H5单文件压缩插件

单文件压缩上传

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

构造函数

function UpFileImg(options){
    var options =  options || {
        el:'',
        compressSize:640,
        datatype:'base64',
        success:function(val){}
    };
    var that = this;

    // 读取文件
    this.setFilesReader = function(file){
        var reader = new window.FileReader();
        var fileSize = Math.round(file.size/1024/1024);
        var that = this;
        reader.readAsDataURL(file);
        reader.onload = function(e) {
            that.compress(this.result,fileSize);
        };
    };
    // 压缩文件
    this.compress = function(res, fileSize){
        var img = new Image();
        var maxW = options.compressSize; //压缩后大小
        var that = this;
        img.src = res;
        img.onload = function () {
            var cvs = document.createElement('canvas'), ctx = cvs.getContext('2d');

            if(img.width > maxW) {
                img.height *= maxW / img.width;
                img.width = maxW;
            }

            cvs.width = img.width;
            cvs.height = img.height;

            ctx.clearRect(0, 0, cvs.width, cvs.height);
            ctx.drawImage(img, 0, 0, img.width, img.height);

            // 设置压缩比
            var compressRate = that.getCompressRate(1,fileSize);

            // 压缩
            var dataUrl = cvs.toDataURL('image/jpeg', compressRate);
            if(options.datatype === 'blob'){
                var dataUrl =  that.dataURItoBlob(dataUrl);
            }
            // 成功后回调
            that.compressCallblak(options.success,dataUrl);
        };
    };

    // 压缩后回调函数
    this.compressCallblak = function(fun,val){
        fun(val);
    };

    // 计算压缩比
    this.getCompressRate = function(allowMaxSize,fileSize){
        var compressRate = 1;
        
        if(fileSize/allowMaxSize > 4){
           compressRate = 0.5;
        } else if(fileSize/allowMaxSize >3){
           compressRate = 0.6;
        } else if(fileSize/allowMaxSize >2){
           compressRate = 0.7;
        } else if(fileSize > allowMaxSize){
           compressRate = 0.8;
        } else{
           compressRate = 0.9;
        }
        return compressRate;
    };
    
    //base64转blob
    this.dataURItoBlob = function(base64Data){
        var byteString;
        if (base64Data.split(',')[0].indexOf('base64') >= 0){
            byteString = atob(base64Data.split(',')[1]);
        }
        else{
            byteString = unescape(base64Data.split(',')[1]);
        }
        var mimeString = base64Data.split(',')[0].split(':')[1].split(';')[0];
        var ia = new Uint8Array(byteString.length);
        for (var i = 0; i < byteString.length; i++) {
            ia[i] = byteString.charCodeAt(i);
        }
        return new Blob([ia], {type:mimeString});
    }

    document.getElementById(options.el).onchange = function (){
        var f = this.files[0];
        that.setFilesReader(f);
    };
};

示例：（转为blob对象后使用ajax上传）

var fileImg = new UpFileImg({
    el:'file',     //绑定id
    compressSize:700,     //默认640
    datatype:'blob',    //默认转换为base64
    success:function(data,name){
        // 回调
        console.log(data);
        console.log(name);
        var fd = new FormData();
        
        // file_key为上传文件后台对应的key也就相当于input的name，
        // data为bolo对象，
        // name为上传文件的名称
        fd.append("file_key", data, name);
        $.ajax({
            url: '上传地址',
            type: 'POST',
            data: fd,
            processData: false, // 必须
             contentType: false, // 必须
            dataType: 'json',
            success:function(data){
                console.log(data);    
            }
        });
    }
});

名称	默认值	是否必传	描述
el	无	是	对应input的ID
compressSize	640	否	压缩后最大宽度
datatype	base64	否	回调函数返回值类型，默认返回base64，可以设置为blob，配合ajax进行上传
success	无	是	回调函数返回文件名称，与压缩后文件（base64或者blob）