Just grab attachment IDs instead of objects.
Clean up deprecated functions.
Code cleanup. A few bug fixes. Loads of inline docs.
$args should be $this->args.  Merge a that bit of code too.
$image should be $this->image_args.
$this->arg should be $this->args.
Use $args instead of $this->args.
Corrections in get_scan_image().
Don't overwrite $this->args.  New $caption_args variable fixes that.