In PowerPoint, you can just select everything, then right-click -> save as image, and it saves whatever you have selected rather than the whole slide. There doesn’t seem to be a way to do that in Impress, but I realised you could copy-paste into Gimp and that would copy the objects as an image, so I’ve been making memes that way.
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The issue is that the slide size isn’t going to match with the meme size and there’s no way to predict it. … unless there’s a workaround that I’m not aware of. I’d need it to ignore the slide size and only include the images. The only way I found I could do that in libre office is to highlight and copy/paste.
In PowerPoint, you just highlight all images->right click->save as picture and that works just fine.
I guess I’ll just have to work the courage to make feature requests, or better yet, understand open source code to make improvements.