C#-Code

namespace SelfMadePaint
{
    partial class Form1
    {
        /// <summary>
        /// Erforderliche Designervariable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Verwendete Ressourcen bereinigen.
        /// </summary>
        /// <param name="disposing">True, wenn verwaltete Ressourcen gelöscht werden sollen; andernfalls False.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Vom Windows Form-Designer generierter Code

        /// <summary>
        /// Erforderliche Methode für die Designerunterstützung.
        /// Der Inhalt der Methode darf nicht mit dem Code-Editor geändert werden.
        /// </summary>
        private void InitializeComponent()
        {
            this.RedTb = new System.Windows.Forms.TextBox();
            this.GreenTb = new System.Windows.Forms.TextBox();
            this.BlueTb = new System.Windows.Forms.TextBox();
            this.vis_LbRed = new System.Windows.Forms.Label();
            this.vis_GreenLb = new System.Windows.Forms.Label();
            this.vis_BlueLb = new System.Windows.Forms.Label();
            this.vis_ColorGb = new System.Windows.Forms.GroupBox();
            this.vis_FormGb = new System.Windows.Forms.GroupBox();
            this.FormsCb = new System.Windows.Forms.ComboBox();
            this.FillCbox = new System.Windows.Forms.CheckBox();
            this.LiveCbox = new System.Windows.Forms.CheckBox();
            this.ClearBtn = new System.Windows.Forms.Button();
            this.vis_ToolboxGb = new System.Windows.Forms.GroupBox();
            this.FillPnl = new System.Windows.Forms.Panel();
            this.CursorPnl = new System.Windows.Forms.Panel();
            this.ColorPb = new System.Windows.Forms.PictureBox();
            this.DrawBoxPb = new System.Windows.Forms.PictureBox();
            this.vis_ColorGb.SuspendLayout();
            this.vis_FormGb.SuspendLayout();
            this.vis_ToolboxGb.SuspendLayout();
            ((System.ComponentModel.ISupportInitialize)(this.ColorPb)).BeginInit();
            ((System.ComponentModel.ISupportInitialize)(this.DrawBoxPb)).BeginInit();
            this.SuspendLayout();
            // 
            // RedTb
            // 
            this.RedTb.Location = new System.Drawing.Point(47, 13);
            this.RedTb.Name = "RedTb";
            this.RedTb.Size = new System.Drawing.Size(42, 20);
            this.RedTb.TabIndex = 1;
            this.RedTb.Text = "0";
            this.RedTb.TextChanged += new System.EventHandler(this.TbColorChanged);
            this.RedTb.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.TbOnlyNumbers);
            // 
            // GreenTb
            // 
            this.GreenTb.Location = new System.Drawing.Point(47, 39);
            this.GreenTb.Name = "GreenTb";
            this.GreenTb.Size = new System.Drawing.Size(42, 20);
            this.GreenTb.TabIndex = 2;
            this.GreenTb.Text = "0";
            this.GreenTb.TextChanged += new System.EventHandler(this.TbColorChanged);
            this.GreenTb.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.TbOnlyNumbers);
            // 
            // BlueTb
            // 
            this.BlueTb.Location = new System.Drawing.Point(47, 65);
            this.BlueTb.Name = "BlueTb";
            this.BlueTb.Size = new System.Drawing.Size(42, 20);
            this.BlueTb.TabIndex = 3;
            this.BlueTb.Text = "0";
            this.BlueTb.TextChanged += new System.EventHandler(this.TbColorChanged);
            this.BlueTb.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.TbOnlyNumbers);
            // 
            // vis_LbRed
            // 
            this.vis_LbRed.AutoSize = true;
            this.vis_LbRed.Location = new System.Drawing.Point(6, 16);
            this.vis_LbRed.Name = "vis_LbRed";
            this.vis_LbRed.Size = new System.Drawing.Size(27, 13);
            this.vis_LbRed.TabIndex = 4;
            this.vis_LbRed.Text = "Red";
            // 
            // vis_GreenLb
            // 
            this.vis_GreenLb.AutoSize = true;
            this.vis_GreenLb.Location = new System.Drawing.Point(6, 42);
            this.vis_GreenLb.Name = "vis_GreenLb";
            this.vis_GreenLb.Size = new System.Drawing.Size(36, 13);
            this.vis_GreenLb.TabIndex = 5;
