Adobe Color Picker Clone

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace DrawingEx.ColorManagement.ColorModels.Selection
{
	/// <summary>
	/// Zusammenfassung f�r ColorSelectionFader.
	/// </summary>
	[System.ComponentModel.ToolboxItem(false)]
	public class ColorSelectionFader:Control
	{
		#region variables
		private Bitmap _bmp=new Bitmap(1,1);
		private double _position=1.0;
		#endregion
		public ColorSelectionFader()
		{
			this.SetStyle(ControlStyles.AllPaintingInWmPaint |
				ControlStyles.DoubleBuffer |
				ControlStyles.UserPaint |
				ControlStyles.ResizeRedraw, true);
		}
		private Rectangle GetScrollerRectangle(double pos)
		{
			return new Rectangle(
				0,(int)(_position*(double)(this.Height-11)),
				this.Width-1,10);
		}
		#region controller
		protected override void OnSizeChanged(EventArgs e)
		{
			base.OnSizeChanged (e);
			if(_bmp!=null)
				_bmp.Dispose();
			_bmp=new Bitmap(Math.Max(1,this.Height-10),1,
				System.Drawing.Imaging.PixelFormat.Format32bppArgb);
		}

		protected override void OnPaint(PaintEventArgs e)
		{
			base.OnPaint (e);
			if(_bmp==null || this.Width<11 || this.Height<11) return;

			GraphicsState state=e.Graphics.Save();
			e.Graphics.InterpolationMode=InterpolationMode.NearestNeighbor;
			e.Graphics.PixelOffsetMode=PixelOffsetMode.HighQuality;

			e.Graphics.Transform=new Matrix(0f,1f,1f,0f,0f,0f);
			e.Graphics.DrawImage(_bmp,5,5,this.Height-11,this.Width-10);

			e.Graphics.Restore(state);
			//draw gridlines
			if((Control.ModifierKeys&Keys.Shift)!=0)
			{
				float dy=(float)(this.Height-11)/8f, y=5f;
				using(Pen pn=new Pen(new HatchBrush(HatchStyle.SmallCheckerBoard,
						  Color.FromArgb(80,255,255,255),
						  Color.FromArgb(0,0,0,0))))
				{
					for(int i=0;i<=8;i++,y+=dy)
					{
						e.Graphics.DrawLine(pn,5,(int)y,this.Width-6,(int)y);
					}
				}
			}
			e.Graphics.DrawRectangle(Pens.Silver,5,5,this.Width-11,this.Height-11);
			//draw fader
			Rectangle fader=GetScrollerRectangle(_position);
			e.Graphics.SmoothingMode=SmoothingMode.AntiAlias;
			Point[] points=
				new Point[]
						{
							new Point(fader.X+1,fader.Y), new Point(fader.X+4,fader.Y),
							new Point(fader.X+9,fader.Y+5),new Point(fader.X+4,fader.Bottom),
							new Point(fader.X+1,fader.Bottom),new Point(fader.X,fader.Bottom-1),
							new Point(fader.X,fader.Y+1)
						};
			e.Graphics.FillPolygon(Brushes.White,points);
			e.Graphics.DrawPolygon(Pens.Silver,points);
			points=
				new Point[]
						{
							new Point(fader.Right-1,fader.Y), new Point(fader.Right-4,fader.Y),
							new Point(fader.Right-9,fader.Y+5),new Point(fader.Right-4,fader.Bottom),
							new Point(fader.Right-1,fader.Bottom),new Point(fader.Right,fader.Bottom-1),
							new Point(fader.Right,fader.Y+1)
						};

			e.Graphics.FillPolygon(Brushes.White,points);
			e.Graphics.DrawPolygon(Pens.Silver,points);
		}
		protected override void OnMouseDown(MouseEventArgs e)
		{
			base.OnMouseDown (e);
			if(SetPosition(
				(double)(e.Y-5)/(double)Math.Max(1,this.Height-11)))
				RaiseScroll();
		}
		protected override void OnMouseMove(MouseEventArgs e)
		{
			base.OnMouseMove (e);
			if(e.Button==MouseButtons.Left)
				if(SetPosition(
					(double)(e.Y-5)/(double)Math.Max(1,this.Height-11)))
					RaiseScroll();
		}

		#endregion
		#region members
		public bool SetPosition(double value)
		{
			value=XYZ.ClipValue(value,0.0,1.0);
			if((Control.ModifierKeys&Keys.Shift)!=0)
			{
				value=Math.Round(value*8.0,0)/8.0;
			}
			if(value==_position) return false;
			this.Invalidate(Rectangle.Inflate(GetScrollerRectangle(_position),1,1));
			_position=value;
			this.Invalidate(Rectangle.Inflate(GetScrollerRectangle(_position),1,1));
			this.Update();
			return true;
		}
		#endregion
		internal Bitmap Image
		{
			get{return _bmp;}
		}
		internal double Position
		{
			get{return _position;}
			set{SetPosition(value);}
		}
		#region events
		private void RaiseScroll()
		{
			if(Scroll!=null)
				Scroll(this,EventArgs.Empty);
		}
		public event EventHandler Scroll;
		#endregion
	}
}