gistfile1.js

let extractBitmapSize = (bitmap, callback) => {
  let imageElement = new Image();

  imageElement.onload = () => {
    callback(imageElement.naturalWidth, imageElement.naturalHeight);
  };

  imageElement.src = bitmap;
};

document.body.addEventListener('drop', (event) => {
  event.stopPropagation();
  event.preventDefault();

  let files = event.dataTransfer.files;

  for (let file of files) {
    if (file.type === 'image/png') {
      let reader = new FileReader();
      reader.readAsDataURL(file);

      reader.addEventListener('load', (event) => {
        let bitmap = event.target.result;

        extractBitmapSize(bitmap, (width, height) => {
          let image = SVG`<image></image>`;
          image.setAttribute('width', width);
          image.setAttribute('height', height);
          image.setAttributeNS(xlinkNS, 'xlink:href', `${bitmap}`);
          image.appendTo(this.graphics);
        });
      });
    }

  }
});