等比例缩放图片

 /// <summary> 
    /// 放大缩小图片尺寸 
    /// </summary> 
    /// <param name="picPath"></param> 
    /// <param name="reSizePicPath"></param> 
    /// <param name="iSize"></param> 
    /// <param name="format"></param> 
    public void PicSized(string picPath, string reSizePicPath, int iSize, ImageFormat format) 
    { 
        Bitmap originBmp = new Bitmap(picPath); 
        int w = originBmp.Width * iSize; 
        int h = originBmp.Height * iSize; 
        Bitmap resizedBmp = new Bitmap(w, h); 
        Graphics g = Graphics.FromImage(resizedBmp); 
        //设置高质量插值法   
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; 
        //设置高质量,低速度呈现平滑程度   
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 
        g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; 
        //消除锯齿 
        g.SmoothingMode = SmoothingMode.AntiAlias; 
        g.DrawImage(originBmp, new Rectangle(0, 0, w, h), new Rectangle(0, 0, originBmp.Width, originBmp.Height), GraphicsUnit.Pixel); 
        resizedBmp.Save(reSizePicPath, format); 
        g.Dispose(); 
        resizedBmp.Dispose(); 
        originBmp.Dispose(); 
    }