js 获取图片的宽高

获取图片的宽高

function get_image_dom_natural_wh(img_dom) {
  return new Promise((resolve) => {
    if (img_dom.naturalWidth && img_dom.naturalHeight) {
      return resolve({  img_dom.naturalWidth, height: img_dom.naturalHeight });
    } else {
      const img = new Image();

      img.src = img_dom.src;
      img.onload = () => {
        return resolve({  img.width, height: img.height });
      };
      img.onerror = () => {
        return resolve({  0, height: 0 });
      };
    }
  });
}

naturalWidth和naturalHeight是html5新增的属性，它们可以直接获取图片的原始宽高。而且这在Fixefox/Chrome/Safari/Opera/IE9里已经实现。