.net 生成缩略图

public static void CreateSmallImage(string minImageFullPath, System.Drawing.Image originalImage, int x, int y, int size)
    {
        System.Drawing.Image img = null;
        System.Drawing.Graphics graphic = null;

        int ow = originalImage.Width;
        int oh = originalImage.Height;
        int width;
        int height;
　　　　 //最小边宽度为size,按比例生成
        if (ow > oh)
        {
            height = size;
            width = size * ow / oh;
            
        }
        else
        {
            width = size;
            height = size * oh / ow;
        }
        img = new System.Drawing.Bitmap(width, height);
        graphic = System.Drawing.Graphics.FromImage(img);
        graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

        //设置高质量,低速度呈现平滑程度
        graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        //清空画布并以透明背景色填充
        graphic.Clear(Color.Transparent);

        //在指定位置并且按指定大小绘制原图片的指定部分ImageFormat.Jpeg
        graphic.DrawImage(originalImage, new Rectangle(0, 0, width, height), new Rectangle(x, y, ow, oh), GraphicsUnit.Pixel);

　　　　 //默认保存格式为ImageFormat.Png图片还是比较大，所以存为ImageFormat.Jpeg格式

        img.Save(minImageFullPath,ImageFormat.Jpeg);
        if (img != null)
        {
            img.Dispose();
        }
        if (graphic != null)
        {
            graphic.Dispose();
        }
    }

OriginalImage 参数

System.Drawing.Image image = System.Drawing.Image.FromFile(originalImagePath);
//或 HttpPostedFile file= Request.Files["Filedata"];
//System.Drawing.Image image = System.Drawing.Image.FromStream(file.InputStream);
CreateSmallImage(minFilePath, image, 0, 0, 160);