            this.vis_GreenLb.Text = "Green";
            // 
            // vis_BlueLb
            // 
            this.vis_BlueLb.AutoSize = true;
            this.vis_BlueLb.Location = new System.Drawing.Point(6, 68);
            this.vis_BlueLb.Name = "vis_BlueLb";
            this.vis_BlueLb.Size = new System.Drawing.Size(28, 13);
            this.vis_BlueLb.TabIndex = 6;
            this.vis_BlueLb.Text = "Blue";
            // 
            // vis_ColorGb
            // 
            this.vis_ColorGb.Controls.Add(this.ColorPb);
            this.vis_ColorGb.Controls.Add(this.vis_LbRed);
            this.vis_ColorGb.Controls.Add(this.vis_BlueLb);
            this.vis_ColorGb.Controls.Add(this.RedTb);
            this.vis_ColorGb.Controls.Add(this.vis_GreenLb);
            this.vis_ColorGb.Controls.Add(this.GreenTb);
            this.vis_ColorGb.Controls.Add(this.BlueTb);
            this.vis_ColorGb.Location = new System.Drawing.Point(648, 12);
            this.vis_ColorGb.Name = "vis_ColorGb";
            this.vis_ColorGb.Size = new System.Drawing.Size(100, 121);
            this.vis_ColorGb.TabIndex = 7;
            this.vis_ColorGb.TabStop = false;
            this.vis_ColorGb.Text = "Color";
            // 
            // vis_FormGb
            // 
            this.vis_FormGb.Controls.Add(this.FillCbox);
            this.vis_FormGb.Controls.Add(this.FormsCb);
            this.vis_FormGb.Location = new System.Drawing.Point(648, 139);
            this.vis_FormGb.Name = "vis_FormGb";
            this.vis_FormGb.Size = new System.Drawing.Size(100, 76);
            this.vis_FormGb.TabIndex = 8;
            this.vis_FormGb.TabStop = false;
            this.vis_FormGb.Text = "Form";
            // 
            // FormsCb
            // 
            this.FormsCb.Location = new System.Drawing.Point(6, 19);
            this.FormsCb.Name = "FormsCb";
            this.FormsCb.Size = new System.Drawing.Size(88, 21);
            this.FormsCb.TabIndex = 0;
            this.FormsCb.SelectedIndexChanged += new System.EventHandler(this.FormsCb_SelectedIndexChanged);
            // 
            // FillCbox
            // 
            this.FillCbox.AutoSize = true;
            this.FillCbox.Location = new System.Drawing.Point(7, 46);
            this.FillCbox.Name = "FillCbox";
            this.FillCbox.Size = new System.Drawing.Size(38, 17);
            this.FillCbox.TabIndex = 1;
            this.FillCbox.Text = "Fill";
            this.FillCbox.UseVisualStyleBackColor = true;
            // 
            // LiveCbox
            // 
            this.LiveCbox.AutoSize = true;
            this.LiveCbox.Checked = true;
            this.LiveCbox.CheckState = System.Windows.Forms.CheckState.Checked;
            this.LiveCbox.Location = new System.Drawing.Point(428, 395);
            this.LiveCbox.Name = "LiveCbox";
            this.LiveCbox.Size = new System.Drawing.Size(46, 17);
            this.LiveCbox.TabIndex = 9;
            this.LiveCbox.Text = "Live";
            this.LiveCbox.UseVisualStyleBackColor = true;
            this.LiveCbox.CheckedChanged += new System.EventHandler(this.LiveCbox_CheckedChanged);
            // 
            // ClearBtn
            // 
            this.ClearBtn.Location = new System.Drawing.Point(648, 221);
            this.ClearBtn.Name = "ClearBtn";
            this.ClearBtn.Size = new System.Drawing.Size(75, 23);
            this.ClearBtn.TabIndex = 10;
            this.ClearBtn.Text = "Clear";
            this.ClearBtn.UseVisualStyleBackColor = true;
            this.ClearBtn.Click += new System.EventHandler(this.ClearBtn_Click);
            // 
            // vis_ToolboxGb
            // 
            this.vis_ToolboxGb.Controls.Add(this.FillPnl);
            this.vis_ToolboxGb.Controls.Add(this.CursorPnl);
            this.vis_ToolboxGb.Location = new System.Drawing.Point(442, 12);
            this.vis_ToolboxGb.Name = "vis_ToolboxGb";
            this.vis_ToolboxGb.Size = new System.Drawing.Size(200, 55);
            this.vis_ToolboxGb.TabIndex = 11;
            this.vis_ToolboxGb.TabStop = false;
            this.vis_ToolboxGb.Text = "Toolbox";
            // 
            // FillPnl
            // 
            this.FillPnl.BackgroundImage = global::SelfMadePaint.Properties.Resources.fill;
