在 .net 中怎样对图片实现等比缩放？

Question

如何在C#中实现图片缩放
http://www.z6688.com/info/34815-1.htm

Answer 1

请看视频:
http://download.csdn.net/source/321082

Answer 2

public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
  {
   WebRequest wr=WebRequest.Create(originalImagePath);
   WebResponse res=wr.GetResponse(); 
   System.Drawing.Image originalImage =  System.Drawing.Image.FromStream(res.GetResponseStream());
   //System.Drawing.Image.FromFile(originalImagePath);
    //originalImagePath 来源路径
    //thumbnailPath 目的路径
    //width 源图片宽
    //height 源图片高
    //mode 缩放模式
            
   int towidth = width;
   int toheight = height;
       
   int x = 0;
   int y = 0;
   int ow = originalImage.Width;
   int oh = originalImage.Height;          switch (mode)
   {       
    case "HW"://指定高宽缩放（可能变形）               
     break;
    case "W"://指定宽，高按比例                   
     toheight = originalImage.Height * width/originalImage.Width;
     break;
    case "H"://指定高，宽按比例
     towidth = originalImage.Width * height/originalImage.Height;                   
     break;       
    case "Cut"://指定高宽裁减（不变形）               
     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;
    case "D":
     if((double)originalImage.Width>(double)originalImage.Height)
     {
      toheight = originalImage.Height * width/originalImage.Width;
     }
     else
     {
      towidth = originalImage.Width * height/originalImage.Height;
     }
     break;
    default :
     break;
   }   
           
   //新建一个bmp图片
   System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth,toheight);   //新建一个画板
   Graphics g = System.Drawing.Graphics.FromImage(bitmap);   //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;   //清空画布并以透明背景色填充
   g.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
   g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
    new Rectangle(x, y, ow,oh),
    GraphicsUnit.Pixel);   try
   {           
    //以jpg格式保存缩略图
    bitmap.Save( Server.MapPath(".")+"\\"+thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   catch(System.Exception e)
   {
    throw e;
   }
   finally
   {
    originalImage.Dispose();
    bitmap.Dispose();                       
    g.Dispose();
   }
  } 

Answer 3

http://www.cnblogs.com/xmg1982/articles/1202241.html
http://www.cnblogs.com/aqiang/articles/1188728.html

Answer 4

http://blog.csdn.net/ojekleen/archive/2008/08/01/2754255.aspx