程式狂想曲

最近在工作上需要 用到 可移動的直線  與 可 改變的圓

網路上很多介紹可以用 API 畫，但我真的不想用  gdi32

也都沒找到 相關的介紹 或 範例，只好自己想辦法寫了一個

整體的演算法

建立一個可移動的小框（做直線兩端選取用）

兩個小框中心畫一直線

點選小框時，可移動，同時重繪 小框 與 直線

需先引用

System.Drawing

System.Drawing.Drawing2D

會使用到的技巧   GraphicPath

首先建立一個  小框的 Class

        /// <summary>
        /// 會移動的方框
        /// </summary>
        public class MovePoint
        {
            public Point p;                 //紀錄方框中心的位置
            public Rectangle rect;          //依中心位置要畫出的筐
            //-----------------------------------------------------------------------------------------------------------------------------

            public Rectangle Rect
            {
                get { return rect;}
                set  { rect = value;}
            }
            
            /// <summary>
            /// 當移動方框十  方框位置重定
            /// </summary>
            /// <param name="p"></param>
            public MovePoint(Point p)
            {
                this.p = p;
                rect = new Rectangle(p.X - 3, p.Y - 3, 6, 6);
            }

            //-----------------------------------------------------------------------------------------------------------------------------
            /// <summary>
            /// 確定是否被選到
            /// </summary>
            /// <param name="e"></param>
            /// <returns></returns>
            public bool CheckSelect(Point e)
            {
              
                if (rect.Contains(e))
                    return true;
                else
                    return false;
            }

            //-----------------------------------------------------------------------------------------------------------------------------
            /// <summary>
            /// 移動時重繪
            /// </summary>
            /// <param name="e"></param>
            public void move(Point e)
            {
                this.p = e;
                rect = new Rectangle(p.X - 3, p.Y - 3, 6, 6);
            }

        }

然後在 Form 上建立一個 Picturebox   (個人喜歡用 Bitmap 繪圖)

然後在 Picturebox 上建立   Mouse_Down  Mouse_up Mouse_Move 事件

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        Bitmap bm;
        Graphics g;
        GraphicsPath gp;

        int mp_select = -1;                   //選擇方框的指標
        bool dragging = false;                //是否拖曳

        Pen pen1 = new Pen(Color.Blue , 1);       //化方框的筆

        List<CDraw.MovePoint> mp = new List<CDraw.MovePoint>();    //儲存方框的List
        //===================================================================================================================================

        private void Form1_Load(object sender, EventArgs e)
        {

            //一啟動 就在上面先畫出 直線與兩個小框
            bm = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            g = Graphics.FromImage(bm);
            gp = new GraphicsPath();

            CDraw.MovePoint MoveP;

            MoveP = new CDraw.MovePoint(new Point(10, 100));       //第一個方框的中心，新建立時會自動設定大小
            mp.Add(MoveP);

            MoveP = new CDraw.MovePoint(new Point(400, 100));       //第一個方框的中心，新建立時會自動設定大小
            mp.Add(MoveP);


            gp.AddLine(mp[0].p, mp[1].p);                           //兩個方框中新 畫出一直線

            gp.AddRectangle(mp[0].Rect);                          //將方框加入
            gp.AddRectangle(mp[1].Rect);

            g.DrawPath(pen1, gp);                                     //將  GraphicPath 畫在畫布
            pictureBox1.BackgroundImage = bm;
        }

        //===================================================================================================================================
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            for (int i = 0; i < 2; i++)
            {
                if (mp[i].CheckSelect(e.Location))
                {  //檢查點選位置是否在某個小框
                    mp_select = i;                  //選到的小框編號
                    dragging = true;              //有選到  可以拖曳
                    break;
                }

            }

        }
        //===================================================================================================================================

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            dragging = false;
        }
        //===================================================================================================================================

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {

            if (dragging)
            {
                mp[mp_select].move(e.Location);


                bm = new Bitmap(pictureBox1.Width, pictureBox1.Height);
                g = Graphics.FromImage(bm);
                gp.Reset();

                gp.AddLine(mp[0].p, mp[1].p);
          

                foreach (CDraw.MovePoint mpp in mp)
                {
                    gp.AddRectangle(mpp.Rect);
                }

                g.DrawPath(pen1, gp);
                pictureBox1.BackgroundImage = bm;

            }


        }
 


    }

程式啟動

改變線的位置 與 長短