.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;
    }
  }
}