value;
            }
        }


        /// <summary>
        /// Y坐标标签间距
        /// </summary>
        private int coordinateLablePadY = 30;
        public int CoordinateLablePadY
        {
            get
            {
                return coordinateLablePadY;
            }

            set
            {
                Invalidate();
                coordinateLablePadY = value;
            }
        }

        /// <summary>
        /// y坐标轴起点坐标
        /// </summary>
        public Point YCoordinateStartPoint
        {
            get
            {
                return new Point(xPad, this.Height - yPad);

            }
        }


        /// <summary>
        ///  y坐标轴终点坐标
        /// </summary>
        public Point YCoordinateEndPoint
        {
            get
            {
                return new Point(xPad, yPad);
            }
        }


        /// <summary>
        ///  x坐标轴起点坐标
        /// </summary>
        public Point XCoordinateStartPoint
        {
            get
            {
                return YCoordinateStartPoint;
            }
        }

        /// <summary>
        ///  x坐标轴终点坐标
        /// </summary>
        public Point XCoordinateEndPoint
        {
            get
            {
                Point current = new Point();
                current.X = Width - xPad;
                current.Y = Height - yPad;
                return current;
            }
        }

        private void DrawCoordinate(PaintEventArgs e)
        {


            Pen currentPen = new Pen(Color.Black);

            currentPen.EndCap = LineCap.ArrowAnchor;

            //绘制Y轴
            e.Graphics.DrawLine(
                currentPen,
                YCoordinateStartPoint,
                YCoordinateEndPoint
                );

            //绘制Y轴
            e.Graphics.DrawLine(
                currentPen,
                XCoordinateStartPoint,
                XCoordinateEndPoint
                );
            currentPen.Dispose();

            //绘制X,Y 标签
            DrawCoordinateLabel(e.Graphics, YCoordinateStartPoint, YCoordinateEndPoint, XCoordinateStartPoint, XCoordinateEndPoint);
        }

        /// <summary>
        /// 绘制坐标标记
        /// </summary>
        private void DrawCoordinateLabel(Graphics gp, Point startYPoint, Point endYPoint, Point startXPoint, Point endXPoint)
        {
            //int y = YCoordinateStartPoint  .Y -  YCoordinateEndPoint.Y;

            int currentValue = -1;
            float labelX = 0, labelY = 0;
            int pad = 5;

            //绘制Y轴
            for (int current = YCoordinateStartPoint.Y; current > YCoordinateEndPoint.Y; current -= CoordinateLablePadY)
            {
                currentValue++;

                SizeF textSize = gp.MeasureString(currentValue.ToString(), Font);

                labelX = YCoordinateStartPoint.X - xPad / 2;
                labelY = current - textSize.Height / 2;

                //绘制label
                gp.DrawString(currentValue.ToString(), Font, Brushes.Black,
                    new PointF(labelX, labelY)
                        );

                //绘制|-
                gp.DrawLine(Pens.Black, new Point(YCoordinateStartPoint.X, current), new Point(YCoordinateStartPoint.X + pad, current));

            }

            currentValue = -1;
            //绘制X轴
            for (int current = XCoordinateStartPoint.X; current < XCoordinateEndPoint.X; current += CoordinateLablePadX)
            {
                currentValue++;

                SizeF textSize = gp.MeasureString(currentValue.ToString(), Font);

                labelY = XCoordinateStartPoint.Y + yPad / 2;
                labelX = current;

                //绘制label
                gp.DrawString(currentValue.ToString(), Font, Brushes.Black,
                    new PointF(labelX, labelY)
                        );

                //绘制_|_
                gp.DrawLine(Pens.Black,
                    new Point(current, XCoordinateStartPoint.Y),
                new Point(current, XCoordinateStartPoint.Y - pad)
                );


            }




        }

#endregion

        float angle = 0f;
        float scaleX = 1f;
        float scaleY = 1f;

        float translateX = 1f;
        float translateY = 1f;
        public Transform1()
        {
            InitializeComponent();
        }

        Matrix matrix = new Matrix();

        List<MyMatrix> myList = new List<MyMatrix>();


       

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            e.Graphics.Clear(this.BackColor);

            DrawCoordinate(e);

            DrawRectangle();

        }

        private void DrawRectangle()
        {
            using (Graphics gh = CreateGraphics())
            {
               
                Rectangle rect = new Rectangle(100, 100, 200, 200);
                
                StringFormat sf=new StringFormat();
                sf.Alignment=StringAlignment.Center ;
                sf.LineAlignment=StringAlignment .Center ;

                //平移
                gh.TranslateTransform(translateX, translateY);
                //旋转
                gh.RotateTransform(angle);
                //缩放
                gh.ScaleTransform(scaleX, scaleY);

                //设置gh的变换矩阵
                gh.Transform = matrix;
              
                gh.DrawRectangle(Pens.Red, rect);
                gh.DrawString("AAAAAAAAA", this.Font, Brushes.Blue, rect, sf);

                matrix = gh.Transform;

                myList.Add(new MyMatrix(matrix.Elements[0], matrix.Elements[1]));
                myList.Add(new MyMatrix(matrix.Elements[2], matrix.Elements[3]));
                myList.Add(new MyMatrix(matrix.Elements[4], matrix.Elements[5]));

                this.dgvMatrix.DataSource = myList;
          
                
            }

        }

        private void button1_Click(object sender, EventArgs e)
        {
            angle += 10;
            this.Invalidate();
        }

        private void btnScaleAdd_Click(object sender, EventArgs e)
        {
            scaleX += 1;
            scaleY += 1;
            this.Invalidate();
        }

        private void btnScaleSub_Click(object sender, EventArgs e)
        {
            scaleX -= 1;
            scaleY -= 1;
            this.Invalidate();
        }

        private void btnRolateSub_Click(object sender, EventArgs e)
        {
            angle -= 10;
            this.Invalidate();
        }

        private void btnBack_Click(object sender, EventArgs e)
        {
            angle = 0f;
            scaleX = 1f;
            scaleY = 1f;
            translateX = 0f;
            translateY = 0f;
            this.Invalidate();
        }

        private void btnTranslateAdd_Click(object sender, EventArgs e)
        {
            translateX += 3f;
            translateY += 3f;
            this.Invalidate();
        }

        private void btnTranslateSub_Click(object sender, EventArgs e)
        {
            translateX -= 5f;
            translateY -= 5f;
            this.Invalidate();
        }

       

        private void btnMatrixBack_Click(object sender, EventArgs e)
        {
            matrix = new Matrix
            (
              1,0,
              0,1,
              0,0
            );
            this.Invalidate();
        }

        private void button1_Click_1(object sender, EventArgs e)
        {
            matrix = new Matrix(

               ((MyMatrix)this.dgvMatrix.Rows[0].DataBoundItem).X, ((MyMatrix)this.dgvMatrix.Rows[0].DataBoundItem).Y ,
               ((MyMatrix)this.dgvMatrix.Rows[1].DataBoundItem).X, ((MyMatrix)this.dgvMatrix.Rows[1].DataBoundItem).Y ,
               ((MyMatrix)this.dgvMatrix.Rows[2].DataBoundItem).X, ((MyMatrix)this.dgvMatrix.Rows[2].DataBoundItem).Y 
               );
            
            this.Invalidate();

        }
    }
}