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;
}
}
}
