c#图形开票画，没有释放资源。

Code
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;


namespace WindowsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            panel1.BackColor = Color.Transparent;
        }

        //文件名字,文件路径
        private string filename;
        private string filepath;
        //panel2底色,panel1,drawstring,drawimage,panel3画,线,圆,矩形

        private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            openFileDialog1.FileName = "*.sdg";
            openFileDialog1.Filter = "接线图(*.sdg)|*.sdg";
            openFileDialog1.RestoreDirectory = true;
            openFileDialog1.FilterIndex = 1;
            //openFileDialog1.ShowDialog();
            if (this.openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read);
                FileInfo info = new FileInfo(openFileDialog1.FileName);
                filepath = info.ToString();
                filename = filepath.Substring(filepath.Length - 3, 3);
                panel1.Refresh();
            }
        }

        private void panel1_Paint(object sender, PaintEventArgs e)
        {
            if (filename == "SDG")
            {
                FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read);
                FileInfo info = new FileInfo(openFileDialog1.FileName);
                filepath = info.ToString();
                BinaryReader reader = new BinaryReader(fs);
                byte[] by = new byte[info.Length];
                reader.Read(by, 0, by.Length);

                //文件以sdg开头
                if (by[0] == 83 && by[1] == 68 && by[2] == 71)
                {
                    //底色
                    panel2.BackColor = Color.FromArgb(by[61], by[60], by[59]);
                    for (int i = 0; i < by.Length; i++)
                    {
                        //画线
                        if (by[i] == 24 && by[i + 1] == 76 && by[i + 13] == 0)
                        {
                            //Graphics gs = panel3.CreateGraphics();
                            Graphics gs = e.Graphics;
                            // 取颜色
                            if (by[i + 15] == 255 && by[i + 16] == 255 && by[i + 17] == 255)
                            {
                                Point p = new Point(by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30] - 4, by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28] - 4);                               
                                Image image = global::WindowsApplication3.Properties.Resources.接地线;
                                gs.DrawImage(image ,p );                                
                                //lb.Click += new System.EventHandler(lb_Click);                               
                            }
                            else
                            {
                                Pen p = new Pen(Color.FromArgb(by[i + 17], by[i + 16], by[i + 15]));
                                //笔的宽度
                                p.Width = by[i + 20];
                                //画线，起点坐标，终点坐标，没有考虑线的粗细，缺少线的mode,style
                                gs.DrawLine(p, by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30], by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28], by[i + 9] * 256 + by[i + 10] + by[i - 31] * 256 + by[i - 30], by[i + 11] * 256 + by[i + 12] + by[i - 29] * 256 + by[i - 28]);
                                //MessageBox.Show(by[i+6].ToString ());
                            }
                        }
                        //画圆
                        if (by[i] == 23 && by[i + 1] == 67 && by[i + 2] == 105)
                        {
                            Graphics gs = e.Graphics;
                            Pen p = new Pen(Color.FromArgb(by[i + 16], by[i + 15], by[i + 14]));
                            p.Width = by[i + 19];
                            //圆
                            gs.DrawEllipse(p, by[i + 7] * 256 + by[i + 8] + by[i - 31] * 256 + by[i - 30] - (by[i + 11] * 256 + by[i + 12]), by[i + 9] * 256 + by[i + 10] + by[i - 29] * 256 + by[i - 28] - (by[i + 11] * 256 + by[i + 12]), (by[i + 11] * 256 + by[i + 12]) * 2, (by[i + 11] * 256 + by[i + 12]) * 2);
                            //MessageBox.Show(by[i + 8].ToString());
                        }
                         //画矩形
                        if (by[i] == 24 && by[i + 1] == 76 && by[i + 13] == 1)
                        {
                            //添加柜门
                            if (by[i + 15] == 128 && by[i + 16] == 128 && by[i + 17] == 128)
                            {
                                Graphics gs = e.Graphics;
                                Point p = new Point(by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30], by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28]);
                                Image image = global::WindowsApplication3.Properties.Resources.柜门 ;
                                gs.DrawImage(image, p); 
                                
