jQuery之Jcrop

头像裁剪是一个经常用到的功能，实现原理也较为简单，就是在本地选择好所需裁剪图片的坐标，将坐标发送到服务器，由服务器执行图片裁剪操作。

jQuery插件Jcrop提供了强大的图片裁剪坐标选择插件。一下来介绍它的用法。本处采用了AJAX本地上传一张图片的方法让用户裁剪。很多验证没有做，因为作为一个关于Jcrop的例子，很多验证不如与本文研究的范畴。服务器端采用MVC3实现。

直接贴代码，详解注释里面有了。

一、前台页面代码。

<link href="http://www.cnblogs.com/Content/jquery.Jcrop.css" rel="stylesheet" type="text/css" />
<script src="http://www.cnblogs.com/Content/jquery-1.7.1.js" type="text/javascript"></script>
<script src="http://www.cnblogs.com/Content/ajaxfileupload.js" type="text/javascript"></script>
<script src="http://www.cnblogs.com/Content/jquery.Jcrop.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(function () {
            $(":button").click(function () {
                //当点击上传按钮时，AJAX上传图片到服务器
                ajaxFileUpload();
            })
        })

        //当裁剪框变动时，将左上角相对图片的X坐标与Y坐标，宽度以及高度放到<input type="hidden">中(上传到服务器上裁剪会用到)
        function showCoords(c) {
            $("#p1").text(c.x + "   " + c.y + "   " + c.w + "   " + c.h );
            $("#x1").val(c.x);
            $("#y1").val(c.y);
            $("#cw").val(c.w);
            $("#ch").val(c.h);

        }

        //当AJAX上传图片操作
        function ajaxFileUpload() {
            $.ajaxFileUpload
            (
                {
                    url: '/uploadandcut/upload?action=up', //用于文件上传的服务器端请求地址up参数标记此次是上传操作还是裁剪操作
                    secureuri: false, //一般设置为false，是否安全上传
                    fileElementId: 'file1', //文件上传控件的id属性  <input type="file" id="file" name="file" />
                    dataType: 'json', //返回值类型 一般设置为json 期望服务器传回的数据类型
                    success: function (data, status)  //服务器成功响应处理函数
                    {
                        //上传成功后在将服务器上刚刚上传的图片显示在img1上
                        $("#img1").attr("src", data.imgurl);
                        if (typeof (data.error) != 'undefined') {
                            if (data.error != '') {
                                alert(data.error);
                            } else {
                                alert(data.msg);
                            }
                        }

                        //同时启动裁剪操作，触发裁剪框显示，让用户选择图片区域
                        $("#img1").Jcrop({
                            bgColor: 'black',
                            bgOpacity: .4,
                            setSelect: [100, 100, 150,150],  //设定4个角的初始位置
                            aspectRatio: 1 / 1,
                            onChange: showCoords,   //当裁剪框变动时执行的函数
                            onSelect: showCoords,   //当选择完成时执行的函数
                        });

                    },
                    error: function (data, status, e)//服务器响应失败处理函数
                    {
                        alert(e);
                    }
                }
            )
            return false;
        }
    </script>

    <div>
        <p><input type="file" id="file1" name="file" /></p>
        <input type="button" value="上传" />
        <p><img id="img1" alt="上传成功啦!" src="" /></p>
        <p id="p1"></p>

    <form id="FaceUpload" name="FaceUpload" method="post" enctype="multipart/form-data" action="/uploadandcut/Upload?action=cut">
        <input type="hidden" id="x1" name="x1" value="0" />
        <input type="hidden" id="y1" name="y1" value="0" />
        <input type="hidden" id="cw" name="cw" value="0" />
        <input type="hidden" id="ch" name="ch" value="0" />
        <input type="submit" value="裁剪上传" />
    </form>

    </div>

二、后台代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Drawing;

namespace UploadAndCut.Controllers
{
    public class UploadAndCutController : Controller
    {
        /// <summary>
        /// 打开页面
        /// </summary>
        /// <returns></returns>
        public ActionResult Index()
        {
            return View();
        }

