vue中图片转换为base64上传、预览、删除

<template>
    <div class="com-upload-img">
        <div class="img_group">
            <div class="img_box" v-if="allowAddImg">
                <input type="file" accept="image/*" multiple="multiple" @change="changeImg($event)">
                <div class="filter"></div>
            </div>
        <div class="img_box" v-for="(item,index) in imgArr" :key="index">
             <div class="img_show_box">
                <img :src="item" alt="">
                <i class="img_delete" @click="deleteImg(index)"></i>
                <!-- <i class="img_delete" @click="imgArr.splice(index,1)"></i> -->
            </div>
        </div>
        </div>
    </div>
</template>

<script>
export default {
    name:'ComUpLoad',
    data () {
        return {
            imgData:'',
            imgArr:[],
            imgSrc:'',
            allowAddImg:true,
        }
    },
methods: {
    changeImg: function(e) {
        var _this = this;
        var imgLimit = 1024;
        var files = e.target.files;
        var image = new Image();
        if(files.length>0){
            var dd = 0;
            var timer = setInterval(function(){
                if(files.item(dd).type != 'image/png'&&files.item(dd).type != 'image/jpeg'&&files.item(dd).type != 'image/gif'){
                    return false;
                }

            if(files.item(dd).size>imgLimit*102400){
                //to do sth
            }else{
                image.src = window.URL.createObjectURL(files.item(dd));
                image.onload = function(){
                // 默认按比例压缩
                var w = image.width,
                h = image.height,
                scale = w / h;
                w = 200;
                h = w / scale;
                // 默认图片质量为0.7，quality值越小，所绘制出的图像越模糊
                var quality = 0.7;
                //生成canvas
                var canvas = document.createElement('canvas');
                var ctx = canvas.getContext('2d');
                // 创建属性节点
                var anw = document.createAttribute("width");
                anw.nodeValue = w;
                var anh = document.createAttribute("height");
                anh.nodeValue = h;
                canvas.setAttributeNode(anw);
                canvas.setAttributeNode(anh);
                ctx.drawImage(image, 0, 0, w, h);
                var ext = image.src.substring(image.src.lastIndexOf(".")+1).toLowerCase();//图片格式
                var base64 = canvas.toDataURL("image/"+ext, quality );
                // 回调函数返回base64的值
                if(_this.imgArr.length<=4){
                    _this.imgArr.unshift('');
                    _this.imgArr.splice(0, 1, base64);//替换数组数据的方法，此处不能使用：this.imgArr[index] = url;
                if(_this.imgArr.length>=5){
                    _this.allowAddImg = false;
                }
            }
        }
    }

        if(dd<files.length-1){
            dd++;
        }else{
            clearInterval(timer);
        }
        },1000)
    }
},
deleteImg: function(index){
        this.imgArr.splice(index,1);
            if(this.imgArr.length<5){
            this.allowAddImg = true;
        }
    },
    },
}
</script>