ASP.NET Ajax实现图片剪裁

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ASP.NET
JS

实现这个功能主要用到了JQuery和基于JQuery的图片处理插件JCrop。

JQuery可以下载下来，或者在代码中这样引用<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>。
JCrop需要下载，其中还包括相应的一些例子可以作为参考。

这个例子有三部分功能，一、图片上传，二、现实用户上传上来的图片，三、图片剪裁。
主要的流程是：用户上传图片，显示图片，在用户点击剪裁按钮之后，用ajax的方式显示剪裁之后的图片。
上传图片就用的ASP.NET自带的文件上传控件，整个文件上传功能放在一个用户空间里面。
每次用户上传了图片以后，文件存放的位置持久化在一个xml文件中。
在用JCrop实现剪裁功能的时候，需要在页面中添加一些隐藏域来
存储图片剪裁中用到的坐标和宽高等数据。剪裁则用JQuery的Ajax功能实现。

1 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Pages_Default" %>
2
3 <%@ Register Src="../Controls/ImageUpload.ascx" TagName="ImageUpload" TagPrefix="uc1" %>
4 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
5 <html xmlns="http://www.w3.org/1999/xhtml">
6 <head runat="server">
7     <title></title>
8
9     <script src="../Scripts/jquery.min.js" type="text/javascript"></script>
10
11     <script src="../Scripts/jquery.Jcrop.js" type="text/javascript"></script>
12
13     <link href="../Style/jquery.Jcrop.css" rel="stylesheet" type="text/css" />
14     <link href="../Style/demos.css" rel="stylesheet" type="text/css" />
15
16     <script type="text/javascript" language="Javascript">
17
18         // Remember to invoke within jQuery(window).load()
19         // If you don't, Jcrop may not initialize properly
20         jQuery(document).ready(function() {
21
22             jQuery('#cropbox').Jcrop({
23                 //onChange: showCoords,
24                 onSelect: showCoords
25             });
26
27         });
28
29         function onCropClick() {
30
31             //alert("{ pPartStartPointX: '" + $('#x').val() + "', pPartStartPointY: '" + $('#y').val() + "', pPartWidth: '" + $('#w').val() + "', pPartHeight: '" + $('#h').val() + "'}");
32             $.ajax({
33                 type: "POST",
34                 contentType: "application/json; charset=utf-8",
35                 data: "{ pPartStartPointX: '" + $('#x').val() + "', pPartStartPointY: '" + $('#y').val() + "', pPartWidth: '" + $('#w').val() + "', pPartHeight: '" + $('#h').val() + "'}",
36                 url: "Default.aspx/CroppedImage",
37                 dataType: "json",
38                 success: function(data) {
39                     //alert(data.d);
40                     //$("#CustomerDetails").html(data);
41                     $('#disp').html("<img src='" + data.d + "' alt='' />");
42                 }
43             });
44         }
45
46         // Our simple event handler, called from onChange and onSelect
47         // event handlers, as per the Jcrop invocation above
48         function showCoords(c) {
49             jQuery('#x').val(c.x);
50             jQuery('#y').val(c.y);
51             //jQuery('#x2').val(c.x2);
52             //jQuery('#y2').val(c.y2);
53             jQuery('#w').val(c.w);
54             jQuery('#h').val(c.h);
55         };
56
57     </script>
58
59 </head>
60 <body>
61     <form id="form1" runat="server">
62     <div>
63         
64         <img runat="server" id="cropbox" />
65         <input type="button" id="btnCrop" value=" Crop Image " onclick="onCropClick();" />
66         <div id="disp">
67         </div>
68         <label>
69             <%--X1--%>
70             <input type="hidden" size="4" id="x" name="x" /></label>
71         <label>
72             <%--Y1--%>
73             <input type="hidden" size="4" id="y" name="y" /></label>
74         <label>
75             <%--X2--%>
76             <input type="hidden" size="4" id="x2" name="x2" /></label>
77         <label>
78             <%--Y2--%>
79             <input type="hidden" size="4" id="y2" name="y2" /></label>
80         <label>
81             <%--W--%>
82             <input type="hidden" size="4" id="w" name="w" /></label>
83         <label>
84             <%--H--%>
85             <input type="hidden" size="4" id="h" name="h" /></label>
86         <uc1:ImageUpload ID="ImageUpload1" runat="server" />
87     </div>
88     </form>
89 </body>
90 </html>

