基于jquery和mini_magick的图片裁剪

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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。

Html代码

<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：

Js代码

<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

Ruby代码

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：