使用双缓冲来减少闪烁现象

相关连接
http://www.microsoft.co.ke/china/msdn/archives/library/dnnetcomp/html/imagebutton.asp

protected   override   void  OnPaint(PaintEventArgs e )
{
    Graphics gxOff; //屏幕外的图像

    if (m_bmpOffscreen == null) //要双缓冲的位图
    {
        m_bmpOffscreen = new Bitmap(ClientSize.Width, ClientSize.Height);
    }
 
    gxOff = Graphics.FromImage(m_bmpOffscreen);

    gxOff.Clear(this.BackColor);
    //绘制一些位图
    gxOff.DrawImage(bmpParent, 0, 0, bmpRect, GraphicsUnit.Pixel);

    //边界矩形
    Rectangle rc = this.ClientRectangle;
    rc.Width--;
    rc.Height--;
    
    //绘制边界
    gxOff.DrawRectangle(new Pen(Color.Black), rc);
    //从内存位图绘制
    e.Graphics.DrawImage(m_bmpOffscreen, 0, 0);

    base.OnPaint(e);
}

绘制位图时需要聪明些

         protected   override   void  OnPaint(System.Windows.Forms.PaintEventArgs e)
         {
            Bitmap m_bmpOffscreen = null;

            Graphics gxOff; //Offscreen graphics
            Rectangle imgRect; //image rectangle
            Brush backBrush; //brush for filling a backcolor

            if (m_bmpOffscreen == null) //Bitmap for doublebuffering
            {
                m_bmpOffscreen = new Bitmap(ClientSize.Width, ClientSize.Height);
            }

            gxOff = Graphics.FromImage(m_bmpOffscreen);
            gxOff.Clear(this.BackColor);

            if (!bPushed) 
                backBrush = new SolidBrush(this.BackColor);
            else //change the background when it's pressed
                backBrush = new SolidBrush(Color.LightGray);
            gxOff.FillRectangle(backBrush, this.ClientRectangle);

            if (this.mImage != null)
            {
                //Center the image relativelly to the control
                int imageLeft = (this.Width - mImage.Width) / 2;
                int imageTop = (this.Height - mImage.Height) / 2;

                if (!bPushed)
                {
                    imgRect = new Rectangle(imageLeft, imageTop, mImage.Width,mImage.Height);
                }
                else //The button was pressed
                {
                    //Shift the image by one pixel
                    imgRect = new Rectangle(imageLeft + 1, imageTop + 1, mImage.Width, 
                        mImage.Height);
                }
                //设置色键（透明范围）
                ImageAttributes imageAttr = new ImageAttributes();
                imageAttr.SetColorKey(BackgroundImageColor(mImage),
                    BackgroundImageColor(mImage));//以图片的背景作为透明范围
                //Draw image
                gxOff.DrawImage(mImage, imgRect, 0, 0, mImage.Width, mImage.Height,
                    GraphicsUnit.Pixel, imageAttr); 

            }

            if (bPushed) //The button was pressed
            {
                //Prepare rectangle
                Rectangle rc = this.ClientRectangle;
                rc.Width--;
                rc.Height--;
                //Draw rectangle
                gxOff.DrawRectangle(new Pen(Color.Black), rc);
            }

            gxOff.DrawRectangle(Pens.Black,0,0,this.Width-1,this.Height-1);
            switch(this._drawKind)
            {
                case DrawKinds.Selected:
                    gxOff.DrawRectangle(Pens.Red,1,1,this.Width-3,this.Height-3);
                    break;
            }

            //Draw from the memory bitmap
            e.Graphics.DrawImage(m_bmpOffscreen, 0, 0);

            base.OnPaint(e);
        }

         /**/ /// <summary>
        /// 获取图片的背景色
        /// </summary>
        /// <param name="image"></param>
        /// <returns></returns>
         private  Color BackgroundImageColor(Image image)
         {
            Bitmap bmp = new Bitmap(image);
            return bmp.GetPixel(0, 0);//取第一个点的颜色作为其背景色
        }