高清方法生成缩略图函数

        /// <summary>
        /// 生成缩略图函数
        /// </summary>
        /// <param name="width">原始图片的宽度</param>
        /// <param name="height">原始图片的高度</param>
        /// <param name="left">水印字符的生成位置</param>
        /// <param name="right">水印字符的生成位置</param>
        /// <param name="picpath">原图的所在路径</param>
        /// <param name="picthumpath">生成缩略图的所在路径</param>
        public void GetThumbnailImage(int intThumbWidth, int intThumbHeight, int left, int right, string picpath, string picthumpath)
        {
            System.Drawing.Image oldimage = System.Drawing.Image.FromFile(picpath);
          
            //原图宽度和高度 
            int width = oldimage.Width;
            int height = oldimage.Height;
            int smallWidth;
            int smallHeight;

            //获取第一张绘制图的大小,(比较 原图的宽/缩略图的宽  和 原图的高/缩略图的高) 
            if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)
            {
                smallWidth = intThumbWidth + 5;
                smallHeight = intThumbWidth * height / width + 5;
            }
            else
            {
                smallWidth = intThumbHeight * width / height + 5;
                smallHeight = intThumbHeight + 5;
            }


            //新建一个图板,以最小等比例压缩大小绘制原图 
            using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))
            {
                //绘制中间图 
                using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))
                {
                    //高清,平滑 
                    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                    g.Clear(Color.Black);
                    g.DrawImage(
                    oldimage,
                    new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),
                    new System.Drawing.Rectangle(0, 0, width, height),
                    System.Drawing.GraphicsUnit.Pixel
                    );
                }
                //新建一个图板,以缩略图大小绘制中间图 
                using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))
                {
                    //绘制缩略图 
                    using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))
                    {
                        //高清,平滑 
                        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                        g.Clear(Color.Black);
                        int lwidth = (smallWidth - intThumbWidth) / 2;
                        int bheight = (smallHeight - intThumbHeight) / 2;
                        g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);
                        g.Dispose();
                        bitmap1.Save(picthumpath, System.Drawing.Imaging.ImageFormat.Jpeg);
                        bitmap1.Dispose();
                    }
                }
            }

            oldimage.Dispose();
        }