基于jquery和mini_magick的图片裁剪

jquery imgAeraSelect插件地址：http://odyniec.net/projects/imgareaselect/
原理很简单，就是将鼠标框住的区域两个定点坐标值传回服务器端，在服务器端用image magick处理。
由于rmagick存在内存泄露问题。这里选择了mini_magick。mini_magick是一个非常小的库，源代码不过300行。主要是通过调用系统命令行来处理图片。只要系统安装了image magick就可以。

view：主要是加四个隐藏域来传递裁剪区域。在form提交时候一起传递到服务器。

<input id="x1" type="hidden" value="0" name="x1"/>
         <input id="y1" type="hidden" value="0" name="y1"/>
         <input id="x2" type="hidden" value="150" name="x2"/>
         <input id="y2" type="hidden" value="150" name="y2"/>

<input id="x1" type="hidden" value="0" name="x1"/>
        <input id="y1" type="hidden" value="0" name="y1"/>
        <input id="x2" type="hidden" value="150" name="x2"/>
        <input id="y2" type="hidden" value="150" name="y2"/>

初始化裁剪框在待处理图片的中央和一些验证：

 <script type="text/javascript">
     $(document).ready(function(){
       var pos = initValue();


       $('#avatar').imgAreaSelect({aspectRatio: '1:1',
        x1: pos.x1,
        y1: pos.y1,
        x2: pos.x2,
        y2: pos.y2,
         handles: true,

         onSelectEnd: function (img, selection) {
           $('input[name=x1]').val(selection.x1);
           $('input[name=y1]').val(selection.y1);
           $('input[name=x2]').val(selection.x2);
           $('input[name=y2]').val(selection.y2);
        }
      });
    });

     function initValue(){
       var o    = new Object();
       var x    = $("#avatar").width();
       var y    = $("#avatar").height();
       var size = x >= y ? y : x;
      size     = size >= 100 ? 100 : size;
      o.x1 = (x - size) / 2;
      o.y1 = (y - size) / 2;
      o.x2 = o.x1 + size;
      o.y2 = o.y1 + size;
       return o;
    }



     function checkImage(){
       var image_name = $("#photo").val();
       var reg = /\.png|jpeg|jpg|bmp|gif$/i
       if (reg.test(image_name)){
         return true;
       }else if(image_name == "") {
         alert("没有选择图片！");
         return false;
       }else{
         alert("图片格式不正确！");
         return false;
      }
    }

  </script>

<script type="text/javascript">
    $(document).ready(function(){
      var pos = initValue();


      $('#avatar').imgAreaSelect({aspectRatio: '1:1',
        x1: pos.x1,
        y1: pos.y1,
        x2: pos.x2,
        y2: pos.y2,
        handles: true,
       
        onSelectEnd: function (img, selection) {
          $('input[name=x1]').val(selection.x1);
          $('input[name=y1]').val(selection.y1);
          $('input[name=x2]').val(selection.x2);
          $('input[name=y2]').val(selection.y2);
        }
      });
    });

    function initValue(){
      var o    = new Object();
      var x    = $("#avatar").width();
      var y    = $("#avatar").height();
      var size = x >= y ? y : x;
      size     = size >= 100 ? 100 : size;
      o.x1 = (x - size) / 2;
      o.y1 = (y - size) / 2;
      o.x2 = o.x1 + size;
      o.y2 = o.y1 + size;
      return o;
    }



    function checkImage(){
      var image_name = $("#photo").val();
      var reg = /\.png|jpeg|jpg|bmp|gif$/i
      if (reg.test(image_name)){
        return true;
      }else if(image_name == "") {
        alert("没有选择图片！");
        return false;
      }else{
        alert("图片格式不正确！");
        return false;
      }
    }
    