            this.FillPnl.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch;
            this.FillPnl.Location = new System.Drawing.Point(47, 16);
            this.FillPnl.Name = "FillPnl";
            this.FillPnl.Size = new System.Drawing.Size(25, 25);
            this.FillPnl.TabIndex = 1;
            this.FillPnl.Click += new System.EventHandler(this.FillPnl_Click);
            // 
            // CursorPnl
            // 
            this.CursorPnl.BackgroundImage = global::SelfMadePaint.Properties.Resources.cursor;
            this.CursorPnl.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Stretch;
            this.CursorPnl.Location = new System.Drawing.Point(6, 16);
            this.CursorPnl.Name = "CursorPnl";
            this.CursorPnl.Size = new System.Drawing.Size(25, 25);
            this.CursorPnl.TabIndex = 0;
            this.CursorPnl.Click += new System.EventHandler(this.CursorPnl_Click);
            // 
            // ColorPb
            // 
            this.ColorPb.Location = new System.Drawing.Point(9, 91);
            this.ColorPb.Name = "ColorPb";
            this.ColorPb.Size = new System.Drawing.Size(80, 24);
            this.ColorPb.TabIndex = 7;
            this.ColorPb.TabStop = false;
            // 
            // DrawBoxPb
            // 
            this.DrawBoxPb.BackColor = System.Drawing.Color.White;
            this.DrawBoxPb.Location = new System.Drawing.Point(12, 12);
            this.DrawBoxPb.Name = "DrawBoxPb";
            this.DrawBoxPb.Size = new System.Drawing.Size(400, 400);
            this.DrawBoxPb.TabIndex = 0;
            this.DrawBoxPb.TabStop = false;
            this.DrawBoxPb.Paint += new System.Windows.Forms.PaintEventHandler(this.DrawBoxPb_Paint);
            this.DrawBoxPb.MouseDown += new System.Windows.Forms.MouseEventHandler(this.DrawBoxPb_MouseDown);
            this.DrawBoxPb.MouseMove += new System.Windows.Forms.MouseEventHandler(this.DrawBoxPb_MouseMove);
            this.DrawBoxPb.MouseUp += new System.Windows.Forms.MouseEventHandler(this.DrawBoxPb_MouseUp);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(760, 426);
            this.Controls.Add(this.vis_ToolboxGb);
            this.Controls.Add(this.ClearBtn);
            this.Controls.Add(this.LiveCbox);
            this.Controls.Add(this.vis_FormGb);
            this.Controls.Add(this.vis_ColorGb);
            this.Controls.Add(this.DrawBoxPb);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
            this.Name = "Form1";
            this.Text = "Self Made Paint";
            this.vis_ColorGb.ResumeLayout(false);
            this.vis_ColorGb.PerformLayout();
            this.vis_FormGb.ResumeLayout(false);
            this.vis_FormGb.PerformLayout();
            this.vis_ToolboxGb.ResumeLayout(false);
            ((System.ComponentModel.ISupportInitialize)(this.ColorPb)).EndInit();
            ((System.ComponentModel.ISupportInitialize)(this.DrawBoxPb)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.PictureBox DrawBoxPb;
        private System.Windows.Forms.TextBox RedTb;
        private System.Windows.Forms.TextBox GreenTb;
        private System.Windows.Forms.TextBox BlueTb;
        private System.Windows.Forms.Label vis_LbRed;
        private System.Windows.Forms.Label vis_GreenLb;
        private System.Windows.Forms.Label vis_BlueLb;
        private System.Windows.Forms.GroupBox vis_ColorGb;
        private System.Windows.Forms.PictureBox ColorPb;
        private System.Windows.Forms.GroupBox vis_FormGb;
        private System.Windows.Forms.CheckBox FillCbox;
        private System.Windows.Forms.ComboBox FormsCb;
        private System.Windows.Forms.CheckBox LiveCbox;
        private System.Windows.Forms.Button ClearBtn;
        private System.Windows.Forms.GroupBox vis_ToolboxGb;
        private System.Windows.Forms.Panel FillPnl;
        private System.Windows.Forms.Panel CursorPnl;
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace SelfMadePaint
{
    public partial class Form1 : Form
    {
        private List<PBForm> DrawForms = new List<PBForm>();
        private Color SelectedColor;
        private PBForm SelectedForm;
        private Vector2 FirstPosition;
        private bool Live;
        private bool Dragging;
        private bool Fill;

