.net实现裁剪网站上传图片的方法

本文实例讲述了基于.net实现裁剪网站上传图片的方法。由于客户端javascript不能操作文件，所以只能先上传图片再在服务器端剪切。
1、上传图片
2、javascript剪切图片（其实只是选取要剪切的部分）
3、服务器端剪切
 
（1）在页面的cs文件中剪切。须放几个隐藏控件以便回传js选取的坐标。

其中剪切图片源码如下：

using system;  
using system.collections.generic;  
using system.text;  
using system.drawing;  
 
public class cut  
{  
  /// <summary>  
  /// 裁剪图片  
  /// </summary>  
  /// <param name="sourceimg">原图片路径</param>  
  /// <param name="desimg">裁剪图片路径</param>  
  /// <param name="left">x</param>  
  /// <param name="top">y</param>  
  /// <param name="width">宽</param>  
  /// <param name="height">高</param>  
  public static void cutimage(string sourceimg, string desimg, int left, int top, int width, int height)  
  {  
    system.drawing.image img = system.drawing.bitmap.fromfile(sourceimg);  
    system.drawing.image imgtosave = new system.drawing.bitmap(width, height);  
    system.drawing.graphics g = system.drawing.graphics.fromimage(imgtosave);  
    rectanglef sourcerect = new rectanglef(left, top, width, height);  
    rectanglef destinationrect = new rectanglef(0, 0, width, height);  
 
    g.drawimage(img,  
          destinationrect,  
          sourcerect,  
          graphicsunit.pixel  
          );  
    g.save();  
    imgtosave.save(desimg, system.drawing.imaging.imageformat.jpeg);  
    g.dispose();  
    imgtosave.dispose();  
    img.dispose();  
  }  
 
 
}  

（2）在ashx中剪切，可回传文件流。用参数传递坐标。   

using system;  
using system.web;  
using system.drawing;  
using system.io;  
 
public class imgcropper_webhandler : ihttphandler  
{  
  public void processrequest(httpcontext context)  
  {  
    string pic = convert.tostring(context.request["p"]);  
    int pointx = convert.toint32(context.request["x"]);  
    int pointy = convert.toint32(context.request["y"]);  
    int cutwidth = convert.toint32(context.request["w"]);  
    int cutheight = convert.toint32(context.request["h"]);  
    int picwidth = convert.toint32(context.request["pw"]);  
    int picheight = convert.toint32(context.request["ph"]);  
 
    context.response.contenttype = "image/jpeg";  
    resetimg(context, system.web.httpcontext.current.server.mappath(pic), picwidth, picheight, pointx, pointy, cutwidth, cutheight).writeto(context.response.outputstream);  
  }  
 
  public memorystream resetimg(httpcontext context, string imgfile, int picwidth, int picheight, int pointx, int pointy, int cutwidth, int cutheight)  
  {  
    image imgphoto = image.fromfile(imgfile);  
    bitmap bmphoto = new bitmap(cutwidth, cutheight, system.drawing.imaging.pixelformat.format24bpprgb);  
 
    graphics gbmphoto = graphics.fromimage(bmphoto);  
    gbmphoto.drawimage(imgphoto, new rectangle(0, 0, cutwidth, cutheight), pointx * imgphoto.width / picwidth, pointy * imgphoto.height / picheight, cutwidth * imgphoto.width / picwidth, cutheight * imgphoto.height / picheight, graphicsunit.pixel);  
 
    //保存图片到服务器  
    bmphoto.save(context.server.mappath("upload/") + guid.newguid() + ".jpg", system.drawing.imaging.imageformat.jpeg);  
 
    //生成文件流回传  
    memorystream ms2 = new memorystream();  
    bmphoto.save(ms2, system.drawing.imaging.imageformat.jpeg);  
 
    imgphoto.dispose();  
    gbmphoto.dispose();  
    bmphoto.dispose();  
 
    return ms2;  
  }  
 
 
  public bool isreusable  
  {  
    get 
    {  
      return false;  
    }  
  }  
}