I want to create a new presentation and apply a powerpoint theme to it (any theme) so that when the powerpoint is opened and new slides are created, the rest of the slides follow the same theme.
Thanks for inquiring Aspose.Slides.
I have observed your requirements and like to share that you can load a template presentation with desired theme using Aspose.Slides. You can then add, update or delete slides using Aspose.Slides and save the presentation. Please visit this documentation section for your further kind reference in this regard.
Is it possible to just apply the theme directly to a presentation without having to load a template presentation? (Even if I need to switch over to .NET or a different type of aspose slides that’s fine)
I have observed your requirements and like to share that you can only clone the master slide from a presentation with desired template and then apply that on slides of your presentation. You can further work on your own presentation. You will be needed to use slide cloning feature for this. Please visit this documentation link for your further kind reference in this regard.