        public Form1()
        {
            InitializeComponent();
            InitOwnComps();
        }

        private void InitOwnComps()
        {
            DrawBoxPb.Image = new Bitmap(DrawBoxPb.Width, DrawBoxPb.Height);

            RedTb.Text = "180";
            GreenTb.Text = "70";
            BlueTb.Text = "0";

            FormsCb.Items.Add(new PBLine());
            FormsCb.Items.Add(new PBRectangle());
            FormsCb.Items.Add(new PBCircle());
            FormsCb.SelectedIndex = 0;

            Live = LiveCbox.Checked;

            CursorPnl.BorderStyle = BorderStyle.Fixed3D;
            FillPnl.BorderStyle = BorderStyle.None;
        }

        private void SetImage(Bitmap bmp)
        {
            if (DrawBoxPb.Image != null && DrawBoxPb.Image != bmp)
                DrawBoxPb.Image.Dispose();
            DrawBoxPb.Image = bmp;
        }

        private void DrawBoxPb_Paint(object sender, PaintEventArgs e)
        {
            Bitmap bmp = new Bitmap(DrawBoxPb.Width, DrawBoxPb.Height);
            Graphics g = Graphics.FromImage(bmp);
            foreach (PBForm el in DrawForms)
            {
                if (el.FirstPosition != null && el.SecondPosition != null)
                    el.Draw(g);
            }
            SetImage(bmp);
        }

        private void TbOnlyNumbers(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
                (e.KeyChar != '.'))
            {
                e.Handled = true;
            }

            // only allow one decimal point
            if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
            {
                e.Handled = true;
            }
        }

        private void TbColorChanged(object sender, EventArgs e)
        {
            if ((sender as TextBox).Text.Length <= 0)
                (sender as TextBox).Text = "0";

            int r = Convert.ToInt32(RedTb.Text) > 255 ? 255 : Convert.ToInt32(RedTb.Text);
            int g = Convert.ToInt32(GreenTb.Text) > 255 ? 255 : Convert.ToInt32(GreenTb.Text);
            int b = Convert.ToInt32(BlueTb.Text) > 255 ? 255 : Convert.ToInt32(BlueTb.Text);

            SelectedColor = Color.FromArgb(r, g, b);
            ColorPb.BackColor = SelectedColor;
        }

        private void FormsCb_SelectedIndexChanged(object sender, EventArgs e)
        {
            SelectedForm = (FormsCb.SelectedItem as PBForm).NewInstance();
        }

        private void DrawBoxPb_MouseDown(object sender, MouseEventArgs e)
        {
            if (!Fill)
            {
                Dragging = true;
                FirstPosition = (Vector2)DrawBoxPb.PointToClient(Cursor.Position);
                SelectedForm.FirstPosition = FirstPosition;
                SelectedForm.Color = SelectedColor;
                SelectedForm.Fill = FillCbox.Checked;
                DrawForms.Add(SelectedForm);
            }
            else
            {
                FillSelectedArea((Vector2)DrawBoxPb.PointToClient(Cursor.Position));
            }
        }

        private void DrawBoxPb_MouseUp(object sender, MouseEventArgs e)
        {
            Dragging = false;

            SetFormSize();

            DrawBoxPb.Refresh();
            SelectedForm = (FormsCb.SelectedItem as PBForm).NewInstance();
        }

        private void LiveCbox_CheckedChanged(object sender, EventArgs e)
        {
            Live = LiveCbox.Checked;
        }

        private void DrawBoxPb_MouseMove(object sender, MouseEventArgs e)
        {
            if (Live && Dragging)
            {
                SetFormSize();

