生成缩略图的函数代码,CSharp代码库,德仔网

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【CSharp】生成缩略图的函数
作者:阿凡卢 / 发布于2014/4/10/ 399
/// <summary>
 /// 生成缩略图
 /// </summary>
 /// <param name="originalImagePath">源图路径（物理路径）</param>
 /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
 /// <param name="width">缩略图宽度</param>
 /// <param name="height">缩略图高度</param>
 /// <param name="mode">生成缩略图的方式</param> 
 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"://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;         
     default :
       break;
   } 
   
   //新建一个bmp图片
   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(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   catch(System.Exception e)
   {
     throw e;
   }
   finally
   {
     originalImage.Dispose();
     bitmap.Dispose();           
     g.Dispose();
   }
 }
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