Asp.Net平台下的图片在线裁剪功能的实现

最近项目中有个图片在线裁剪功能,本人查找资料,方法如下:前台展现用jquery.Jcrop实现,后台使用 System.Drawing.Image类来进行裁剪.

1.前台展现实现

网上找到这个jquery.Jcrop,稍看了下,发现它提供的效果完全能满足项目需求.

官方网址:http://deepliquid.com/content/Jcrop.html,感兴趣的朋友可去看看.

页面先引用相关样式和脚本:

 <link href="Styles/jquery.Jcrop.css" rel="stylesheet" type="text/css" />

    <script src="Scripts/jquery-1.4.1.js" type="text/javascript"></script>

    <script src="Scripts/jquery.Jcrop.js" type="text/javascript"></script>

页面body部分代码:

 <asp:Label ID="Label1" Text="原始图片" runat="server"></asp:Label><br />

        <asp:Image ID="target" runat="server" />

        <br />

        <asp:Label ID="Label2" runat="server" Text="最终显示效果"></asp:Label>

        <div id="preImg" style="width: 150px; height: 80px; overflow: hidden;">

            <asp:Image ID="preview" alt="Preview" runat="server" />

        </div>

其中ID为preImg的Style的width和height的值是裁剪图片的尺寸,而且要定义这个DIV的overflow:hidden.能够及时看到图片的裁剪效果的关键CSS属性就是它了.

接下来讲讲jquery.Jcrop.js的基本用法,及相关javascript的实现.

首先定义一些临时变量,来保存相关参数

         var jcrop_api, boundx, boundy;

然后给图片的DOM元素绑定Jcrop功能,相关的方法属性看英文就能明白其中的意思.

$('#target').Jcrop({

                   onChange: updatePreview,

                   onSelect: updatePreview,

                   onRelease: clearCoords,

                   aspectRatio: 150 / 80,

                   minSize: _minarray,

                   setSelect: _array

               }, function () {          

                   var bounds = this.getBounds();

                   boundx = bounds[0];

                   boundy = bounds[1];

                    jcrop_api = this;

               });

//此方法是用来及时展现图片裁剪效果

               function updatePreview(c) {

                   if (parseInt(c.w) > 0) {

                       var rx = 150 / c.w;

                       var ry = 80 / c.h;

                       var _width;

                       var _height;

                       if (Math.round(rx * boundx) > $targetImg.width()) {

                           _width = $targetImg.width();

                       }

                       else {

                           _width = Math.round(rx * boundx);

                       }

                       if (Math.round(ry * boundy) > $targetImg.height()) {

                           _height = $targetImg.height();

                       }

                       else {

                           _height = Math.round(ry * boundy);

                       }

                       $('#preview').css({

                           width: _width + 'px',

                           height: _height + 'px',

                           marginLeft: '-' + Math.round(rx * c.x) + 'px',

                           marginTop: '-' + Math.round(ry * c.y) + 'px'

                       });

                   }

                   $('#x1').val(c.x);

                   $('#y1').val(c.y);



                   $('#Iwidth').val(c.w);

                   $('#Iheight').val(c.h);

               };

另一部分前台代码: 

<form id="Form1" runat="server">

        <asp:HiddenField ID="HdnNewImgPath" runat="server" />

        <asp:HiddenField ID="x1" runat="server" />

        <asp:HiddenField ID="y1" runat="server" />

        <asp:HiddenField ID="Iwidth" runat="server" />

        <asp:HiddenField ID="Iheight" runat="server" />

        <br />

        <asp:Button ID="SaveImg" runat="server" Text="裁剪并保存图片" OnClick="saveImg" OnClientClick="return CheckIMG()" />

        </form>

 后台代码的实现:

首先引用相关命名空间

using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Design;

保存按钮的方法,从页面取到相关参数,然后调用裁剪方法.

protected void saveImg(object sender, EventArgs e)

       {

           if (IsPostBack)

           {

               string tempurl = Path.Combine(ConfigAccess.UploadImagePath, _url);

               int startX = int.Parse(x1.Value);

               int startY = int.Parse(y1.Value);

               int width = int.Parse(Iwidth.Value);

               int height = int.Parse(Iheight.Value);

               ImgReduceCutOut(startX, startY, width, height, tempurl, tempurl);

               this.target.Visible = false;

               this.Label1.Visible = false;

               this.SaveImg.Enabled = false;

           }

       }

接下是最重要的裁剪方法:

  <SPAN style="COLOR: blue">public void </SPAN>ImgReduceCutOut(<SPAN style="COLOR: blue">int </SPAN>startX, <SPAN style="COLOR: blue">int </SPAN>startY, <SPAN style="COLOR: blue">int </SPAN>int_Width, <SPAN style="COLOR: blue">int </SPAN>int_Height, <SPAN style="COLOR: blue">string </SPAN>input_ImgUrl, <SPAN style="COLOR: blue">string </SPAN>out_ImgUrl)
       {
           <SPAN style="COLOR: green">// 上传标准图大小
           </SPAN><SPAN style="COLOR: blue">int </SPAN>int_Standard_Width = 150;
           <SPAN style="COLOR: blue">int </SPAN>int_Standard_Height = 80;

<SPAN style="COLOR: green">//其实在图片裁剪过程中还可以传更多的参数,如把原始图片缩小了再进行裁剪.本实例中是</SPAN><SPAN style="COLOR: #008000" color="#008000">裁剪后,再裁剪后的图片缩小成150X80</SPAN>

              //通过连接创建Image对象

           System.Drawing.Image oldimage = System.Drawing.Image.FromFile(input_ImgUrl);

           oldimage.Save(Server.MapPath("temp.jpg"));//把原图Copy一份出来,然后在temp.jpg上进行裁剪,最后把裁剪后的图片覆盖原图

           oldimage.Dispose();//一定要释放临时图片,要不之后的在此图上的操作会报错,原因冲突

           Bitmap bm = new Bitmap(Server.MapPath("temp.jpg"));

           //处理JPG质量的函数

           ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();

           ImageCodecInfo ici = null;

           foreach (ImageCodecInfo codec in codecs)

           {

               if (codec.MimeType == "image/jpeg")

               {

                   ici = codec;

                   break;

               }

           }

           EncoderParameters ep = new EncoderParameters();

           ep.Param[0] = new EncoderParameter(Encoder.Quality, (long)level);



           // 裁剪图片

           Rectangle cloneRect = new Rectangle(startX, startY, int_Width, int_Height);

           PixelFormat format = bm.PixelFormat;

           Bitmap cloneBitmap = bm.Clone(cloneRect, format);

           if (int_Width > int_Standard_Width)

           {

               //缩小图片

               System.Drawing.Image cutImg = cloneBitmap.GetThumbnailImage(int_Standard_Width, int_Standard_Height, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);

               cutImg.Save(out_ImgUrl, ici, ep);

               cutImg.Dispose();

           }

           else

           {

               //保存图片

               cloneBitmap.Save(out_ImgUrl, ici, ep);

           }

           cloneBitmap.Dispose();

           bm.Dispose();

       }



        public bool ThumbnailCallback()

        {

            return false;

        }

至此,图片在线裁剪功能完成

主要页面源码:source

绿