I think you can do lossless cropping, but you have to restrict the cropping selection I believe due to how jpegs are encoded. I don’t know all the details. Chain of thought was “I’m just creating an image with a subset of existing data. Why do I need to re-encode?” -> “Because it’s lossy encoded, dummy. It was decoded so you could edit it. Now you have to re-encode it.” -> “Oh… apparently there are tricks that allow you to do it anyway due to the way the compression works.”
On the destructive save issue, setting both of those defaults to 1 works basically, so that’s cool 
As you indicated, the window opens untitled and so when you save, you have to select a format, folder, and file name when you save.
Some suggestions:
Instead of piggy backing on the existing untitled window use case:
- check for nonAcornDocumentURL on save
- pop up window warning of destructive save (can have this configurable via a default) with Cancel, Save, Save As
- If choosing Save As, default to the image’s original format, folder and file name. (A user would need to edit this, but would have the original filename populated if they just append edit strings to the original file name.)
Thanks for the info 