using System;
using System.Drawing;
using System.Drawing.Imaging;namespace Demo.Web
{public partial class GetThumbnail : System.Web.UI.Page{protected void Page_Load(object sender, EventArgs e){Response.Clear();string originalFileName =Server.MapPath( Request.QueryString["imgSrc"]);int thumbnailWidth = Convert.ToInt32(Request.QueryString["width"]);int thumbnailHeight = Convert.ToInt32(Request.QueryString["height"]);System.Drawing.Image img = System.Drawing.Image.FromFile(originalFileName);var thisFormat = img.RawFormat;System.Drawing.Size newSize = GetNewSize(thumbnailWidth, thumbnailHeight, img.Width, img.Height);var outBmp = new System.Drawing.Bitmap(thumbnailWidth, thumbnailHeight);var g = System.Drawing.Graphics.FromImage(outBmp);//设置画布的描绘质量g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;g.Clear(System.Drawing.Color.FromArgb(255, 249, 255, 240));//.Transparent);//.FromArgb(255, 249, 255, 240));g.DrawImage(img, new Rectangle((thumbnailWidth - newSize.Width) / 2,(thumbnailHeight - newSize.Height) / 2,newSize.Width, newSize.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel);g.Dispose();if (thisFormat == System.Drawing.Imaging.ImageFormat.Gif){Response.ContentType = "image/gif";}else{Response.ContentType = "image/jpeg";} // 设置压缩质量     EncoderParameters encoderParams = new EncoderParameters();long[] quality = new long[1];quality[0] = 100;EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);encoderParams.Param[0] = encoderParam;//获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。var arrayICI = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders();System.Drawing.Imaging.ImageCodecInfo jpegICI = null;for (int fwd = 0; fwd < arrayICI.Length; fwd++){if (arrayICI[fwd].FormatDescription.Equals("JPEG")){jpegICI = arrayICI[fwd];break;}}if (jpegICI != null)outBmp.Save(Response.OutputStream, jpegICI, encoderParams);elseoutBmp.Save(Response.OutputStream, img.RawFormat);}private Size GetNewSize(int maxWidth, int maxHeight, int width, int height){double w = 0.0;double h = 0.0;double sw = Convert.ToDouble(width);double sh = Convert.ToDouble(height);double mw = Convert.ToDouble(maxWidth);double mh = Convert.ToDouble(maxHeight);if (sw < mw && sh < mh){w = sw;h = sh;}else if ((sw / sh) > (mw / mh)){w = maxWidth;h = (w * sh) / sw;}else{h = maxHeight;w = (h * sw) / sh;}return new System.Drawing.Size(Convert.ToInt32(w), Convert.ToInt32(h));}}
}

<img alt='' border="0" src='GetThumbnail.aspx?imgsrc=<%#Eval("ImgUrl") %>&width=300&height=300' />