GNOME Bugzilla – Bug 343576
Lanczos resize not "the best"
Last modified: 2008-01-15 14:06:52 UTC
1. Create a big image (around 3000px x 2000px) 2. Add a text layer, us a small text, preferbly a non-standard font, text layer shoudl be around 70-80px high. (ie. http://www.fontpool.com/samples/linotype/linotype_zapfino/familyid/5970/4/default.gif?width=350 http://www.fontpool.com/samples/gideon/passions_conflict/familyid/50035/4/default.gif?width=170 ). 3. Resize down to 1024x... or similar, using Lanczos. 4. Undo resize, and reapeat using cubic. 5. Comapre Results, Lanczosc producesz jaggy text, Cubic makes it look normal.
Actually, there should be no difference at all when scaling down. But the Lanczos implementation is known to be buggy and will most likely be removed unless someone fixes it really soon now.
We need to look at this before the 2.4 release. Lanczos scaling absolutely needs to work or it will only confuse people.
Oops, didn't meant to change the status. Changing it back...
I can retry the procedure with the newest release, or maybe CVS (if it's accesible), and tell you the results. Maybe I'll be able to compile with EXIF support now.
It seems to me that the summary says it all: Lanczos is not "the best" in all situations. In effect, Lanczos is something like cubic plus a bit of unsharp-mask. That is helpful in many situations but not in all, particularly when downscaling. The first thing that needs to be done, then, is to remove "best" from the menu of interpolation options, which I have done. For this bug report, I think that is probably enough. Note that there are other bug reports concerning Lanczos (particularly bug #167956) that remain open and urgently need to be solved for 2.4. I will leave this open for now, but will resolve as FIXED soon unless somebody objects.
2006-08-22 Bill Skaggs <weskaggs@primate.ucdavis.edu> * libgimpbase/gimpbaseenums.c: Don't label Lanczos as "best". Addresses bug #343576.
2006-08-23 Sven Neumann <sven@gimp.org> * libgimpbase/gimpbaseenums.h: do the change for bug #343576 here; the .c file is generated. Shouldn't we put the label "(Best)" back on the Cubic interpolation method then? Or, alternatively, remove "(Fastest)" from None?
Well, I'm not an expert on this stuff, but it looks to me like Lanczos often *is* the best when you're scaling up, at least with photographs. I would agree with removing (Fastest) from None, though, since in the absence of labels on other things, it could make it seem like None is the "best". I wonder if we could put tooltips on these things that would allow more useful explanations?
No, we can't put tooltips on items in combo-boxes. I will remove (Fastest) from "None" then and also add a translation context there.
Closing as FIXED. The remaining issues with Lanczos are better dealt with in bug #167956. Note that the following change was made to HEAD without comment here: 2006-08-23 Sven Neumann <sven@gimp.org> * libgimpbase/gimpbaseenums.[ch]: removed "(Fastest)" from "None" and added translation context (bug #343576).