methods中新增方法

methods: {
            //异步执行
            imageUrlToBase64(img) {
                //一定要设置为let，不然图片不显示
                let image = new Image();

                //解决跨域问题
                image.setAttribute('crossOrigin', 'anonymous');

                let imageUrl = img;
                image.src = imageUrl;

                //image.onload为异步加载
                image.onload = () => {
                    var canvas = document.createElement("canvas");
                    canvas.width = image.width;
                    canvas.height = image.height;
                    var context = canvas.getContext('2d');
                    context.drawImage(image, 0, 0, image.width, image.height);

                    var quality = 0.6;
                    //这里的dataurl就是base64类型
                    //使用toDataUrl将图片转换成jpeg的格式,不要把图片压缩成png，因为压缩成png后base64的字符串可能比不转换前的长！
                    var dataURL = canvas.toDataURL("image/jpeg", quality);
                    console.log(dataURL)
                }
            },
}

调用：

this.imageUrlToBase64('https://s1.xmcdn.com/yx/ximalaya-web-static/last/dist/images/logo_a8388cb.png')