更改图片大小

Question

怎样用C#程序写一个能改变图片大小的程序，！！！
谢谢！！！！

Answer 1

  #region 图片上传
    ///<summary>
    ///方法名称：upLogd
    ///内容摘要：图片上传
    /// </summary>
    /// <param name="path">源图路径（物理路径） </param>
    /// <param name="spath">缩略图路径（物理路径） </param>
    /// <param name="fu">图片上传控件 </param>
    /// <param name="w">缩略图宽度 </param>
    /// <param name="h">缩略图高度 </param>
    public string upLoad(string Path, string sPath, FileUpload fu, int w, int h)
    {        //判断上传控件中是否有值
        if (fu.HasFile == false)
        {
            return "请选择要上传的图片!";
        }
        else
        {
            string fType = fu.PostedFile.ContentType;//获取图像的类型
            if (fType == "image/bmp" || fType == "image/gif" || fType == "image/pjpeg" || fType == "image/jpeg" || fType == "image/x-png")
            {                //获取文件信息
                FileInfo file = new FileInfo(fu.PostedFile.FileName);                System.DateTime currentTime = new System.DateTime();
                currentTime = DateTime.Now;
                string stamp = currentTime.Year.ToString() + currentTime.Month.ToString() + currentTime.Day.ToString() + currentTime.Hour.ToString() + currentTime.Minute.ToString() + currentTime.Second.ToString() + currentTime.Millisecond.ToString();                //原始图片保存路径
                string path = Path + stamp + ".gif";
                //缩略图保存路径
                string spath = sPath + "Thumb_" + stamp + ".gif";
                try
                {                    //原始图片保存
                    fu.SaveAs(path);
                    //缩略图保存
                    if (w != 0 && h != 0)
                    {
                        MakeThumbImage(path, spath, w, h);
                    }
                    return "图片上传成功|" + stamp + ".gif";
                }
                catch(Exception ex)
                {
                    return "图片上传失败"+ex.Message.ToString();
                }
            }
            else
            {
                return "上传图片格式不正确!请上传jpg/jpge/gif/bmp/png格式的图片!";
            }
        }
    } 
    #endregion    #region 图片压缩
    /// <summary>
    ///方法名称：MakeThumbImage
    ///内容摘要：生成缩略图
    /// </summary>
    /// <param name="sPath">源图路径（物理路径） </param>
    /// <param name="stPath">缩略图路径（物理路径） </param>
    /// <param name="nWidth">缩略图宽度 </param>
    /// <param name="nHeight">缩略图高度 </param>
    private void MakeThumbImage(string sPath, string stPath, int nWidth, int nHeight)
    {
        System.Drawing.Image sImage = System.Drawing.Image.FromFile(sPath);
        int tw = nWidth;
        int th = nHeight;
        ///原始图片的宽度和高度
        int sw = sImage.Width;
        int sh = sImage.Height;
        if (sw > tw)
        {
            sw = tw;
        }
        if (sh > th)
        {
            sh = th;
        }
        System.Drawing.Bitmap objPic, objNewPic;
        objPic = new System.Drawing.Bitmap(sPath);
        objNewPic = new System.Drawing.Bitmap(objPic, sw, sh);
        objNewPic.Save(stPath);
        sImage.Dispose();
        objPic.Dispose();
        objNewPic.Dispose();
    }    #endregion

Answer 2

图片缩略图
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
  {
  Image originalImage = Image.FromFile(originalImagePath);
  int towidth = width;
  int toheight = height;
  int x = 0;
  int y = 0;
  int ow = originalImage.Width;
  int oh = originalImage.Height;   
  switch (mode)
  {   
  case "HW":   
  break;
  case "W":   
  toheight = originalImage.Height * width/originalImage.Width;
  break;
  case "H":
  towidth = originalImage.Width * height/originalImage.Height;   
  break;   
  case "Cut":   
  if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight)
  {
  oh = originalImage.Height;
  ow = originalImage.Height*towidth/toheight;
  y = 0;
  x = (originalImage.Width - ow)/2;
  }
  else
  {
  ow = originalImage.Width;
  oh = originalImage.Width*height/towidth;
  x = 0;
  y = (originalImage.Height - oh)/2;
  }
  break;   
  default :
  break;
  }   
  Image bitmap = new System.Drawing.Bitmap(towidth,toheight);
  Graphics g = System.Drawing.Graphics.FromImage(bitmap);
  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
  g.Clear(Color.Transparent);   
  g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),  
  new Rectangle(x, y, ow,oh),
  GraphicsUnit.Pixel);  try
  {   
  bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
  }
  catch(System.Exception e)
  {
  throw e;
  }
  finally
  {
  originalImage.Dispose();
  bitmap.Dispose();   
  g.Dispose();
  }
  }