Why it's not possible to save a PNG image from Preview when a mask is added?

Solution 1:

This is a bug with Preview.

Preview -[CIImage initWithCGImage:options:] failed because the CGImage is nil.
Preview Error: CGImageForSavingWithFlattenedEXIF:depth: failed
Preview finalize:2403: image destination must have at least one image

You can report bugs to Apple at https://bugreport.apple.com.

Solution 2:

I am having exactly same issue on my end.

Highlight is a function I need to use everyday. Hope Apple fix this as soon as possible.

Current stupid workaround is

1. Use preview to set highlight area.
2. Use command+shift+4 to take screenshot on preview.

😩

Solution 3:

Export to PNG before making changes. Open the PNG file and edit it. Use Instant Alpha to delete background. Finalize and save. For other changes I suggest exporting it to JPEG or other

Solution 4:

Alternative solution to screenshot...

1. Cmd + Shift + S to duplicate
2. Cmd + S to save
3. Save as PDF
4. edit
5. Export as PNG

Not really sure it's a better solution, just another workaround.

Follow up to this... It appears that Preview in Mojave is working. I was on the previous version when I posted this answer. I'm still not on Catalina yet, but it's working for me in Mojave.