C# - VS2019通过重写pictureBox实现简单的桌面截图功能

前言

通过创建客制化组件（继承pictureBox），新增属性和构造方法，实现屏幕截图时需要用到的功能点。再通过监控鼠标按下、移动和释放，来获取起始点区域。最后通过操作BMP图像，实现截图的新增、修改和保存功能。

核心点

• 组件的创建（重写）
• 鼠标监控事件
• BMP图像重绘

核心代码

     /// <summary>
     /// 重写图片控件
     /// </summary>
     [Serializable]
     public partial class HexPictureBox : PictureBox
     {
         #region 属性和构造函数

         public HexPictureBox()
         {
             InitializeComponent();
         }

         private bool startDraw = false;

         public bool StartDraw
         {
             get { return startDraw; }

             set { startDraw = value; }
         }

         private List<HLine> lineHistory = new List<HLine>();

         public List<HLine> LineHistory
         {
             get { return lineHistory; }

             private set { lineHistory = value; }
         }

         private HLine curLine = new HLine() { LineColor = Color.White, LineWidth = , PointList = new List<Point>() };

         /// <summary>
         /// 当前绘制线
         /// </summary>
         public HLine CurLine
         {
             get { return curLine; }

             private set { curLine = value; }
         }

         private HRectangle curRect = new HRectangle() { LineColor = Color.White, LineWidth = , Start = new Point(, ), End = new Point(, ) };

         /// <summary>
         /// 当前需要绘制的矩形
         /// </summary>
         public HRectangle CurRect
         {
             get { return curRect; }

             set { curRect = value; }
         }

         private List<HRectangle> rectHistory = new List<HRectangle>();

         public List<HRectangle> RectHistory
         {
             get { return rectHistory; }

             private set { rectHistory = value; }
         }

         private DrawType drawTypes = DrawType.None;

         public DrawType DrawTypes
         {
             get { return drawTypes; }

             set { drawTypes = value; }
         }

         #endregion

         #region 绘制功能

         protected override void OnPaint(PaintEventArgs pe)
         {
             base.OnPaint(pe);
             Graphics g = pe.Graphics;
             DrawHistory(g);
             //绘制当前线
             if (startDraw && this.curLine.PointList != null && this.curLine.PointList.Count > )
             {
                 DrawLine(g, this.curLine);
             }
             if (startDraw && this.curRect.Start != null && this.curRect.End != null && this.curRect.Start != this.curRect.End)
             {
                 DrawRectangle(g, this.curRect);
             }
         }

         public void DrawHistory(Graphics g)
         {
             //绘制线历史记录
             if (LineHistory != null)
             {
                 foreach (HLine lh in LineHistory)
                 {
                     if (lh.PointList.Count > )
                     {
                         DrawLine(g, lh);
                     }
                 }
             }
             //绘制矩形历史记录
             if (RectHistory != null)
             {
                 foreach (HRectangle lh in RectHistory)
                 {
                     if (lh.Start != null && lh.End != null && lh.Start != lh.End)
                     {
                         DrawRectangle(g, lh);
                     }
                 }
             }
         }

         /// <summary>
         /// 绘制线
         /// </summary>
         /// <param name="g"></param>
         /// <param name="line"></param>
         private void DrawLine(Graphics g, HLine line)
         {
             g.SmoothingMode = SmoothingMode.AntiAlias;
             using (Pen p = new Pen(line.LineColor, line.LineWidth))
             {
                 //设置起止点线帽
                 p.StartCap = LineCap.Round;
                 p.EndCap = LineCap.Round;

                 //设置连续两段的联接样式
                 p.LineJoin = LineJoin.Round;
                 g.DrawCurve(p, line.PointList.ToArray()); //画平滑曲线
             }
         }

         /// <summary>
         /// 绘制矩形
         /// </summary>
         /// <param name="g"></param>
         /// <param name="rect"></param>
         private void DrawRectangle(Graphics g, HRectangle rect)
         {
             g.SmoothingMode = SmoothingMode.AntiAlias;
             using (Pen p = new Pen(rect.LineColor, rect.LineWidth))
             {
                 //设置起止点线帽
                 p.StartCap = LineCap.Round;
                 p.EndCap = LineCap.Round;

