图片显示的质量问题

我继承了button 用Image.fromfile 加载图片 再 加到imageList 中  然后再 用Graphics 画上
就会发现图片显示的质量有问题using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace TestButton
{
    public partial class UserControl1 : System.Windows.Forms.Panel
    {
        private string none ;       //什么都没有的情况
        private string hover;      // 鼠标 划过 悬停的时候路径
        private string click ;      //鼠标电击时候的图片路径
        private Image image;
        private int ww;
        private int hh;
        private bool ok;
        private bool error;
        private LinearGradientBrush linGrBrush;
        private bool showfont;       
        public UserControl1()
        {
            this.MouseDown += new MouseEventHandler(UserControl1_MouseDown);
            this.MouseHover += new EventHandler(UserControl1_MouseHover);
            this.MouseLeave += new EventHandler(UserControl1_MouseLeave);
            this.MouseUp += new MouseEventHandler(UserControl1_MouseUp);
            this.MouseEnter += new EventHandler(UserControl1_MouseEnter);
            InitializeComponent();
        }        private void tests()
        {
            string nones = Application.StartupPath + "\\" + this.none;
            string clicks = Application.StartupPath + "\\" + this.click;
            string hovers = Application.StartupPath + "\\" + this.hover;
            try 
            {   
                
                    Image im1 = Image.FromFile(nones,false);
                    Image im2 = Image.FromFile(hovers, false);
                    Image im3 = Image.FromFile(clicks, false);
                    this.ww = im1.Width;
                    this.hh = im1.Height;
                    Size s = new Size();
                    s.Width = this.ww;
                    s.Height = this.hh;
                    this.imageList1.ImageSize = s;
                    this.imageList1.Images.AddRange(new Image[] { im1, im2, im3 });            }catch(Exception e){
                    this.error = true;
            }
       }        protected override void  OnPaint(PaintEventArgs pevent)
        {
           
           base.OnPaint(pevent);
            
            if (!this.ok)
            {
                this.tests();
                linGrBrush = new LinearGradientBrush(new Point(0, 0), new Point(0, 100), Color.White, Color.White);
                this.ok = true;
            }
            
            if(this.image == null)
                this.image = this.imageList1.Images[0];            if (this.error)
                 base.OnPaint(pevent);
            else 
            {
                this.ForeColor = Color.White;
                Graphics e = pevent.Graphics;
                
                int startx = pevent.ClipRectangle.X;
                int starty = pevent.ClipRectangle.Y;                this.Width = this.ww;
                this.Height = this.hh;
               
                SizeF f = e.MeasureString(Text, Font);
                float w = f.Width;
                float h = f.Height;
                w = (Size.Width - w) / 2;
                h = (Size.Height - h) / 2;
                this.BackgroundImage = this.image;
                //EncoderParameter ep = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality,100L);
                //ImageCodecInfo info = new ImageCodecInfo();
                //info.CodecName;
               // this.image.GetEncoderParameterList(System.Drawing.Imaging.Encoder.Quality);
         
            //    e.DrawImage(this.image, new Point(startx, starty));
                if(this.showfont)
                e.DrawString(Text, Font, linGrBrush, w, h);
            }
        }        public bool Showfont
        {
            get { return showfont; }
            set { showfont = value; }
        }        public string None
        {
            get { return none; }
            set { none = value; }
        }        public string Hover
        {
            get { return hover; }
            set { hover = value; }
        }        public string Click1
        {
            get { return click; }
            set { click = value; }
        }        void UserControl1_MouseEnter(object sender, EventArgs e)
        {
            if (!this.error)
            {
                this.image = this.imageList1.Images[1];
                this.Invalidate();
            }
        }        void UserControl1_MouseUp(object sender, MouseEventArgs e)
        {
            if (!this.error)
            {
                this.image = this.imageList1.Images[1];
                linGrBrush = new LinearGradientBrush(new Point(0, 0), new Point(0, 100), Color.White, Color.White);
                this.Invalidate();
            }
        }        void UserControl1_MouseLeave(object sender, EventArgs e)
        {
            if (!this.error)
            {
                this.image = this.imageList1.Images[0];
                this.Invalidate();
            }
        }        void UserControl1_MouseHover(object sender, EventArgs e)
        {
            if (!this.error)
            {
                this.image = this.imageList1.Images[1];
                this.Invalidate();
            }
        }        void UserControl1_MouseDown(object sender, MouseEventArgs e)
        {
            if (!this.error)
            {
                this.image = this.imageList1.Images[2];
                this.linGrBrush = new LinearGradientBrush(new Point(0, 0), new Point(0, 100), Color.Black, Color.Black);
                this.Invalidate();
            }
        }    }
}