javaScript:压缩图片并上传

html代码:

<input id="file" type="file" name="filesName">

js代码:

    var fileElement = document.getElementById('file');

    fileElement.onchange = function(){
        var file = event.target.files[0];
        var upload = new uploadThumbnail({
            // name:"imgFileName", //缺省为 'imgs'
            // formName:"formName", //缺省为 'forms'
            // max:[maxWidth,maxHeight], //缺省为 [400*400]
            file:file,
            url:"./thumbnail.php",
            dataType:"json", //缺省为 'text'
            success:function( data ){
                console.info( data ); //打印接收的数据
                //this.newImgObj 为压缩后的图片对象
                document.body.append( this.newImgObj ) // 将图片加入页面
            }
        });
        upload.explain(); //在控制台打印说明 
    }

uploadThumbnail 对象:

(function(win,undefined){
    'use strict'
    var uploadThumbnail = function( obj ){
        this.newImgObj = null;
        this.init( obj );
        this.success = obj.success || function () {};
    }
    uploadThumbnail.prototype = {
        constructor:uploadThumbnail,
        // 入口函数
        init:function( obj ){
            this.compressPictures( obj );
        },
        // 压缩图片 并将画布传入上传函数
        compressPictures:function( obj ){
            obj = obj || {};
            obj.file = obj.file || "undefined";
            obj.url = obj.url || "undefined";
            var objThis = this;
            if( obj.file == "undefined" || obj.url == "undefined" ){
                console.info( "uploadThumbnail: 'file' and 'url' are required" );
                return false
            };
            // 压缩图片需要的一些元素和对象
            var reader = new FileReader(), newImg = new Image();
            // 缩放图片需要的canvas
            var canvas = document.createElement( 'canvas' );
            var context = canvas.getContext( '2d' );
            if ( obj.file.type.indexOf( "image" )==0 ) {
                reader.readAsDataURL( obj.file );
                // 文件base64化，以便获知图片原始尺寸
                reader.onload = function( e ) {
                    newImg.src = e.target.result;
                                    // base64地址图片加载完毕后
                    newImg.onload = function () {
                        // 图片原始尺寸
                        var originWidth = this.width;
                        var originHeight = this.height;
                        // 最大尺寸限制
                        var maxWidth, maxHeight;
                        try{
                            maxWidth = obj.max[0];
                            maxHeight = obj.max[1];
                        }catch( err ){
                            maxWidth = 400;
                            maxHeight = 400;
                        }
                        // 目标尺寸
                        var targetWidth = originWidth, targetHeight = originHeight;
                        // 图片尺寸超过400x400的限制
                        if ( originWidth > maxWidth || originHeight > maxHeight ) {
                            if ( originWidth / originHeight > maxWidth / maxHeight ) {
                                // 更宽，按照宽度限定尺寸
                                targetWidth = maxWidth;
                                targetHeight = Math.round( maxWidth * ( originHeight / originWidth ) );
                            } else {
                                targetHeight = maxHeight;
                                targetWidth = Math.round( maxHeight * ( originWidth / originHeight ) );
                            }
                        }
                            
                        // canvas对图片进行缩放
                        canvas.width = targetWidth;
                        canvas.height = targetHeight;
                        // 清除画布
                        context.clearRect( 0,0,targetWidth,targetHeight );
                        // 图片压缩
                        context.drawImage( newImg,0,0,targetWidth,targetHeight);

                        // 完成画布传入上传
                        objThis.upFile( obj,canvas );
                    };
                };
            }else{
                return false;
            }
        },
        upFile:function( obj,canvas ){
            var objThis = this;
            // canvas转为blob并上传
            canvas.toBlob(
                function (blob) {
                    // 生成图片
                    var newImg = document.createElement("img"),
                    url = URL.createObjectURL(blob);
                    newImg.onload = function() {
                        URL.revokeObjectURL(url);
                    };
                    obj.img == true 
                        ? newImg.src = canvas.toDataURL()
                        : newImg.src = url;
                    objThis.newImgObj = newImg;

                    // 创建表单数据
                    var formData = new FormData();
                    formData.append( obj.formName || 'forms',blob,obj.name || 'imgs' );

                    // 图片上传
                    var request  = new XMLHttpRequest();
                    // obj.async ? obj.async = true : obj.async = false;
                    request.open( "POST",obj.url,true );
                    request.send( formData );   
                    request.onreadystatechange = function() {
                        if ( request.readyState == 4 && request.status == 200 ) {
                            if( obj.dataType=="JSON" || obj.dataType=="json" ){
                                try{
                                    objThis.success( JSON.parse(request.responseText) )
                                }catch( err ){
                                    console.info( "banfeng reminds you: Error in converting received data to 'JSON' format" )
                                }
                            }else{
                                objThis.success( request.responseText )
                            }
                        }
                    }; 
                }, 
                obj.file.type || 'image/png',
            );
        },
        explain:function(){
            console.group( "This is uploadThumbnail" );
            console.log( 'new uploadThumbnail({' +
                            '
	name:imgFileName || "imgs",' +
                            '
	formName:formName || "forms",' +
                            '
	max:[maxWidth,maxHeight]  || [ 400*400 ],' +
                            '
	file:inputFile,' +
                            '
	url:URL,' +
                            '
	dataType:"json" || "text"' +
                            '
	success:functon(data){} Callback function on success' +
                            '
});' +
                            "
obj.newImgObj:Compressed image object" )
            console.groupEnd();
        }
    }
    win.uploadThumbnail = uploadThumbnail;
}(window));