javascirpt    (function($){
            $.fn.extend({
                aiiUpload:function(obj)
                {
                    if(typeof obj !="object")
                    {
                        alert('参数错误');
                        return;
                    }
                    var imageWidth,imageHeight;
                    var base64;
                    var file_num=0;
                    var fileInput=$(this);
                    var fileInputId=fileInput.attr('id');
                    createDoc('#'+fileInputId,obj.method,obj.action);
                    $('#aii_file').change(function(){
                        if(test(this.value)==false)
                        {
                            alert('格式错误');
                            return;
                        }
                        var objUrl = getObjectURL(this.files[0]);
                        if (objUrl) 
                        {
                            imgBefore(objUrl,file_num);
                            render(objUrl,obj.max_h,obj.max_w,file_num);
                            file_num++;
                        }
                    });
                }
            });
            function createDoc(objID,form_method,form_action)
            {
                var element=$(objID);
                element.append('<ul class="viewList"></ul>').append('<div class="fileBox"><input type="file"  id="aii_file" /><div class="file_bg"></div></div>').append('<form id="aii_upload_form" method="'+form_method+'" action="'+form_action+'"></form>').append('<canvas id="canvas"></canvas>');
            }
            function test(value)
            {
                var regexp=new RegExp("(.JPEG|.jpeg|.JPG|.jpg|.GIF|.gif|.BMP|.bmp|.PNG|.png)$",'g');
                return regexp.test(value);
            }
            function render(src,MaximgW,MaximgH,idnum)
            {
                var image=new Image();
                image.onload=function()
                {
                    var canvas=document.getElementById('canvas');
                    if(image.width>image.height)
                    {
                        imageWidth=MaximgW;
                        imageHeight=MaximgH*(image.height/image.width);
                    }
                    else if(image.width<image.height)
                    {
                        imageHeight=MaximgH;
                        imageWidth=MaximgW*(image.width/image.height);
                    }
                    else
                    {
                        imageWidth=MaximgW;
                        imageHeight=MaximgH;
                    }
                    canvas.width=imageWidth;
                    canvas.height=imageHeight;
                    var con=canvas.getContext('2d');
                    con.clearRect(0,0,canvas.width,canvas.height);
                    con.drawImage(image,0,0,imageWidth,imageHeight);
                    base64=canvas.toDataURL('image/jpeg',0.5).substr(22);
                    add_doc(base64,idnum);
                }
                image.src=src;
            };
            //建立一個可存取到該file的url
            function getObjectURL(file) {
                var url = null ; 
                if (window.createObjectURL!=undefined) { // basic
                    url = window.createObjectURL(file) ;
                } else if (window.URL!=undefined) { // mozilla(firefox)
                    url = window.URL.createObjectURL(file) ;
                } else if (window.webkitURL!=undefined) { // webkit or chrome
                    url = window.webkitURL.createObjectURL(file) ;
                }
                return url ; 
            }
            //预览
            function imgBefore(objUrl,idnum) 
            {
                var li='<li class="view"><img src="'+objUrl+'" id="aiiImg_'+idnum+'" idnum="'+idnum+'" /><div class="close" onclick="img_remove(this);"></div></li>'
                $('.viewList').append(li);
                var img=$('#aiiImg_'+idnum);
                //预览图片居中 填满 代码
                console.log('asdfasdfasdf');

                img.load(function(){
                    var imgw=img.width(),
                        imgh=img.height();
                        console.log(imgw);
                        console.log(imgh);
                    if(imgw>imgh)
                    {
                        img.css('height','100%');
                        img.css('width','auto');
                        img.css('marginLeft',-(img.width()-img.height())/2+'px');
                    }
                    else if(imgw<imgh)
                    {
                        img.css('width','100%');
                        img.css('height','auto');
                        img.css('marginTop',-(img.height()-img.width())/2+'px');
                    }
                });
            }

            function add_doc (base,idnum)
            {
                $('#aii_upload_form').append('<input type="hidden" name="img[]" id="f_'+idnum+'" value="'+base+'"/>');
            }
        })(jQuery);
        function img_remove(element)
        {
            var num=$(element).prev().attr('idnum');
            $(element).parent().remove();
            $('#f_'+num).remove();
            console.log('asdf');
        }

html
<section class="section">  
    <div id="box"></div> 
    <p style="color:red;">*样式修改请参考aiiUpload.css</p>
</section>  

javascript<script type="text/javascript">  
    $('#box').aiiUpload({  
        method:'POST',  
        action:'form.php',  
        max_h:300,  
        max_w:300,  
        subText:'上传图片',  
        fileText:'选择图片'  
    });  
</script>