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 = 2, 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 = 2, Start = new Point(0, 0), End = new Point(0, 0) };

/// <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 > 0)
{
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 > 10)
{
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 - 1; i >= 0; i--)
{
HLine line = lineHistory[i];
bool flag = false;
foreach (Point p1 in line.PointList)
{
double distance = GetDistance(p0, p1);
if (Math.Abs(distance) < 6)
{
//需要删除
flag = true;
break;
}

}
if (flag)
{
lineHistory.RemoveAt(i);
}
}
//擦除矩形
for (int i = rectHistory.Count - 1; i >= 0; 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), 2) + Math.Pow((p0.Y - p1.Y), 2));
}

#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(0, 0);
this.CurRect.End = new Point(0, 0);
}
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 = 2;
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 = 6;
this.DrawTypes = DrawType.Line;
this.Cursor = new Cursor(global::ScreenShot.Properties.Resources.lightpen.GetHicon());
this.CurLine.LineColor = Color.FromArgb(100, Color.Yellow);
}

public void SetRectangle()
{
this.StartDraw = true;
this.CurRect.LineWidth = 3;
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。