asp.net显示高清缩略图

如题：

 

添加命名空间如下：

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

-----------------------------------------------------------------------------------------------

 

显示原图：

//显示原图 protected void btnImage_Click(object sender, EventArgs e) { string filePath = Server.MapPath("~/Up/美女.jpg"); //方式一： //Response.ContentType = "image/jpeg"; //Response.WriteFile(filePath); //方式二： FileStream imageStr = new FileStream(filePath, FileMode.Open); byte[] imageData=new byte[imageStr.Length]; imageStr.Read(imageData,0,(int)imageStr.Length); Response.OutputStream.Write(imageData, 0, (int)imageStr.Length); }

 

想要改变的尺寸：

private static Size NewSize(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)//如果maxWidth和maxHeight大于源图像，则缩略图的长和高不变 { 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 Size(Convert.ToInt32(w), Convert.ToInt32(h)); }

 

转化成缩略图：

 

//转化成缩略图 public void SendSmallImage(string filename, string newfile, int maxHeight, int maxWidth) { System.Drawing.Image img = System.Drawing.Image.FromFile(filename);//源图像的信息 System.Drawing.Imaging.ImageFormat thisformat = img.RawFormat; //源图像的格式 Size newSize = NewSize(maxWidth, maxHeight, img.Width, img.Height); //返回调整后的图像Width与Height Bitmap outBmp = new Bitmap(newSize.Width, newSize.Height); Graphics g = Graphics.FromImage(outBmp); //设置画布的描绘质量(高) g.CompositingQuality = CompositingQuality.HighQuality; g.SmoothingMode = SmoothingMode.HighQuality; g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(img, new Rectangle(0, 0, newSize.Width, newSize.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel); g.Dispose(); //以下代码为保存图片时，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; //获取包含有关内置图像编码解码器的信息的ImageCodecInfo对象。 ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders(); ImageCodecInfo jpegICI = null; for (int x = 0; x < arrayICI.Length; x++) { if (arrayICI[x].FormatDescription.Equals("JPEG")) { jpegICI = arrayICI[x];//设置jpeg编码 break; } } if (jpegICI != null) { outBmp.Save(newfile , jpegICI, encoderParams); } else { outBmp.Save(newfile, thisformat); } img.Dispose(); outBmp.Dispose(); }

 

页面上是一个FileUpload控件，先上传原图，在显示在页面上，添加一个Image控件，宽，高设为：100×100，用以对比缩略图。

将原图输出缩略为100×100；