.NET標準Frameworkで圧縮/解凍が可能なクラスについて

        private void Compress(string inFile,string outFile)
        {
            FileStream fs=new FileStream(inFile ,FileMode.Open,FileAccess.Read,FileShare.ReadWrite);
            BinaryReader br=new BinaryReader(fs);
            int length=(int)(fs.Length+4);
            int pixels=(int)(length+2)/3;
            int Width=((int)((System.Math.Sqrt(pixels))+8)/8)*8;
            Bitmap target=new Bitmap(Width,Width,PixelFormat.Format24bppRgb);
            byte[] content=br.ReadBytes((int)fs.Length);
            br.Close();
            byte[] buf = new byte[length];
            buf[0]=(byte)((length>>0)&0xff);
            buf[1]=(byte)((length>>8)&0xff);
            buf[2]=(byte)((length>>16)&0xff);
            buf[3]=(byte)((length>>24)&0xff);
            for(int ptr=4;ptr<length;ptr++) buf[ptr]=content[ptr-4];
            BitmapData dat = target.LockBits(new Rectangle(0,0,Width,Width),ImageLockMode.ReadWrite,PixelFormat.Format24bppRgb);
            Marshal.Copy(buf,0,dat.Scan0,length);
            target.UnlockBits(dat);
            target.Save(outFile,ImageFormat.Png);

        }
        private void DeCompress(string inFile,string outFile)
        {
            Image target=Image.FromFile(inFile);
            BitmapData dat = ((Bitmap)target).LockBits(new Rectangle(0,0,target.Width,target.Height),ImageLockMode.ReadWrite,PixelFormat.Format24bppRgb);
            int [] lgs=new int[1];
            Marshal.Copy(dat.Scan0,lgs,0,1);
            byte[] buf=new byte[lgs[0]];
            Marshal.Copy(dat.Scan0,buf,0,lgs[0]);
            FileStream fs=new FileStream(outFile ,FileMode.OpenOrCreate,FileAccess.Write,FileShare.ReadWrite);
            BinaryWriter bw=new BinaryWriter(fs);
            bw.Write(buf,4,lgs[0]-4);
            bw.Close();
        }