动态生成缩略图

Util.cs 的部分代码：

//// <summary>
/// 创建缩略图
/// </summary>
/// <param name="src">来源页面
/// 可以是相对地址或者绝对地址
/// </param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <returns>字节数组</returns>
public static byte[] MakeThumbnail(string src, double width, double height)
{
    Image image;

    // 相对路径从本机直接读取
    if (src.ToLower().IndexOf("http://") == -1)
    {
        src = HttpContext.Current.Server.MapPath(src);
        image = Image.FromFile(src, true);
    }
    else // 绝对路径从 Http 读取
    {
        HttpWebRequest req = (HttpWebRequest) WebRequest.Create(src);
        req.Method = "GET";
        HttpWebResponse resp = (HttpWebResponse) req.GetResponse();
        Stream receiveStream = resp.GetResponseStream();
        image = Image.FromStream(receiveStream);
        resp.Close();
        receiveStream.Close();
    }
    double newWidth, newHeight;
    if (image.Width > image.Height)
    {
        newWidth = width;
        newHeight = image.Height*(newWidth/image.Width);
    }
    else
    {
        newHeight = height;
        newWidth = (newHeight/image.Height)*image.Width;
    }
    if (newWidth > width)
    {
        newWidth = width;
    }
    if (newHeight > height)
    {
        newHeight = height;
    }
    //取得图片大小
    Size size = new Size((int) newWidth, (int) newHeight);
    //新建一个bmp图片
    Image bitmap = new Bitmap(size.Width, size.Height);
    //新建一个画板
    Graphics g = Graphics.FromImage(bitmap);
    //设置高质量插值法
    g.InterpolationMode = InterpolationMode.High;
    //设置高质量,低速度呈现平滑程度
    g.SmoothingMode = SmoothingMode.HighQuality;
    //清空一下画布
    g.Clear(Color.White);
    //在指定位置画图
    g.DrawImage(image, new Rectangle(0, 0, bitmap.Width, bitmap.Height),
                new Rectangle(0, 0, image.Width, image.Height),
                GraphicsUnit.Pixel);
    ////文字水印
    //System.Drawing.Graphics G=System.Drawing.Graphics.FromImage(bitmap);
    //System.Drawing.Font f=new Font("宋体",10);
    //System.Drawing.Brush b=new SolidBrush(Color.Black);
    //G.DrawString("myohmine",f,b,10,10);
    //G.Dispose();
    ////图片水印
    //System.Drawing.Image copyImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath("pic/1.gif"));
    //Graphics a = Graphics.FromImage(bitmap);
    //a.DrawImage(copyImage, new Rectangle(bitmap.Width-copyImage.Width,bitmap.Height-copyImage.Height,copyImage.Width, copyImage.Height),0,0, copyImage.Width, copyImage.Height, GraphicsUnit.Pixel);
    //copyImage.Dispose();
    //a.Dispose();
    //copyImage.Dispose();
    //保存高清晰度的缩略图
    MemoryStream stream = new MemoryStream();
    bitmap.Save(stream, ImageFormat.Jpeg);
    byte[] buffer = stream.GetBuffer();
    g.Dispose();
    image.Dispose();
    bitmap.Dispose();
    return buffer;
}