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：

 

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();

        }
    }
}