图片缩小后再放大，然后就变得很模糊了，请问怎么办
如题，我缩小放大是直接改变图片长宽的。。。

[解决办法]

C# code

HttpPostedFile upPhoto = photo.PostedFile;                    int upPhotoLength = upPhoto.ContentLength;                    System.Drawing.Image oldImage, newImage; //存放老图和新图                    int imageLength = 60; //60k                    int imageSize = 400;                    if (upPhotoLength > imageLength * 1024)                    {                        //调整图片大小                        oldImage = System.Drawing.Image.FromStream(upPhoto.InputStream);                        newImage = Helper.ThumbnailImage(oldImage, imageSize);                    }                    else                    {                        newImage = System.Drawing.Image.FromStream(upPhoto.InputStream);                    }                    MemoryStream PhotoStream = new MemoryStream();                    newImage.Save(PhotoStream, System.Drawing.Imaging.ImageFormat.Jpeg);
[解决办法]
缩小图重新生成别覆盖原图吧
就像一般网站上图片新闻什么的,根据大图生成一张小的缩略图
[解决办法]
C# code
public static System.Drawing.Image ThumbnailImage(System.Drawing.Image oldImage, int newSize)    {        decimal width = oldImage.Width;        decimal height = oldImage.Height;        int newwidth, newheight;        if (width > height)        {            newwidth = newSize;            newheight = (int)(height / width * newSize);        }        else        {            newheight = newSize;            newwidth = (int)(width / height * newSize);        }        return oldImage.GetThumbnailImage(newwidth, newheight, null, IntPtr.Zero);    }
[解决办法]
这是肯定的。缩小图片信息量就减少了。否则还要图像压缩算法干什么。