(Running GIMP 2.8.10 on Linux Mint 13. Camera is a Kodak EasyShare C713 that I got for free as a workplace bonus a few years ago.)
I have noticed that Gwenview (the default KDE image viewer) uses a scaling process which produces better results than GIMP in many situations. The attached file shows a cropped comparison between the results of resizing an image in GIMP (left) and Gwenview (right). The Sinc/Lanczos3 routine was used in GIMP; Cubic and Linear were also tried but did not work better. The difference is most obvious in the window screen. Similar effects occur with other objects prone to aliasing issues, for example architectural subjects with lots of straight lines (window grids, tiled roofs etc.). What I've ended up doing most of the time is doing everything in GIMP except the scaling, then exporting the image, opening it with Gwenview, scaling it there, and saving it again, which is a bit cumbersome.
What process is Gwenview using to scale images, and would it be possible for A) GIMP to add it to the available Image/Scale Image options, or B) some wizard here to write a plugin that would do the same thing?
Or, if I am missing some setting in the GIMP preferences that would improve this, please give me the heads-up.