注意在页面代码中添加需要的javascript和css样式表

1<script src="../Scripts/jquery.min.js" type="text/javascript"></script>
2<script src="../Scripts/jquery.Jcrop.js" type="text/javascript"></script>
3<link href="../Style/jquery.Jcrop.css" rel="stylesheet" type="text/css" />
4<link href="../Style/demos.css" rel="stylesheet" type="text/css" />

然后我们需要添加调用JCrop的代码来实现图片的剪裁

1    <script type="text/javascript" language="Javascript">
2
3        jQuery(document).ready(function() {
4
5            jQuery('#cropbox').Jcrop({
6                onSelect: showCoords
7            });
8        });
9
10        function onCropClick() {
11
12            $.ajax({
13                type: "POST",
14                contentType: "application/json; charset=utf-8",
15                data: "{ pPartStartPointX: '" + $('#x').val() + "', pPartStartPointY: '" + $('#y').val() + "', pPartWidth: '" + $('#w').val() + "', pPartHeight: '" + $('#h').val() + "'}",
16                url: "Default.aspx/CroppedImage",
17                dataType: "json",
18                success: function(data) {
19                    $('#disp').html("<img src='" + data.d + "' alt='' />");
20                }
21            });
22        }
23
24        function showCoords(c) {
25            jQuery('#x').val(c.x);
26            jQuery('#y').val(c.y);
27            jQuery('#w').val(c.w);
28            jQuery('#h').val(c.h);
29        };
30
31    </script>

这个代码都很简单。JCrop处理id为cropbox的img中的图片。在onSelect事件中添加函数showCoords来记录用户选中图片区域的数据。
并在剪裁按钮的点击事件中实现Ajax的功能，将后台处理好的图片显示在页面上。

所需的命名空间

1using System;
2using System.Web;
3using System.Web.Services;

为什么要用System.Web.Services这个命名空间呢，因为我们用JQuery调用后台代码时用的是后台的页面方法

1    [WebMethod]
2    public static string CroppedImage(int pPartStartPointX, int pPartStartPointY, int pPartWidth, int pPartHeight)
3    {
4        XmlHelper xmlHelper = new XmlHelper();
5        xmlHelper.XmlPath = HttpContext.Current.Server.MapPath("~/App_Data/ImagePaths.xml");
6        string originalPath = xmlHelper.GetImagepath();
7        string savePath = HttpContext.Current.Server.MapPath("~/Images/CropImg/");
8        string filename = ImageHelper.CropImage(originalPath, savePath, pPartWidth, pPartHeight, pPartStartPointX, pPartStartPointY);
9
10        string fullpath = "../Images/CropImg/" + filename;
11        return fullpath;
12    }

前面提到过用户控件，上传图片并记录图片的存放路径。存放图片路径主要通过类XmlHelper来实现。

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="ImageUpload.ascx.cs" Inherits="Controls_ImageUpload" %>
<%--<asp:PlaceHolder ID="imageContainer" runat="server"></asp:PlaceHolder>--%>
<table>
    <tr>
        <td>
            <asp:FileUpload ID="imgUpload" runat="server" />
        </td>
    </tr>
    <tr>
        <td>
            <asp:Button ID="btnUpload" runat="server" Text=" Up Load "
                onclick="btnUpload_Click" />
        </td>
    </tr>
</table>

