SOURCE

const image = new Image();

image.onload = () => {
    console.log(image.width);
  // 构建canvas节点
  const canvas = document.createElement('canvas');
  canvas.width = image.width;
  canvas.height = image.height;
  const context = canvas.getContext('2d');
  context.drawImage(image, 0, 0, image.width, image.height);
  // 转换
  const imgBase64 = canvas.toDataURL();
  console.log(imgBase64);
};

image.src = 'https://cdns.jsrun.net/css/img/logo@2x.png';