                 //设置连续两段的联接样式
                 p.LineJoin = LineJoin.Round;
                 g.DrawRectangle(p, rect.Start.X, rect.Start.Y, rect.End.X - rect.Start.X, rect.End.Y - rect.Start.Y); //画平滑曲线
             }
         }

         public void Earser(Point p0)
         {
             for (int i = lineHistory.Count - ; i >= ; i--)
             {
                 HLine line = lineHistory[i];
                 bool flag = false;
                 foreach (Point p1 in line.PointList)
                 {
                     double distance = GetDistance(p0, p1);
                     if (Math.Abs(distance) < )
                     {
                         //需要删除
                         flag = true;
                         break;
                     }

                 }
                 if (flag)
                 {
                     lineHistory.RemoveAt(i);
                 }
             }
             //擦除矩形
             for (int i = rectHistory.Count - ; i >= ; i--)
             {
                 HRectangle rect = rectHistory[i];

                 if (p0.X > rect.Start.X && p0.X < rect.End.X && p0.Y > rect.Start.Y && p0.Y < rect.End.Y)
                 {

                     rectHistory.RemoveAt(i);
                 }
             }
         }

         /// <summary>
         /// 获取两点之间的距离
         /// </summary>
         /// <param name="p0"></param>
         /// <param name="p1"></param>
         /// <returns></returns>
         private double GetDistance(Point p0, Point p1)
         {
             return Math.Sqrt(Math.Pow((p0.X - p1.X), ) + Math.Pow((p0.Y - p1.Y), ));
         }

         #endregion

         #region 鼠标事件响应

         /// <summary>
         /// 鼠标移动时设置点
         /// </summary>
         /// <param name="p"></param>
         public void SetPointAndRefresh(Point p)
         {
             if (this.drawTypes == DrawType.Line)
             {
                 this.curLine.PointList.Add(p);
             }
             if (this.drawTypes == DrawType.Rect)
             {
                 this.curRect.End = p;
             }
             this.Refresh();

         }

         public void OnMouseDown(Point p)
         {
             if (this.DrawTypes == DrawType.Line)
             {
                 this.CurLine.PointList.Clear();
                 this.CurLine.PointList.Add(p);
             }
             if (this.DrawTypes == DrawType.Rect)
             {
                 this.CurRect.Start = p;
             }
         }

         public void OnMouseUp(Point p)
         {
             if (this.DrawTypes == DrawType.Line)
             {
                 //右键起来时，停止绘图，并写入历史记录
                 Point[] pCopy = this.CurLine.PointList.ToArray();
                 List<Point> lstPoint = new List<Point>();
                 lstPoint.AddRange(pCopy);
                 this.LineHistory.Add(new HLine() { LineColor = this.CurLine.LineColor, LineWidth = this.CurLine.LineWidth, PointList = lstPoint });
                 this.CurLine.PointList.Clear();
             }
             if (this.DrawTypes == DrawType.Rect)
             {
                 this.RectHistory.Add(new HRectangle() { LineColor = this.CurRect.LineColor, LineWidth = this.CurRect.LineWidth, Start = this.CurRect.Start, End = this.CurRect.End });
                 this.CurRect.Start = new Point(, );
                 this.CurRect.End = new Point(, );
             }
             if (this.DrawTypes == DrawType.Earser)
             {
                 //如果是橡皮擦功能
                 this.Earser(p);
                 this.Refresh();
             }
         }

         #endregion

         #region 初始设置

         public void SetPen(Color c)
         {
             this.DrawTypes = DrawType.Line;
             this.CurLine.LineWidth = ;
             this.CurLine.LineColor = c;
             //通过图片的句柄获取指针
             this.Cursor = new Cursor(global::ScreenShot.Properties.Resources.pen.GetHicon());
             this.StartDraw = true;
         }

         public void SetLightPen()
         {
             this.StartDraw = true;
             this.CurLine.LineWidth = ;
             this.DrawTypes = DrawType.Line;
             this.Cursor = new Cursor(global::ScreenShot.Properties.Resources.lightpen.GetHicon());
             this.CurLine.LineColor = Color.FromArgb(, Color.Yellow);
         }

         public void SetRectangle()
         {
             this.StartDraw = true;
             this.CurRect.LineWidth = ;
             this.DrawTypes = DrawType.Rect;
             this.CurRect.LineColor = Color.Red;
             this.Cursor = Cursors.Cross;
         }

         public void SetEarser()
         {
             this.DrawTypes = DrawType.Earser;//橡皮檫
             this.Cursor = new Cursor(global::ScreenShot.Properties.Resources.easer1.GetHicon());
         }

         public void SetDefault()
         {
             this.Cursor = Cursors.Default;
             this.StartDraw = false;
         }

         #endregion
     }

实现效果

作者：Jeremy.Wu
  出处：https://www.cnblogs.com/jeremywucnblog/

  本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。