  </script>

后台处理，主要就是做以下几件事情：
1.把上传来的照片压缩到200x200
2.通过content-type判断图片是否合法。以防用户自己改扩展名。
3.把gif和png格式转换成jpg，不然在裁剪时候后出问题。
4.裁剪
5.把裁剪后图片缩放成几种比例

 def upload_avatar
     if request.post?
       avatar_200_200 = RAILS_ROOT + "/public/files/avatar/200_200/"
       photo_name     = "#{current_user.hash_id}.jpg"

       avatar_100_100 = RAILS_ROOT + "/public/files/avatar/100_100/"
       avatar_64_64   = RAILS_ROOT + "/public/files/avatar/64_64/"
       avatar_50_50   = RAILS_ROOT + "/public/files/avatar/50_50/"
       avatar_40_40   = RAILS_ROOT + "/public/files/avatar/40_40/"


       if params[:commit] == "上传照片"
         #TODO Validate Image Size!
         #TODO 增加白色背景，以防不规则图片!

         photo = params[:photo]

         raise "image type Error!" if photo.content_type !~ /^image\/.*?jpeg|jpg|png|bmp|gif$/i
         Dir.chdir avatar_200_200

        img  = MiniMagick::Image.from_blob(photo.read)
         img.format("jpg") if photo.content_type =~ /gif|png$/i

         img.resize "200x200"
        img.write photo_name

        redirect_to request.referer
       elsif params[:commit] == "保存设置"


         Dir.chdir avatar_200_200
         if File.exist?(photo_name)
           width = params[:x2].to_i - params[:x1].to_i
           height= params[:y2].to_i - params[:y1].to_i

          img = MiniMagick::Image.open(photo_name)

           img.crop "#{width}x#{height}+#{params[:x1]}+#{params[:y1]}"

           img.resize 100 and Dir.chdir avatar_100_100 and img.write photo_name
           img.resize 64  and Dir.chdir avatar_64_64   and img.write photo_name
           img.resize 50  and Dir.chdir avatar_50_50   and img.write photo_name
           img.resize 40  and Dir.chdir avatar_40_40   and img.write photo_name
         end
       end
     end
   end

def upload_avatar
    if request.post?
      avatar_200_200 = RAILS_ROOT + "/public/files/avatar/200_200/"
      photo_name     = "#{current_user.hash_id}.jpg"
      
      avatar_100_100 = RAILS_ROOT + "/public/files/avatar/100_100/"
      avatar_64_64   = RAILS_ROOT + "/public/files/avatar/64_64/"
      avatar_50_50   = RAILS_ROOT + "/public/files/avatar/50_50/"
      avatar_40_40   = RAILS_ROOT + "/public/files/avatar/40_40/"


      if params[:commit] == "上传照片"
        #TODO Validate Image Size!
        #TODO 增加白色背景，以防不规则图片!
        
        photo = params[:photo]
        
        raise "image type Error!" if photo.content_type !~ /^image\/.*?jpeg|jpg|png|bmp|gif$/i
        Dir.chdir avatar_200_200

        img  = MiniMagick::Image.from_blob(photo.read)
        img.format("jpg") if photo.content_type =~ /gif|png$/i
        
        img.resize "200x200"
        img.write photo_name

        redirect_to request.referer
      elsif params[:commit] == "保存设置"
        
        
        Dir.chdir avatar_200_200
        if File.exist?(photo_name)
          width = params[:x2].to_i - params[:x1].to_i
          height= params[:y2].to_i - params[:y1].to_i

          img = MiniMagick::Image.open(photo_name)
          
          img.crop "#{width}x#{height}+#{params[:x1]}+#{params[:y1]}"
        
          img.resize 100 and Dir.chdir avatar_100_100 and img.write photo_name
          img.resize 64  and Dir.chdir avatar_64_64   and img.write photo_name
          img.resize 50  and Dir.chdir avatar_50_50   and img.write photo_name
          img.resize 40  and Dir.chdir avatar_40_40   and img.write photo_name
        end
      end
    end
  end

效果预览：

 

来源:http://www.iteye.com/topic/541141