v-model doesn’t support input type=”file”

In the onchange event you should pass the event object to a function and handle:

onFileChange(e) {
  var files = e.target.files || e.dataTransfer.files;
  if (!files.length)
    return;
  this.createImage(files[0]);
},

For more information refer https://codepen.io/Atinux/pen/qOvawK/