title: How to write or modify EXIF data for an existing image on the filesystem, without loading the image?
body: <p>I've asked similar questions before, but have not received a definitive answer. Seems that there must be a way to simply add/modify metadata to an image without loading the image into memory, without having to deal with directly reading bits.</p>
  
  <p>Seems like ways exist when using <code>CMSampleBufferRef</code>s, but I need to be able to do this with a regular image already saved to disk.<br>
  For instance, given a very large <code>png</code> at <code>/Documents/photo.png</code>, I want to modify its exif metadata without having to load that image.</p>