var img = new Image();   // 创建 img 元素
img.onload = function(){
  // 执行 drawImage 语句
}
img.src = 'myImage.png'; // 设置图片源地址

<template>
    <div>
        <canvas id="myCanvas" width="480" height="650"></canvas>
        <!-- <img src="../../assets/background.png" alt=""> -->
    </div>
</template>
<script>
export default {
    mounted() {
        this.initCancas();
    },
    methods: {
        initCancas() {
            console.log("初始化canvas");
            let canvas = document.getElementById('myCanvas');
            let context = canvas.getContext('2d');
            const bg = new Image();
            bg.src = "../../assets/background.png";
            context.drawImage(bg, 0,0);
            console.log('结束')
            bg.addEventListener("load", () => {
                setInterval(() => {
                    context.drawImage(this.bg, 0,0);
                },10)
            })
        },

    }
}
</script>
<style>
canvas {
      border: 1px solid red;
    }
</style>