Csharp/CSharp Tutorial/2D/Region

Create an irregular Region add a circle to the region

using System;
using System.Collections.Generic;
using System.ruponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;
public class Form1 : Form {
    protected override void OnPaint(PaintEventArgs e) {
        Graphics g = e.Graphics;
        g.FillRectangle(Brushes.White, this.ClientRectangle);
        Region reg = new Region();
        reg.MakeEmpty();
        GraphicsPath gp = new GraphicsPath();
        gp.AddEllipse(10, 10, 50, 50);
        reg.Union(gp);
        gp.Reset();
        gp.AddLine(40, 40, 70, 10);
        gp.AddLine(70, 10, 100, 40);
        gp.CloseFigure();
        reg.Union(gp);
        reg.Union(new Rectangle(40, 50, 60, 60));
        g.SetClip(reg, CombineMode.Replace);
        g.FillRectangle(Brushes.Green, this.ClientRectangle);
        gp.Dispose();
        reg.Dispose();
    }
    public static void Main() {
        Application.Run(new Form1());
    }
}

Create a Region object, cut a rectangular hole in it, and fill it

using System;
using System.Collections.Generic;
using System.ruponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;
public class Form1 : Form {
    protected override void OnPaint(PaintEventArgs e) {
    Graphics g = e.Graphics;
    g.FillRectangle(Brushes.White, this.ClientRectangle);
    Region r = new Region(new Rectangle(30, 30, 30, 60));
    r.Exclude(new Rectangle(40, 40, 10, 10));
    g.FillRegion(Brushes.Orange, r);
    Console.WriteLine("This Region: ");
    Console.WriteLine(r.IsInfinite(g) ? " - is infinite" : " - is finite");
    Console.WriteLine(r.IsEmpty(g) ? " - is empty" : " - is non-empty");
    PointF pf = new PointF(35.0f, 30.0f);
    Console.WriteLine((r.IsVisible(pf) ? " - includes" : " - excludes") + " the point (35.0, 50.0)");
    Rectangle rect = new Rectangle(25, 65, 15, 15);
    g.DrawRectangle(Pens.Black, rect);
    Console.WriteLine((r.IsVisible(rect) ? " - is visible" : " - is invisible") + " in the rectangle shown");
    r.Dispose();
    }
    public static void Main() {
        Application.Run(new Form1());
    }
}

Create a Region whose boundary is the above GraphicsPath

using System;
using System.Collections.Generic;
using System.ruponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;
public class Form1 : Form {
    protected override void OnPaint(PaintEventArgs e) {
    Graphics g = e.Graphics;
    g.FillRectangle(Brushes.White, this.ClientRectangle);
    GraphicsPath gp = new GraphicsPath();
    gp.AddLine(10, 10, 10, 50);
    gp.AddLine(10, 50, 50, 50);
    gp.AddLine(50, 50, 50, 10);
    gp.StartFigure();
    gp.AddLine(60, 10, 60, 50);
    gp.AddLine(60, 50, 100, 50);
    gp.AddLine(100, 50, 100, 10);
    gp.CloseFigure();
    Rectangle r = new Rectangle(110, 10, 40, 40);
    gp.AddEllipse(r);
    Region reg = new Region(gp);
    g.FillRegion(Brushes.Green, reg);
    reg.Dispose();
    gp.Dispose();
    }
    public static void Main() {
        Application.Run(new Form1());
    }
}

Region.IsVisible

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Drawing.Drawing2D;
public class Form1 : System.Windows.Forms.Form {
    private System.Windows.Forms.Label label1;
    GraphicsPath gP;
    string mes = "Move to the big I!";
    FontFamily fF = new FontFamily("Times new roman");
    public Form1() {
        this.label1 = new System.Windows.Forms.Label();
        this.SuspendLayout();
        this.label1.Location = new System.Drawing.Point(88, 16);
        this.label1.Size = new System.Drawing.Size(160, 23);
        this.label1.Text = "label1";
        this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
        this.ClientSize = new System.Drawing.Size(292, 109);
        this.Controls.AddRange(new System.Windows.Forms.Control[] { this.label1 });
        this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseMove);
        this.ResumeLayout(false);
        Graphics g = this.CreateGraphics();
        label1.Text = mes;
        string s = "I";
        int fSt = (int)FontStyle.Regular;
        Point xy = new Point(50, 10);
        StringFormat sFr = StringFormat.GenericDefault;
        gP = new GraphicsPath();
        gP.AddString(s, fF, fSt, 50, xy, sFr);
    }
    [STAThread]
    static void Main() {
        Application.Run(new Form1());
    }
    protected override void OnPaint(System.Windows.Forms.PaintEventArgs e) {
        Graphics g = this.CreateGraphics();
        g.DrawPath(Pens.Black, gP);  // draw the path to the surface
        g.Dispose();
    }
    private void Form1_MouseMove(object sender, MouseEventArgs e) {
        Region reg = new Region(gP);
        if (reg.IsVisible(new Point(e.X, e.Y)))
            mes = "in";
        else
            mes = "Move to the big I!";
    }
}