Dear GIMP developers,

I want to implement a bicubic scaling routine for Krita, a painting and image processing application for KDE. As a proof of concept I coded a bilinear scaling routine this morning which does work quite well if the scale factor is not too small or too large (e.g. in the range 0.5 - 2.0). The algorithm is from "Numerical Recipes". This book also has a chapter about bicubic interpolation and I think that it would not be too hard to improve my original very simple algorithm to use bicubic interpolation.

As a long-time GIMP user, I know that the GIMP scaling algorithms are really good and I would like to have a look on the algorithms and maybe use them for scaling in Krita. I looked at the GIMP source code but I could not find the relevant parts of the code. Could you please tell me in what files the relevant parts of the code are?

I know you would prefer people to work on GIMP and I think GIMP is really a great application and I love to use it. But there are two reasons why I prefer to work on Krita:

- first I am an absolut beginner in computer graphics and I want to learn some basic things about computer graphics. Krita is still really unfinished and a lot of very basic things are still missing. This gives me the possibility to code some basic stuff like scaling algorithms or simple filters. GIMP is already very advanced and there is nothing I could do to improve it.

- second I want to learn some C++ and Krita is written in C++.

I hope you understand this and I hope someone can give me a hand with finding the scaling algorithms in the GIMP source code,

Greetings, Michael