图片控制

using System.Drawing; //导入命名空间 

//FileUpload 图片上传空间的ID
        string postedfile = this.FileUpload.PostedFile.FileName;
        string filePic = "";
        string filePicSimple = "";
        if (!(null == postedfile || "" == postedfile))
        {

System.IO.Stream stream=this.FileUpload.PostedFile.InputStream;
        System.Drawing.Image tempimg = System.Drawing.Image.FromStream(stream);
        int width = tempimg.Width;//图片宽
        int height = tempimg.Height;//图片的高
        //--------
        int iwidth = 160; //定义允许图片宽度，当宽度大于这个值时等比例缩小
        int iheight = 120; //定义允许图片高度，当高度大于这个值时等比例缩小
        int width2 = width;  //临时的高
        int height2 = height; //临时的宽
        if (width2 > 0 && height2 > 0)
        {
            if (width2 / height2 >= iwidth / iheight)
            {
                if (width2 > iwidth)
                {
                    width = iwidth;
                    height = (height2 * iwidth) / width2;
                }
                else
                {
                    width = width2;
                    height = height2;
                }
            }
            else
            {
                if (height2 > iheight)
                {
                    height = iheight;
                    width = (width2 * iheight) / height2;
                }
                else
                {
                    width = width2;
                    height = height2;
                }
            }
        }
        //--------
            string extension = System.IO.Path.GetExtension(postedfile);
            string Guidname = Convert.ToString(Guid.NewGuid());
            filePic = Guidname + extension;
            filePicSimple = Guidname + "small" + extension;
            this.FileUpload.PostedFile.SaveAs(Server.MapPath("upload/" + filePic));

            System.Drawing.Image oldimage = System.Drawing.Image.FromFile(Server.MapPath("upload/") + filePic);
            System.Drawing.Image thumbnailImage = oldimage.GetThumbnailImage(width, height, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);
            Bitmap output = new Bitmap(thumbnailImage);
            Graphics g = Graphics.FromImage(output);
            output.Save(Server.MapPath("upload/") + filePicSimple, System.Drawing.Imaging.ImageFormat.Jpeg);
            Response.Write("<script>alert('成功');window.history.go(-1);</script>");
        }

//在加一个方法 
 bool ThumbnailCallback()
    {
        return true;
    }