Per Pixel Alpha Blend in C#

//
// Copyright � 2002-2004 Rui Godinho Lopes <rui@ruilopes.com>
// All rights reserved.
//
// This source file(s) may be redistributed unmodified by any means
// PROVIDING they are not sold for profit without the authors expressed
// written consent, and providing that this notice and the authors name
// and all copyright notices remain intact.
//
// Any use of the software in source or binary forms, with or without
// modification, must include, in the user documentation ("About" box and
// printed documentation) and internal comments to the code, notices to
// the end user as follows:
//
// "Portions Copyright � 2002-2004 Rui Godinho Lopes"
//
// An email letting me know that you are using it would be nice as well.
// That's not much to ask considering the amount of work that went into
// this.
//
// THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
// EXPRESS OR IMPLIED. USE IT AT YOUT OWN RISK. THE AUTHOR ACCEPTS NO
// LIABILITY FOR ANY DATA DAMAGE/LOSS THAT THIS PRODUCT MAY CAUSE.
//

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



/// <para>Our test form for this sample application.  The bitmap will be displayed in this window.</para>
class MyPerPixelAlphaForm : PerPixelAlphaForm
{
	public MyPerPixelAlphaForm()
	{
		TopMost = true;
		ShowInTaskbar = false;
	}


	// Let Windows drag this form for us
	protected override void WndProc(ref Message m)
	{
		if (m.Msg == 0x0084 /*WM_NCHITTEST*/) {
			m.Result= (IntPtr)2;	// HTCLIENT
			return;
		}
		base.WndProc(ref m);
	}
}



///<para>The "controller" dialog box.</para>
class MyForm : Form
{
	public MyForm()
	{
		Font= new Font("tahoma", 8);
		Text= "perpixelalpha# - Sample application";
		FormBorderStyle = FormBorderStyle.FixedDialog;
		MinimizeBox = false;
		MaximizeBox = false;
		ClientSize = new Size(350, 160);
		StartPosition = FormStartPosition.CenterScreen;

		AllowDrop = true; // Because we want to be a drop target of windows explorer files.

		InitializeComponent();
	}


	///<para>Constructs and initializes all child controls of this dialog box.</para>
	private void InitializeComponent()
	{
		// Label with to display current opacity level
		Label Label1 = new Label();
		Label1.AutoSize = true;
		Label1.Location = new System.Drawing.Point(4, 8);
		Label1.Text = "1. Drag&&Drop an image file from windows explorer into this window.";
		Controls.Add(Label1);

		Label Label2 = new Label();
		Label2.AutoSize = true;
		Label2.Location = new System.Drawing.Point(4, 38);
		Label2.Text = "2. Play with the opacity level [0..255]:";
		Controls.Add(Label2);

		// Label with to display current opacity level
		LabelValue = new Label();
		LabelValue.AutoSize = true;
		LabelValue.Location = new System.Drawing.Point(195, 38);
		LabelValue.Text = "255";

		Controls.Add(LabelValue);


		// Trackbar to change opacity level
		Track = new TrackBar();

		Track.Location = new System.Drawing.Point(18, 58);
		Track.Size = new System.Drawing.Size(310, 0);
		Track.BeginInit();
			Track.Maximum = 255;
			Track.TickFrequency = 5;
			Track.TickStyle = TickStyle.TopLeft;
			Track.Value = 255;
		Track.EndInit();

		Track.ValueChanged += new EventHandler(Track_ValueChanged);

		Controls.Add(Track);

		
		Label Label3 = new Label();
		Label3.AutoSize = true;
		Label3.Location = new System.Drawing.Point(4, 108);
		Label3.Text = "3. Drag the layered window arround you desktop!";
		Controls.Add(Label3);


		// Label with two links to me! :)
		LinkLabel Link = new LinkLabel();

		Link.Location = new System.Drawing.Point(4, 140);
		Link.Size = new System.Drawing.Size(250, 80);
		Link.Text = "by Rui Lopes <rui@ruilopes.com>";
		Link.Links.Add(3, 9,  "http://www.ruilopes.com");
		Link.Links.Add(14, 16, "mailto:rui@ruilopes.com");

		Link.LinkClicked += new LinkLabelLinkClickedEventHandler(Link_LinkClicked);

		Controls.Add(Link);


		// TestForm will containt the per-pixel-alpha dib
		TestForm = new MyPerPixelAlphaForm();
		TestForm.Show();
	}


	///<para>Frees our bitmap.</para>
	protected override void Dispose(bool disposing)
	{
		try {
			if (disposing && bitmap != null) {
				bitmap.Dispose();
				bitmap = null;
			}
		}
		finally {
			base.Dispose(disposing);
		}
	}


	///<para>Accepts only Drops of windows explorer files.</para>
	protected override void OnDragEnter(DragEventArgs e)
	{
		if (e.Data.GetDataPresent(DataFormats.FileDrop))
			e.Effect = DragDropEffects.Copy;
		base.OnDragEnter(e);
	}


	///<para>Just loads the dropped file from windows explorer.</para>
	protected override void OnDragDrop(DragEventArgs e)
	{
		string[] files= e.Data.GetData(DataFormats.FileDrop) as string[];
		if (files != null) {
			if (files.Length == 1)
				SetPerPixelBitmapFilename(files[0]);
			else
				MessageBox.Show(this, "Please, drop only one image file.", "Too many files dropped", MessageBoxButtons.OK, MessageBoxIcon.Stop);
		}
		base.OnDragDrop(e);
	}


	///<para>Just load a image file and display it on our test form.</para>
	private void SetPerPixelBitmapFilename(string fileName)
	{
		Bitmap newBitmap;

		try {

			newBitmap = Image.FromFile(fileName) as Bitmap;
			TestForm.SetBitmap(newBitmap, (byte)Track.Value);

		}
		catch (ApplicationException e) {
			MessageBox.Show(this, e.Message, "Error with bitmap.", MessageBoxButtons.OK, MessageBoxIcon.Error);
			return;
		}
		catch (Exception e) {
			MessageBox.Show(this, e.Message, "Could not open image file.", MessageBoxButtons.OK, MessageBoxIcon.Error);
			return;
		}

		if (bitmap != null)
			bitmap.Dispose();
		bitmap = newBitmap;
	}


	///<para>Change the opacity level of our test form.</para>
	private void Track_ValueChanged(object sender, EventArgs e)
	{
		byte opacity = (byte)Track.Value;
		LabelValue.Text = opacity.ToString();
		LabelValue.Refresh(); // We need this because on slow computers (mine!) the windows takes some time to update our label.

		if (bitmap != null)
			TestForm.SetBitmap(bitmap, opacity);		
	}


	///<para>Start the computer browser in the specified uri.</para>
	private void Link_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
	{
		e.Link.Visited = true;
		using (System.Diagnostics.Process.Start(e.Link.LinkData.ToString())) {
		}
	}


	private Label LabelValue;	// label with current opacity level
	private TrackBar Track;		// trackbar to chabge opacity level
	private MyPerPixelAlphaForm TestForm;	// our test form
	private Bitmap bitmap;		// bitmap that is currently displaying on our test form
}



// Our Great Application!
class TheApp
{
	[STAThread]
	public static void Main()
	{
		Application.Run(new MyForm());
	}
}