C#简单生成缩略图的方法

本文实例讲述了c#简单生成缩略图的方法。分享给大家供大家参考。具体实现方法如下：

/// <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();
 }
}

希望本文所述对大家的c#程序设计有所帮助。