        /// <summary>
        /// 上传操作，包括提交表单与AJAX上传图片
        /// </summary>
        /// <returns></returns>
        public ActionResult Upload()
        {
            string action = HttpContext.Request.QueryString["action"];
            //判断用户的操作类型
            switch (action.ToLower())
            {
                #region 当为上传图片操作时
                case "up":
                foreach (string upload in Request.Files)
                {
                    if (!Request.Files[upload].HasFile())
                    {
                        continue;
                    }
                    string ExtensionName = Path.GetExtension(Request.Files[upload].FileName).ToLower();
                    if (ExtensionName != ".jpg" && ExtensionName != ".png" && ExtensionName != ".gif" && ExtensionName != ".bmp")
                    {
                        return Redirect("/Tips/tip?error=您上传的图片不符合格式!");
                    }
                    string ImgPath = Server.MapPath("/uploads/" + "img" + ExtensionName);
                    Request.Files[upload].SaveAs(ImgPath);
                }
                string error = "";
                string msg = "上传成功";
                string imgurl = "/uploads/img.jpg";
                string res = "{ error:'" + error + "', msg:'" + msg + "',imgurl:'" + imgurl + "'}";
                return Content(res);
                break;
                #endregion

                #region 当为裁剪图片操作时
                case "cut":
                    string strx1 = HttpContext.Request.Form["x1"];
                    string stry1 = HttpContext.Request.Form["y1"];
                    string strcw = HttpContext.Request.Form["cw"];
                    string strch = HttpContext.Request.Form["ch"];
                    int intx1 = Convert.ToInt32(strx1);
                    int inty1 = Convert.ToInt32(stry1);
                    int intcw = Convert.ToInt32(strcw);
                    int intch = Convert.ToInt32(strch);

                    Stream imgStream = GetLocalStream(Server.MapPath("/uploads/" + "img.jpg"));
                    //System.Drawing.Image initImage = System.Drawing.Image.FromStream(imgStream);
                    Cut(imgStream, Server.MapPath("/uploads/img.jpg"), intx1, inty1, intcw, intch, 100);
                    return Redirect("/uploadandcut/index");
                break;
                #endregion

                default:
                    return null;
                break;
            }
        }

        /// <summary>
        /// 将一个文件读成字符流
        /// </summary>
        /// <param name="InFilePath"></param>
        /// <returns></returns>
        public static Stream GetLocalStream(string InFilePath)
        {
            return new MemoryStream(ReadFileReturnBytes(InFilePath));
        }

        /// <summary>从文件中读取二进制数据</summary>
        /// <param name="filePath">文件路径</param>
        /// <returns> byte[]二进制数据</returns>
        public static byte[] ReadFileReturnBytes(string filePath)
        {
            FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
            BinaryReader br = new BinaryReader(fs);
            byte[] buff = br.ReadBytes((int)fs.Length);
            br.Close();
            fs.Close();
            return buff;
        }

        #region 裁剪操作
        public static void Cut(System.IO.Stream fromFile, string fileSaveUrl, int xPosition, int yPosition, int width, int height, int quality)
        {
            //创建目录
            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
            System.Drawing.Image initImage = System.Drawing.Image.FromStream(fromFile, true);
            //原始图片的宽、高
            int initWidth = initImage.Width;
            int initHeight = initImage.Height;
            if (xPosition + width > initWidth)
                width = initWidth - xPosition;
            if (yPosition + height > initHeight)
                height = initHeight - yPosition;
            //与原图相等直接保存
            if ((width >= initWidth && height >= initHeight) || (width < 1 && height < 1))
            {
                initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            else
            {
                System.Drawing.Image pickedImage = null;
                System.Drawing.Graphics pickedG = null;
                //对象实例化
                pickedImage = new System.Drawing.Bitmap(width, height);
                pickedG = System.Drawing.Graphics.FromImage(pickedImage);
                //设置质量
                pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                //定位
                System.Drawing.Rectangle fromR = new System.Drawing.Rectangle(xPosition, yPosition, width, height);
                System.Drawing.Rectangle toR = new System.Drawing.Rectangle(0, 0, width, height);
                //画图
                pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);
                //关键质量控制
                //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
                System.Drawing.Imaging.ImageCodecInfo[] icis = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders();
                System.Drawing.Imaging.ImageCodecInfo ici = null;
                foreach (System.Drawing.Imaging.ImageCodecInfo i in icis)
                {
                    if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")
                    {
                        ici = i;
                    }
                }
                System.Drawing.Imaging.EncoderParameters ep = new System.Drawing.Imaging.EncoderParameters(1);
                ep.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);
                //保存缩略图
                pickedImage.Save(fileSaveUrl, ici, ep);
                //释放关键质量控制所用资源
                ep.Dispose();
                //释放截图资源
                pickedG.Dispose();
                pickedImage.Dispose();
                //释放原始图片资源
                initImage.Dispose();
            }
        }
        #endregion
    }
}

还有一个扩展方法，在DEMO里面会有，不粘贴了。DEMO下载地址