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;

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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);

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；