图片网络地址 转化base64

getBase64Image(img) {
    let canvas = document.getElementById('myCanvas')
    let ctx = canvas.getContext('2d')
    ctx.drawImage(img, 0, 0, 592, 333)
    let ext = img.src.substring(img.src.lastIndexOf('.') + 1).toLowerCase()
    let dataURL = canvas.toDataURL('image/' + ext)
    return dataURL
},

let image = new Image()

image.crossOrigin = ''
image.src = obj.img
image.onload = function () {
    let base64 = that.getBase64Image(image)
    console.log(base64)
    that.imgShow = base64
}