04-18-2019, 01:36 PM
If I understand right, you need to add an alpha channel to these images. Have you tried right-clicking your base image and adding an alpha channel? JPG images did not load with an alpha channel until 2.10.10, which released a few days ago. Now you can set GIMP to automatically add an alpha channel to jpg images. The switch is in Preferences>Image Import & Export >Import Policies.