                                //lb.Click += new System.EventHandler(lb_Click);
                            }
                            //添加断路器
                            if (by[i + 15] == 0 && by[i + 16] == 255 && by[i + 17] == 255)
                            {
                                Graphics gs = e.Graphics;
                                Point p = new Point(by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30], by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28]);
                                Image image = global::WindowsApplication3.Properties.Resources.断路器 ;
                                gs.DrawImage(image, p);                               
                                //lb.Click += new System.EventHandler(lb_Click);
                            }
                            //添加刀闸
                            if (by[i + 15] == 255 && by[i + 16] == 255 && by[i + 17] == 255)
                            {
                                //添加竖刀闸
                                if ((by[i + 9] * 256 + by[i + 10] + by[i - 31] * 256 + by[i - 30] - (by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30])) == 30)
                                {
                                    Graphics gs = e.Graphics;
                                    Point p = new Point(by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30], by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28] + 10);
                                    Image image = global::WindowsApplication3.Properties.Resources.横刀闸 ;
                                    gs.DrawImage(image, p);                                     
                                    //lb.Click += new System.EventHandler(lb_Click);
                                }
                                //添加横刀闸
                                if ((by[i + 9] * 256 + by[i + 10] + by[i - 31] * 256 + by[i - 30] - (by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30])) == 25)
                                {
                                    Graphics gs = e.Graphics;
                                    Point p = new Point(by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30] + 10, by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28]);
                                    Image image = global::WindowsApplication3.Properties.Resources.竖刀闸;
                                    gs.DrawImage(image, p);  
                                    //lb.Click += new System.EventHandler(lb_Click);
                                }

                                //else
                                //{
                                //    Graphics gs = panel1.CreateGraphics();
                                //    // 取颜色
                                //    Pen p = new Pen(Color.FromArgb(by[i + 17], by[i + 16], by[i + 15]));
                                //    //笔的宽度 
                                //    p.Width = by[i + 20];
                                //    //画线，起点坐标，终点坐标，没有考虑线的粗细，缺少线的mode,style
                                //    gs.DrawRectangle(p, by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30], by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28], by[i + 9] * 256 + by[i + 10] + by[i - 31] * 256 + by[i - 30] - (by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30]), by[i + 11] * 256 + by[i + 12] + by[i - 29] * 256 + by[i - 28] - (by[i + 7] * 256 + by[i + 8] + by[i - 29] * 256 + by[i - 28]));
                                //    //    MessageBox.Show(by[i-47].ToString());  
                                //}
                                //单击label控件
                                //lb.Click += new System.EventHandler(lb_Click);                           
                            }                           
                        }
                        //文本,具体位置已经取出，用的gb2312编码方式.
                        if (by[i] == 84 && by[i + 1] == 101 && by[i + 2] == 120 && by[i + 3] == 116)
                        {
                            byte[] bt = new byte[50];
                            string text;
                            int size;
                            size = by[i + 10] * 256 + by[i + 11];
                            Font drawFont = new Font("宋体", size);
                            SolidBrush drawBrush = new SolidBrush(Color.FromArgb(by[i + 15], by[i + 14], by[i + 13]));
                            PointF drawPoint = new PointF(by[i + 4] * 256 + by[i + 5] + by[i - 32] * 256 + by[i - 31], by[i + 6] * 256 + by[i + 7] + by[i - 30] * 256 + by[i - 29]);                         
                            for (int j = 0; j < by[i + 18]; j++, i++)
                            {
                                bt[j] = by[i + 19];
                            }
                            text = Encoding.GetEncoding("gb2312").GetString(bt);                           
                            e.Graphics.DrawString(text,drawFont ,drawBrush ,drawPoint );                                                                          
                        }
                    }
                }
                fs.Close();
            }
        }

        private void 退出ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                if(e.X >16&&e.X <30&&e.Y>17&&e.Y <40)

                //if (e.X > (by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30]) && e.X < (by[i + 5] * 256 + by[i + 6] + by[i - 31] * 256 + by[i - 30]) + 12)
                //    MessageBox.Show("ddd");
                    MessageBox.Show(e.X.ToString());
                //if()
            }
        }       
    }
}