If it's a simple combo of photos... Should be able to do it right in Google photos under the utilities tab.
Thanks for the hint. I haven't used Google Photos in a while and its features sound like what I want: https://support.google.com/photos/answer/12637115?hl=en&co=GENIE.Platform%3DAndroid
However, it is not an open source app.
Boo hoo. Get off your high horse. It works.
The best workaround I found so far is to add a new tag to some images in my gallery app (Aves Libre), then filter for that tag and take a screenshot of it. It is neither possible to order the images nor to scale some of them. But it is definitely better than nothing ;)
F-Droid
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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