image widthFix 动态修改width，height没改变

问题：image widthFix 动态修改width，height没改变

<template>  
    <view class="content">  
        <image :style="'width:'+width+'px;'" mode="widthFix" class="logo" src="/static/logo.png"></image>  
        <view class="text-area">  
            <text class="title">{{title}}</text>  
        </view>  
    </view>  
</template>  

<script>  
    export default {  
        data() {  
            return {  
                title: 'Hello',  
                width:100,  
            }  
        },  
        onLoad() {  
            var that = this;  
            setTimeout(()=>{  
                that.width = 200;  
                that.$forceUpdate();  
            },3000)  
        },  
        methods: {  

        }  
    }  
</script>  

<style>  
    image{will-change: transform}  
    .content {  
        display: flex;  
        flex-direction: column;  
        align-items: center;  
        justify-content: center;  
    }  

    .logo {  
        height: 200rpx;  
        width: 200rpx;  
        margin-top: 200rpx;  
        margin-left: auto;  
        margin-right: auto;  
        margin-bottom: 50rpx;  
    }  

    .text-area {  
        display: flex;  
        justify-content: center;  
    }  

    .title {  
        font-size: 36rpx;  
        color: #8f8f94;  
    }  
</style>