                DrawBoxPb.Refresh();
            }
        }

        private void SetFormSize()
        {
            Vector2 secondPosition = ((Vector2)DrawBoxPb.PointToClient(Cursor.Position));
            SelectedForm.SecondPosition = secondPosition;
        }

        private void ClearPaintArea()
        {
            DrawForms = new List<PBForm>();
            DrawBoxPb.Refresh();
        }

        private void ClearBtn_Click(object sender, EventArgs e)
        {
            ClearPaintArea();
        }

        private void FillSelectedArea(Vector2 position)
        {
            Bitmap bmp = (Bitmap)DrawBoxPb.Image;
            Color col = bmp.GetPixel((int)position.X, (int)position.Y);
            List<Vector2> pixels = new List<Vector2>();
            List<Vector2> closedPixels = new List<Vector2>();
            pixels.Add(position);

            while (pixels.Count > 0)
            {
                Vector2 vec = pixels[0];
                bmp.SetPixel((int)vec.X, (int)vec.Y, SelectedColor);
                DrawForms.Add(new PBRectangle(vec, vec + new Vector2(1, 1), SelectedColor, true));
                pixels.Remove(vec);

                Vector2 l = vec.GetLNeighbor();
                Vector2 r = vec.GetRNeighbor();
                Vector2 t = vec.GetTNeighbor();
                Vector2 b = vec.GetBNeighbor();

                if (vec.X > 0 && bmp.GetPixel((int)l.X, (int)l.Y).Equals(col) && !pixels.Contains(l))
                {
                    pixels.Add(l);
                }

                if (vec.Y > 0 && bmp.GetPixel((int)b.X, (int)b.Y).Equals(col) && !pixels.Contains(b))
                {
                    pixels.Add(b);
                }

                if (vec.X < bmp.Width-1 && bmp.GetPixel((int)r.X, (int)r.Y).Equals(col) && !pixels.Contains(r))
                {
                    pixels.Add(r);
                }

                if (vec.Y < bmp.Height-1 && bmp.GetPixel((int)t.X, (int)t.Y).Equals(col) && !pixels.Contains(t))
                {
                    pixels.Add(t);
                }
            }
            SetImage(bmp);
        }

        private void CursorPnl_Click(object sender, EventArgs e)
        {
            Fill = false;
            CursorPnl.BorderStyle = BorderStyle.Fixed3D;
            FillPnl.BorderStyle = BorderStyle.None;
        }

        private void FillPnl_Click(object sender, EventArgs e)
        {
            Fill = true;
            CursorPnl.BorderStyle = BorderStyle.None;
            FillPnl.BorderStyle = BorderStyle.Fixed3D;
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;

namespace SelfMadePaint
{
    public abstract class PBForm
    {
        public abstract Vector2 FirstPosition { get; set; }
        public abstract Vector2 SecondPosition { get; set; }
        public abstract Vector2 Size { get; set; }
        public abstract Boolean RevX { get; set; }
        public abstract Boolean RevY { get; set; }
        public abstract Boolean Fill { get; set; }
        public abstract Color Color { get; set; }
        public abstract void Draw(Graphics g);
        public abstract PBForm NewInstance(PBForm form);
        public abstract PBForm NewInstance();
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SelfMadePaint
{
    public class Vector2
    {
        public float X { get; set; }
        public float Y { get; set; }

        public Vector2(float x, float y)
        {
            X = x;
            Y = y;
        }

        public Vector2()
        {
            X = 0;
            Y = 0;
        }

        public Vector2 NewInstance()
        {
            return new Vector2(X, Y);
        }

        public static explicit operator Vector2(System.Drawing.Point p)
        {
            return new Vector2(p.X, p.Y);
        }

        public static explicit operator System.Drawing.Point(Vector2 vec)
        {
            return new System.Drawing.Point((int)vec.X, (int)vec.Y);
        }

        public static Vector2 operator +(Vector2 vec1, Vector2 vec2)
        {
            return new Vector2(vec1.X + vec2.X, vec1.Y + vec2.Y);
        }

        public static Vector2 operator -(Vector2 vec1, Vector2 vec2)
        {
            return new Vector2(vec1.X - vec2.X, vec1.Y - vec2.Y);
        }

        public static Vector2 operator *(Vector2 vec1, Vector2 vec2)
        {
            return new Vector2(vec1.X * vec2.X, vec1.Y * vec2.Y);
        }

        public static Vector2 operator /(Vector2 vec1, Vector2 vec2)
        {
            return new Vector2(vec1.X / vec2.X, vec1.Y / vec2.Y);
        }

        public override bool Equals(object obj)
        {
            return ((obj as Vector2).X == X && (obj as Vector2).Y == Y);
        }

        public Vector2 GetLNeighbor()
        {
            return new Vector2(X - 1, Y);
        }

