图片的缩略图

 private void text_Load(object sender, EventArgs e)
        {
       
        }
  /// <summary>
        /// 生成缩略图
         /// </summary>
        /// <param name="strOraginalPath"></param>
        ///
        public void GetThumb(string strOraginalPath)
        {
        int _iThumbMaxWidth = 400;//缩略图的最大宽度
        int _iThumbMaxHeight = 300;//缩略图的最大高度
     
            System.Drawing.Image imgOraginal = System.Drawing.Image.FromFile(strOraginalPath);
            int iOraginalWidth = imgOraginal.Width;
            int iOraginalHeight = imgOraginal.Height;

            int toWidth;
            int toHeight;

            //原图的宽高比
            float fWbH = (float)iOraginalWidth / (float)iOraginalHeight;
            //原图的高宽比
            float fHbW = (float)iOraginalHeight / (float)iOraginalWidth;

            //如果宽高比大于4:3，则按照最大宽度来生成缩略图
            if (fWbH >= (4.0f / 3.0f))
            {
                if (_iThumbMaxWidth < iOraginalWidth)
                {
                    toWidth = _iThumbMaxWidth;
                    toHeight = (int)(toWidth * fHbW);
                }
                else//如果指定的缩略图宽度大于原图的宽度，则不生成缩略图
                {
                    toWidth = iOraginalWidth;
                    toHeight = iOraginalHeight;
                }
            }
            else//如果宽高比小于4:3，则按照最大高度来生成缩略图
            {
                if (_iThumbMaxWidth < iOraginalWidth)
                {
                    toHeight = _iThumbMaxHeight;
                    toWidth = (int)(toHeight * fWbH);
                }
                else//如果指定的缩略图高度小于原图的宽度，则不生成缩略图
                {
                    toWidth = iOraginalWidth;
                    toHeight = iOraginalHeight;
                }
            }

            System.Drawing.Image bitmap = new System.Drawing.Bitmap(toWidth, toHeight);
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);

            //设定缩略图的生成质量
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            g.Clear(System.Drawing.Color.Transparent);
            g.DrawImage(imgOraginal, new System.Drawing.Rectangle(0, 0, toWidth, toHeight), new System.Drawing.Rectangle(0, 0, iOraginalWidth, iOraginalHeight), System.Drawing.GraphicsUnit.Pixel);

            //string thumbServerPath = HttpContext.Current.Server.MapPath("缩略图路径");
            string thumbServerPath = @"VideosSL\";
            if (!Directory.Exists(thumbServerPath))
            {
                Directory.CreateDirectory(thumbServerPath);
            }
            try
            {
                bitmap.Save(thumbServerPath + "高达1(缩略图名称).jpg", System.Drawing.Imaging.ImageFormat.Jpeg);            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            finally
            {
                imgOraginal.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string strOraginalPath = @"Pictures\1.jpg";
            GetThumb(strOraginalPath);
        }