HTML5移动开发图片压缩上传功能

var fileReader = new FileReader();fileReader.onload = function() {    var url = this.result;}//orfileReader.onload = function(e) {    var url = e.target.result;}

fileEle.onchange = function() {    if (!this.files.length) return;    //以下考虑的是单图情况    var _ua = window.navigator.userAgent;    var _simpleFile = this.files[0];    //判断是否为图片    if (!///(?:jpeg|png|gif)/i.test(_simpleFile.type)) return;    //插件exif.js获取ios图片的方向信息    var _orientation;    if(_ua.indexOf('iphone') > 0) {        EXIF.getData(_simpleFile,function(){            _orientation=EXIF.getTag(this,'Orientation');        });    }    //1.读取文件，通过FileReader，将图片文件转化为DataURL，即data:img/png;base64，开头的url，可以直接放在image.src中;    var _reader = new FileReader(),        _img = new Image(),        _url;    _reader.onload = function() {        _url = this.result;        _img.url = _url;        _img.onload = function () {            var _data = compress(_img);            uploadPhoto(_data, _orientation);        };    };    _reader.readAsDataURL(_simpleFile);};

/** * 计算图片的尺寸，根据尺寸压缩 * 1. iphone手机html5上传图片方向问题，借助exif.js * 2. 安卓UC浏览器不支持 new Blob()，使用BlobBuilder * @param  {Object} _img         图片 * @param  {Number} _orientation 照片信息 * @return {String}              压缩后base64格式的图片 */function compress(_img, _orientation) {    //2.计算符合目标尺寸宽高值，若上传图片的宽高都大于目标图，对目标图等比压缩；如果有一边小于，对上传图片等比放大。    var _goalWidth = 750,                  //目标宽度        _goalHeight = 750,                 //目标高度        _imgWidth = _img.naturalWidth,     //图片宽度        _imgHeight = _img.naturalHeight,   //图片高度        _tempWidth = _imgWidth,            //放大或缩小后的临时宽度        _tempHeight = _imgHeight,          //放大或缩小后的临时宽度        _r = 0;                            //压缩比    if(_imgWidth === _goalWidth && _imgHeight === _goalHeight) {    } else if(_imgWidth > _goalWidth && _imgHeight > _goalHeight) {//宽高都大于目标图，需等比压缩        _r = _imgWidth / _goalWidth;        if(_imgHeight / _goalHeight < _r) {            _r = _imgHeight / _goalHeight;        }        _tempWidth = Math.ceil(_imgWidth / _r);        _tempHeight = Math.ceil(_imgHeight / _r);    } else {        if(_imgWidth < _goalWidth && _imgHeight < _goalHeight) {//宽高都小于            _r = _goalWidth / _imgWidth;            if(_goalHeight / _imgHeight < _r) {                _r = _goalHeight / _imgHeight;            }        } else {            if(_imgWidth < _goalWidth) {         //宽小于                _r = _goalWidth / _imgWidth;            } else{                              //高小于                _r = _goalHeight / _imgHeight;            }        }        _tempWidth = Math.ceil(_imgWidth * _r);        _tempHeight = Math.ceil(_imgHeight * _r);    }    //3.利用canvas对图片进行裁剪，等比放大或缩小后进行居中裁剪    var _canvas = e._$get('canvas-clip');    if(!_canvas.getContext) return;    var _context = _canvas.getContext('2d');    _canvas.width = _tempWidth;    _canvas.height = _tempHeight;    var _degree;    //ios bug，iphone手机上可能会遇到图片方向错误问题    switch(_orientation){       //iphone横屏拍摄，此时home键在左侧        case 3:            _degree=180;            _tempWidth=-_imgWidth;            _tempHeight=-_imgHeight;            break;        //iphone竖屏拍摄，此时home键在下方(正常拿手机的方向)        case 6:            _canvas.width=_imgHeight;            _canvas.height=_imgWidth;             _degree=90;            _tempWidth=_imgWidth;            _tempHeight=-_imgHeight;            break;        //iphone竖屏拍摄，此时home键在上方        case 8:            _canvas.width=_imgHeight;            _canvas.height=_imgWidth;             _degree=270;            _tempWidth=-_imgWidth;            _tempHeight=_imgHeight;            break;    }    if(window.navigator.userAgent.indexOf('iphone') > 0 && !!_degree) {        _context.rotate(_degree*Math.PI/180);        _context.drawImage(_img, 0, 0, _tempWidth, _tempHeight);     } else {        _context.drawImage(_img, 0, 0, _tempWidth, _tempHeight);    }    //toDataURL方法，可以获取格式为"data:image/png;base64,***"的base64图片信息；    var _data = _canvas.toDataURL('image/jpeg');    return _data;}

/** * 上传图片到NOS * @param  {Object} _blog Blob格式的图片 * @return {Void} */function uploadPhoto(_data) {    //4.获取canvas中的图片信息    //window.atob方法将其中的base64格式的图片转换成二进制字符串；若将转换后的值直接赋值给Blob会报错，需Uint8Array转换：最后创建Blob对象；    _data = _data.split(',')[1];    _data = window.atob(_data);    //如果不用ArrayBuffer,发送给服务器的图片格式是[object Uint8Array],上传失败...    var _buffer = new ArrayBuffer(_data.length);    var _ubuffer = new Uint8Array(_buffer);    for (var i = 0; i < _data.length; i++) {        _ubuffer[i] = _data.charCodeAt(i);    }    // 安卓 UC浏览器不支持 new Blob()，使用BlobBuilder    var _blob;    try {        _blob = new Blob([_buffer], {type:'image/jpeg'});    } catch(ee) {        window.BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder || window.MSBlobBuilder;        if (ee.name == 'TypeError' && window.BlobBuilder) {            var _bb = new BlobBuilder();            _bb.append(_buffer);            _blob = _bb.getBlob('image/jpeg');        }    }    var _suffix = 'jpg';    if(_blob.type === 'image/jpeg') {        _suffix = 'jpg';    }    //获取NOStoken    this.__cache._$requestDWRByGet({url: 'ImageBean.genTokens',param: [_suffix,'','','','1'],onload: function(_tokens) {        _tokens = _tokens || [];        var _token = _tokens[0];        if(!_token || !_token.objectName || !_token.uploadToken){            alert('token获取失败！');            return false;        }        //上传图片到NOS        var _objectName = _token.objectName,            _uploadToken = _token.uploadToken,            _bucketName = _token.bucketName;        var _formData = new FormData();        _formData.append('Object', _objectName);        _formData.append('x-nos-token', _uploadToken);        _formData.append('file',_blob);        var _xhr;        if (window.XMLHttpRequest) {            _xhr = new window.XMLHttpRequest();        } else if (window.ActiveXObject) {            _xhr = new ActiveXObject("Microsoft.XMLHTTP");        }        _xhr.onreadystatechange = function() {            if(_xhr.readyState === 4) {                if((_xhr.status >= 200 && _xhr.status < 300) || _xhr.status === 304) {                    var _imgurl = "http://nos.netease.com/" + _bucketName + "/" + _objectName + "?imageView";                    var _newUrl = mb.x._$imgResize(_imgurl, 750, 750, 1, true);                    window.location.href = 'http://www.lofter.com/act/taxiu?op=effect&originImgUrl=' + _newUrl;                }            }        };        _xhr.open('POST', 'http://nos.netease.com/' + _bucketName, true);        _xhr.send(_formData);    }});}