AlphaBlend with CF2

using System;
 
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
 
namespace ctrlDevice
{
    public partial class tButton : Control
    {
        public event EventHandler onClick;
 
        Bitmap _image;
        Bitmap _hover;
 
        protected virtual void DoClick(EventArgs e)
        {
            EventHandler _onClick = this.onClick;
            if (_onClick != null)
            {
                onClick(this, e);
            }
        }
 
        public Bitmap Image
        {
            get { return _image; }
            set
            {
                _image = value;
            }
        }
 
        public Bitmap HoverImage
        {
            get { return _hover; }
            set { _hover = value; }
        }
 
        public tButton()
        {
            InitializeComponent();
        }
 
        protected override void OnPaint(PaintEventArgs pe)
        {
            Graphics g = pe.Graphics;
            DrawAlpha(gx, _image, 0, this.Location.X, this.Location.Y);
            // Calling the base class OnPaint
            // base.OnPaint(pe);
        }
 
        private void DrawAlpha(Graphics gx, Bitmap image, byte transp, int x, int y)
        {
            using (Graphics gxSrc = Graphics.FromImage(image))
            {
                IntPtr hdcDst = gx.GetHdc();
                IntPtr hdcSrc = gxSrc.GetHdc();
                BlendFunction blendFunction = new BlendFunction();
                blendFunction.BlendOp = (byte)BlendOperation.AC_SRC_OVER;   // Only supported blend operation
                blendFunction.BlendFlags = (byte)BlendFlags.Zero;           // Documentation says put 0 here
                blendFunction.SourceConstantAlpha = transp;// Constant alpha factor
                blendFunction.AlphaFormat = (byte)0;                        // Don't look for per pixel alpha
                PlatformAPIs.AlphaBlend(hdcDst, x, y, image.Width, image.Height, hdcSrc, 0, 0, image.Width, image.Height, blendFunction);
                gx.ReleaseHdc(hdcDst);    // Required cleanup to GetHdc()
                gxSrc.ReleaseHdc(hdcSrc);       // Required cleanup to GetHdc()
            }
        }
    }
}