后台代码

1using System;
2using System.Web.UI.HtmlControls;
3
4public partial class Controls_ImageUpload : System.Web.UI.UserControl
5{
6    private readonly string IMG_PATH = "~/Images/Upload/";
7    private XmlHelper _xmlHelper = new XmlHelper();
8
9    /// <summary>
10    /// Name of a control to operate
11    /// </summary>
12    public string ControlName { get; set; }
13
14    protected void Page_Load(object sender, EventArgs e)
15    {
16        if (!IsPostBack)
17        {
18            SetPathInfo();
19        }
20    }
21
22    protected void btnUpload_Click(object sender, EventArgs e)
23    {
24        try
25        {
26            // Specify the path on the server to
27            // save the uploaded file to.
28            String savePath = Server.MapPath(IMG_PATH);
29
30            // Before attempting to perform operations
31            // on the file, verify that the FileUpload
32            // control contains a file.
33            if (imgUpload.HasFile)
34            {
35                // Get the name of the file to upload.
36                String fileName = imgUpload.FileName;
37
38                // Append the name of the file to upload to the path.
39                savePath += fileName;
40
41                // Call the SaveAs method to save the
42                // uploaded file to the specified path.
43                // This example does not perform all
44                // the necessary error checking.
45                // If a file with the same name
46                // already exists in the specified path,
47                // the uploaded file overwrites it.
48                imgUpload.SaveAs(savePath);
49
50                _xmlHelper.XmlPath = Server.MapPath("~/App_Data/ImagePaths.xml");
51                _xmlHelper.StoreImagePath(savePath);
52
53                SetPathInfo();
54            }
55        }
56        catch (Exception)
57        {
58            this.Page.ClientScript.RegisterStartupScript(this.GetType(), "", "alert('Image can not be uploaded, please check!'", true);
59        }
60    }
61
62
63    private void SetPathInfo()
64    {
65        string serverPath = "~/Images/Upload/";
66
67        XmlHelper xmlHelper = new XmlHelper();
68        xmlHelper.XmlPath = Server.MapPath("~/App_Data/ImagePaths.xml");
69        string imgPath = xmlHelper.GetImagepath();
70        string filename = GetFileName(imgPath);
71
72        serverPath += filename;
73
74        HtmlImage cropbox = (HtmlImage)Parent.FindControl("cropbox");
75        if (cropbox != null)
76            cropbox.Src = serverPath;
77        HtmlImage preview = (HtmlImage)Parent.FindControl("preview");
78        if (preview != null)
79            preview.Src = serverPath;
80
81        Context.Items["imgsrc"] = serverPath;
82    }
83
84    private string GetFileName(string fullname)
85    {
86        // Validation of string is not implemented temperarily
87        int index = fullname.LastIndexOf("\\");
88        string filename = fullname.Substring(index + 1);
89
90        return filename;
91    }
92}
93

XmlHelper类中用到的主要方法

1public void StoreImagePath(string img)
2    {
3        try
4        {
5            if (_xdoc == null)
6            {
7                _xdoc = XDocument.Load(XmlPath);
8            }
9
10            _xdoc.Root.Descendants().Remove();
11            _xdoc.Root.Add(new XElement("path", img));
12            _xdoc.Save(this.XmlPath);
13        }
14        catch
15        {
16            throw new Exception("Error occured in adding image path.");
17        }
18    }
19
20    public string GetImagepath()
21    {
22        string imagePath = string.Empty;
23
24        try
25        {
26            if (_xdoc == null)
27            {
28                _xdoc = XDocument.Load(XmlPath);
29            }
30
31            imagePath = _xdoc.Root.Descendants().First().Value.ToString();
32        }
33        catch
34        {
35            throw new Exception("Error occured in getting image path.");
36        }
37
38        return imagePath;
39    }

之后就是一个很重要的方法了。剪裁图片的方法，放在ImageHelper类中。

1public static string CropImage(string originamImgPath, string imgPath, int width, int height, int x, int y)
2    {
3        string filename = DateTime.Now.ToString("yyyyMMddHHmmss") + ".jpg";
4        byte[] CropImage = Crop(originamImgPath, width, height, x, y);
5        using (MemoryStream ms = new MemoryStream(CropImage, 0, CropImage.Length))
6        {
7            ms.Write(CropImage, 0, CropImage.Length);
8            using (System.Drawing.Image CroppedImage = System.Drawing.Image.FromStream(ms, true))
9            {
10                string SaveTo = imgPath + filename;
11                CroppedImage.Save(SaveTo, CroppedImage.RawFormat);
12            }
13        }
14
15        return filename;
16    }
17
18    private static byte[] Crop(string Img, int Width, int Height, int X, int Y)
19    {
20        try
21        {
22            using (Image OriginalImage = Image.FromFile(Img))
23            {
24                using (Bitmap bmp = new Bitmap(Width, Height, OriginalImage.PixelFormat))
25                {
26                    bmp.SetResolution(OriginalImage.HorizontalResolution, OriginalImage.VerticalResolution);
27                    using (Graphics Graphic = Graphics.FromImage(bmp))
28                    {
29                        Graphic.SmoothingMode = SmoothingMode.AntiAlias;
30                        Graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
31                        Graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
32                        Graphic.DrawImage(OriginalImage, new Rectangle(0, 0, Width, Height), X, Y, Width, Height, GraphicsUnit.Pixel);
33                        MemoryStream ms = new MemoryStream();
34                        bmp.Save(ms, OriginalImage.RawFormat);
35                        return ms.GetBuffer();
36                    }
37                }
38            }
39        }
40        catch (Exception Ex)
41        {
42            throw (Ex);
43        }
44    }

看下效果，demo阶段先不做优化了。
开始

显示上传的图片

图片剪裁

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2012-07-14 09:40
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