rotating & shearing

[Casper Boemann]

> That is true, I don't know your code. Your old transform visitor did 
> scaling &
> rotating/shearing with the same algorithm. But, if I remember correctly, 
> this
> prevents the optimizations I made in the scaling code. I rather prefer to
> different algorithms for scaling, rotating/shearing then one algorithm 
> that
> does everything & is hard to understand & hard to optimize. Is your 
> algorithm
> still only one function that performs scaling and rotating/shearing or do 
> you
> have different functions for that now?
It still does it in one function, but please keep in mind that rotating is 
nothing more than a combination of scaling and shearing.

And I have several optimisations in mind.


>> To an extent the colorspace independence is what makes it slow.
>
> I personally use Krita to rescale my digital photos (2272 x 1704 to
> something). For this I need fast & good scaling. If your algorithm is
> considerably slower / the quality is not as good, I will probably start 
> using
> gimp again. I think scaling images is so central, it should be really as 
> fast
> as possible & and also very good quality.
Don't worry. The new code will become as fast or faster than the old.
And the quality will be the same, Any current difference is a bug. The 
overall algorithm is the same. And rotating and shearing will be even 
greater quality.

Maybe not in 1.5 but then perhaps in 1.5.1

> I would volunteer to work on my old code. My idea is to use different code
> paths for 8 bit colormodels and the rest. That means, for 8bit RGB/CMYK 
> the
> old algorithm would be used, but for other colorspaces a version that uses
> mixing functions from the colorspaces. This way scaling RGB/CMYK images 
> would
> be as fast & good as before, but the scaling routine would still be
> colorspace independent.
That wont work. You have n way of knowing when to use theold algorithm and 
when not to.

> But I don't want to work on something that gets replaced anyway. So please 
> let
> me know if you intend to replace my scaling code anyway. And please let me
> know before you do any commits, so that I can keep a private copy of my 
> code
> (don't really want to go back to using gimp for my digital photos, so I
> better keep a private copy in this case).
Yes as requested by boudewijn I intend to replace scaling as well