I have observed the presentation file shared by you. Can you please share the fonts used in your presentation. If you are using Open Type fonts then I regret to share that at the moment the support for Open Type fonts is currently unavailable in Aspose.Slides.
thank you for your quick response. We do use true type fonts, but there are also other font type within the directory. As I wrote, the solution works on Windows Machine, but does not work on AIX with the same set of fonts. I will clean the directory, so that only true type fonts will be available.
I my font directory is empty, I do not get the NullPointerException at loadExternalFonts. If I put one TrueType Fonts, I still get the NullPointerException. I share with you the Font File (see Attachment), can you reproduce the problem on AIX?
I would suggest you to please try loading the custom font from location by removing the True Type fonts from target directory. If there is still an issue with other fonts then please share the fonts with us and I will try to reproduce the issue on my end to help you further.
I have created an issue with ID SLIDESJAVA-33568 in our issue tracking system to provide FontLoader support in Aspose.Slides for Java. Actually, this new version has been auto ported from Aspose.Slides for .NET so this FontLoader has been missed in this release.