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;

 

 



版权声明:本文为博主原创文章,未经博主允许不得转载。