A Simple Panning PictureBox

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;

namespace DDPanBox
{
    class DDPanBox : Control
    {
        public DDPanBox()
        {
            //Set up double buffering and a little extra.
            this.SetStyle(ControlStyles.UserPaint | ControlStyles.OptimizedDoubleBuffer |
            ControlStyles.AllPaintingInWmPaint | ControlStyles.SupportsTransparentBackColor,
            true);

          //set the part of the source image to be drawn.
          //DrawRect = DeflateRect(ClientRectangle, Padding);
            DrawRect = ClientRectangle;

          //Subscribe to our event handlers.
          this.MouseDown += new MouseEventHandler(panBox_MouseDown);
          this.MouseMove += new MouseEventHandler(panBox_MouseMove);
          this.MouseUp += new MouseEventHandler(panBox_MouseUp);
          this.Resize += new EventHandler(panBox_Resize);

        }
        //if true were at 2:1 false then 1:1
        bool zoom = false;

        bool dragging = false; //Tells us if our image has been clicked on.

        Point start = new Point(); //Keep initial click for accurate panning.

        void panBox_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                dragging = true;
                //offset new point by original one so we know where in the image we are.
                start = new Point(e.Location.X + DrawRect.Location.X, e.Location.Y + DrawRect.Location.Y);
                Cursor = Cursors.SizeAll; //just for looks.
            }
            else if (e.Button == MouseButtons.Right)
            {
                zoom = !zoom;
                if (zoom)
                {
                    // modify the drawrect to a smaller rectangle to zoom, and center it in previous drawrect
                    DrawRect = new Rectangle(DrawRect.X + ClientRectangle.Width / 4, DrawRect.Y + ClientRectangle.Height / 4, DrawRect.Width / 2, DrawRect.Height / 2);
                }
                else
                {
                    //Do the reverse of above
                    DrawRect = new Rectangle(DrawRect.X - ClientRectangle.Width/4, DrawRect.Y - ClientRectangle.Height/4, ClientRectangle.Width, ClientRectangle.Height);
                }
                //Calculate Draw Rectangle by calling the resize event.
                panBox_Resize(null, EventArgs.Empty);
            }
        }

        void panBox_MouseMove(object sender, MouseEventArgs e)
        {
            if (dragging)
            {
                DrawRect.Location = new Point(start.X - e.Location.X, start.Y - e.Location.Y);

                if (DrawRect.Location.X < 0 -Padding.Left)
                    DrawRect.Location = new Point(0 - Padding.Left, DrawRect.Location.Y);

                if (DrawRect.Location.Y < 0 - Padding.Top)
                    DrawRect.Location = new Point(DrawRect.Location.X, 0 - Padding.Top);

                if (DrawRect.Location.X > _Image.Width - DrawRect.Width + Padding.Right)
                    DrawRect.Location = new Point(_Image.Width - DrawRect.Width + Padding.Right, DrawRect.Location.Y);

                if (DrawRect.Location.Y > _Image.Height - DrawRect.Height + Padding.Bottom)
                    DrawRect.Location = new Point(DrawRect.Location.X, _Image.Height - DrawRect.Height + Padding.Bottom);

                this.Refresh();
            }
        }

        void panBox_MouseUp(object sender, MouseEventArgs e)
        {
            dragging = false;
            Cursor = Cursors.Default;
        }

        void panBox_Resize(object sender, EventArgs e)
        {
            if (_Image != null)
            {
                if (zoom)
                {
                    DrawRect = new Rectangle(DrawRect.Location.X, DrawRect.Location.Y, ClientRectangle.Width / 2, ClientRectangle.Height / 2);
                }
                else
                    DrawRect = new Rectangle(DrawRect.Location.X, DrawRect.Location.Y, ClientRectangle.Width, ClientRectangle.Height);

                if (DrawRect.Location.X < 0 - Padding.Left)
                    DrawRect.Location = new Point(0 - Padding.Left, DrawRect.Location.Y);

                if (DrawRect.Location.Y < 0 - Padding.Top)
                    DrawRect.Location = new Point(DrawRect.Location.X, 0 - Padding.Top);

                if (DrawRect.Location.X > _Image.Width - DrawRect.Width + Padding.Right)
                    DrawRect.Location = new Point(_Image.Width - DrawRect.Width + Padding.Right, DrawRect.Location.Y);

                if (DrawRect.Location.Y > _Image.Height - DrawRect.Height + Padding.Bottom)
                    DrawRect.Location = new Point(DrawRect.Location.X, _Image.Height - DrawRect.Height + Padding.Bottom);

                this.Refresh();
            }
        }

        private Image _Image;

        public Image Image
        {
            get
            {
                return _Image;
            }
            set
            {
                _Image = value;
                //Calculate Draw Rectangle by calling the resize event.
                panBox_Resize(this, EventArgs.Empty);
            }
        }

        private Rectangle DrawRect;


        protected override void OnPaint(PaintEventArgs e)
        {
            if (_Image != null)
            {
                e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                e.Graphics.DrawImage(_Image, ClientRectangle, DrawRect, GraphicsUnit.Pixel);

                if(zoom)
                    e.Graphics.DrawString("Zoom 2:1", this.Font, Brushes.White, new PointF(15F, 15F));
                else
                    e.Graphics.DrawString("Zoom 1:1", this.Font, Brushes.White, new PointF(15F, 15F));
            }

            base.OnPaint(e);
        }

        public static Rectangle DeflateRect(Rectangle rect, Padding padding)
        {
            rect.X += padding.Left;
            rect.Y += padding.Top;
            rect.Width -= padding.Horizontal;
            rect.Height -= padding.Vertical;
            return rect;

        }

        

        
    }
}