Never a good idea to upscale more than a little, because of interpolations, graphics lose definition.
A good idea is to give the size in pixels of your images
What do you call HD? maybe 1280 x 720 pixels? Full HD is 1920 x 1080 pix and 4k can be 3840 x 2160 pix.
All of those are 16:9 aspect ratio. If your work is already 4:3 ratio then you have two options. Add a 'pillar' to each side to pad out to widescreen or crop your 4:3 image to 16:9 (and losing top/bottom) before upscaling.
What is the best course for you?
Back to the beginning, does not matter much if you use Gimp / PS / or some other application, scaling up loses quality. Depends how much you upscale.
Edit: Just wondering if you need to use an anamorphic format for your application
DVD video regardless of 4:3 or 16:9 aspect ratio has a 'frame size' size 720 x 540 (PAL) pixels. For wide screen 16:9 the pixels are not square, they have more height than width. When played the video player stretches the pixel to 'square' and the picure becomes widescreen.
Gimp can adjust the x and y resolutions to different values for an anamorphic picture.
Then where do you expect the work to be displayed? For a TV some small images display quite well, I have some 1000 x 600 video that plays perfectly well on a 1920 x 1080 TV. Even regular DVD format is not too bad.
A good idea is to give the size in pixels of your images
What do you call HD? maybe 1280 x 720 pixels? Full HD is 1920 x 1080 pix and 4k can be 3840 x 2160 pix.
All of those are 16:9 aspect ratio. If your work is already 4:3 ratio then you have two options. Add a 'pillar' to each side to pad out to widescreen or crop your 4:3 image to 16:9 (and losing top/bottom) before upscaling.
What is the best course for you?
Quote:... make sure my image quality isn't trashed by the resizing..
Back to the beginning, does not matter much if you use Gimp / PS / or some other application, scaling up loses quality. Depends how much you upscale.
Edit: Just wondering if you need to use an anamorphic format for your application
DVD video regardless of 4:3 or 16:9 aspect ratio has a 'frame size' size 720 x 540 (PAL) pixels. For wide screen 16:9 the pixels are not square, they have more height than width. When played the video player stretches the pixel to 'square' and the picure becomes widescreen.
Gimp can adjust the x and y resolutions to different values for an anamorphic picture.
Then where do you expect the work to be displayed? For a TV some small images display quite well, I have some 1000 x 600 video that plays perfectly well on a 1920 x 1080 TV. Even regular DVD format is not too bad.