1.生成縮圖的主要程式碼

        /// <summary>
        /// 圖片顯示成縮圖
        /// </summary>
        /// <param name="sourcePath" >圖片原路徑</param>
        /// <param name="newPath">生成的縮圖新路徑</param>
        /// <param name="width">生成的縮圖寬度</param>
        /// <param name="height">生成的縮圖高度</param>
        public static void MakeThumbnail(string sourcePath, string newPath, int width, int height)
        {
            sourcePath = System.Web
 
.HttpContext.Current.Server.MapPath(sourcePath);
            newPath = System.Web.HttpContext.Current.Server.MapPath(newPath);
            System.Drawing.Image ig = System.Drawing.Image.FromFile(sourcePath);
            int towidth = width;
            int toheight = height;
            int x = 0;
            int y
 
 = 0;
            int ow = ig.Width;
            int oh = ig.Height;
            if ((double)ig.Width / (double)ig.Height > (double)towidth / (double)toheight)
            {
                oh = ig.Height;
                ow = ig.Height * towidth / toheight;
                y = 0;
                x = (ig.Width
 
 - ow) / 2;

            }
            else
            {
                ow = ig.Width;
                oh = ig.Width * height / towidth;
                x = 0;
                y = (ig.Height - oh) / 2;
            }
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.Clear(System.Drawing.Color.Transparent);
            g.DrawImage(ig, new System.Drawing.Rectangle(0, 0, towidth, toheight), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
            try
            {
                bitmap.Save(newPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                ig.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

2.具體操作流程
1.` protected void Page_Load(object sender, EventArgs e)
{
if (File.Exists(Server.MapPath(“現有圖片路徑”.ToString())))//判斷現有圖片路徑是否存在
{
S_ImageHelper.MakeThumbnail(“現有圖片路徑”.ToString(), “新建縮圖路徑”, 275, 254);
}

        Response.Write("成功");
}`

3。顯示成功，則縮圖生成好了，去看看你的新建路徑裡面是否又該圖片吧