C#生成高清缩略图

首先是前台代码：

<div>
    <asp:FileUpload ID="photoFile" runat="server" />
    <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
    <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
</div>

然后是后台代码：

using System;
using System.Drawing;
using System.IO;
using System.Web;

namespace Shop
{
    public partial class Test : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        /// <summary>
        /// 压缩
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Button1_Click(object sender, EventArgs e)
        {
            HttpPostedFile file = photoFile.PostedFile;
            if (!file.ContentType.Contains("image"))
            {
                this.Label1.Text = "照片格式不合法";
            }
            string ext = Path.GetExtension(file.FileName).ToLower();
            if (ext != ".jpg" && ext != ".gif" && ext != ".png" && ext != ".jpeg")
            {
                this.Label1.Text = "请您上传jpg、gif、png图片";
            }
            if (file.ContentLength > 5 * 1024 * 1024)
            {
                this.Label1.Text = "请您上传512字节内的图片";
            }
            string newName = Guid.NewGuid().ToString();

            string tempPath = "upload/";

            string img = tempPath + newName + ext;

            string filePath = Server.MapPath(img);

            try
            {
                using (System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.InputStream))
                {
                    GetThumbnail(originalImage, 280, 160).Save(filePath);
                }
                this.Label1.Text = "压缩成功！";
            }
            catch (Exception ex)
            {
                
                throw ex;
            }
        }

        //---------------------------------------------为图片生成缩略图-----------------------
        /// <summary> 
        /// 为图片生成缩略图   
        /// </summary> 
        /// <param name="phyPath">原图片的路径</param> 
        /// <param name="width">缩略图宽</param> 
        /// <param name="height">缩略图高</param> 
        /// <returns></returns> 
        public System.Drawing.Image GetThumbnail(System.Drawing.Image image, int width, int height)
        {
            Bitmap bmp = new Bitmap(width, height);
            //从Bitmap创建一个System.Drawing.Graphics 
            System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);
            //设置  
            gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            //下面这个也设成高质量 
            gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            //下面这个设成High 
            gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            //把原始图像绘制成上面所设置宽高的缩小图 
            System.Drawing.Rectangle rectDestination = new System.Drawing.Rectangle(0, 0, width, height);

            gr.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height,GraphicsUnit.Pixel);

            return bmp;
        }
        //----------------------------------------------------------------------------------------
    }
}

运行效果：

最终上传（文件夹要已经存在）：

以上就是缩略图的制作。