封一个图片转base64格式方法

async function imageToData64(Url) {  //传任意一图片地址
    return new Promise((resolve, reject) => {
      let image = new Image();
      image.src = itemUrl;
      image.crossOrigin = 'anonymous';
      image.onload = function () {
        let canvas = document.createElement('CANVAS');
        let context = canvas.getContext('2d');
        canvas.height = image.height;
        canvas.width = image.width;
        context.drawImage(image, 0, 0);
        try {
          let dataURL = canvas.toDataURL('image/jpeg');
          resolve(dataURL); //透出base64；
        } catch (e) {
          reject(e);
        }
        canvas = null;
      }
    });
  }