I am know the funktions in Qimage, and i am sugesting it to be the best to do the job, that means to maximise the use off the foto papers, to fit nice in the frame, and still have the overall porporsions off the poster picture when hanging on the wall, if Qimage could have a user interface a bit like PosteRazor, it would just be amasing...
please have a look at it here, if you would like to test my wish for qimage..
https://posterazor.sourceforge.io/