        public Vector2 GetRNeighbor()
        {
            return new Vector2(X + 1, Y);
        }

        public Vector2 GetTNeighbor()
        {
            return new Vector2(X, Y + 1);
        }

        public Vector2 GetBNeighbor()
        {
            return new Vector2(X, Y - 1);
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;

namespace SelfMadePaint
{
    public class PBCircle : PBForm
    {
        public override Vector2 FirstPosition { get; set; }
        public override Vector2 SecondPosition { get; set; }
        public override Vector2 Size
        {
            get
            {
                return SecondPosition - FirstPosition;
            }
            set { }
        }
        public override Color Color { get; set; }
        public override bool Fill { get; set; }
        public override bool RevX { get; set; }
        public override bool RevY { get; set; }

        public PBCircle()
        {
        }

        public PBCircle(Vector2 firstPosition, Vector2 size, Color color, bool fill)
        {
            FirstPosition = firstPosition;
            Size = size;
            Color = color;
            Fill = fill;
        }

        public override void Draw(Graphics g)
        {
            if (Fill)
                g.FillEllipse(new SolidBrush(Color), FirstPosition.X, FirstPosition.Y, Size.X, Size.Y);
            else
                g.DrawEllipse(new Pen(Color), FirstPosition.X, FirstPosition.Y, Size.X, Size.Y);
        }

        public override string ToString()
        {
            return "Circle";
        }

        public override PBForm NewInstance(PBForm form)
        {
            return new PBCircle(form.FirstPosition, form.Size, form.Color, form.Fill);
        }
        public override PBForm NewInstance()
        {
            return new PBCircle();
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;

namespace SelfMadePaint
{
    public class PBLine : PBForm
    {
        public override Vector2 FirstPosition { get; set; }
        public override Vector2 SecondPosition { get; set; }
        public override Vector2 Size { get; set; }
        public override Color Color { get; set; }
        public override bool Fill { get; set; }
        public override bool RevX { get; set; }
        public override bool RevY { get; set; }

        public PBLine()
        {
        }

        public PBLine(Vector2 firstPosition, Vector2 size, Color color)
        {
            FirstPosition = firstPosition;
            Size = size;
            Color = color;
        }

        public override void Draw(Graphics g)
        {
            g.DrawLine(new Pen(Color), (Point)FirstPosition, (Point)SecondPosition);
        }

        public override string ToString()
        {
            return "Line";
        }

        public override PBForm NewInstance(PBForm form)
        {
            return new PBLine(form.FirstPosition, form.Size, form.Color);
        }

        public override PBForm NewInstance()
        {
            return new PBLine();
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;

namespace SelfMadePaint
{
    public class PBRectangle : PBForm
    {
        public override Vector2 FirstPosition { get; set; }
        public override Vector2 SecondPosition { get; set; }
        public override Vector2 Size { get; set; }
        public override Color Color { get; set; }
        public override bool Fill { get; set; }
        public override bool RevX { get; set; }
        public override bool RevY { get; set; }

        public PBRectangle()
        {
        }

        public PBRectangle(Vector2 firstPosition, Vector2 secondPosition, Color color, bool fill)
        {
            FirstPosition = firstPosition;
            SecondPosition = secondPosition;
            Color = color;
            Fill = fill;
        }

        public override void Draw(Graphics g)
        {
            Vector2 newSize = SecondPosition - FirstPosition;
            Vector2 newFirstposition = FirstPosition.NewInstance();

            if (SecondPosition.X < FirstPosition.X)
            {
                newFirstposition.X = SecondPosition.X;
                newSize.X = Math.Abs(newSize.X);
            }

            if (SecondPosition.Y < FirstPosition.Y)
            {
                newFirstposition.Y = SecondPosition.Y;
                newSize.Y = Math.Abs(newSize.Y);
            }

            if (Fill)
                g.FillRectangle(new SolidBrush(Color), newFirstposition.X, newFirstposition.Y, newSize.X, newSize.Y);
            else
                g.DrawRectangle(new Pen(Color), newFirstposition.X, newFirstposition.Y, newSize.X, newSize.Y);
        }

        public override string ToString()
        {
            return "Rectangle";
        }

        public override PBForm NewInstance(PBForm form)
        {
            return new PBRectangle(form.FirstPosition, form.Size, form.Color, form.Fill);
        }
        public override PBForm NewInstance()
        {
            return new PBRectangle();
        }
    }
}