RGB 16 bit as default when starting Krita

[Boudewijn Rempt]

On Wednesday 20 January 2010, Martin Renold wrote:
> On Wed, Jan 20, 2010 at 06:56:27PM +0300, Dmitry Kazakov wrote:
> > This means that you must convert an image to sRGB before publishing in
> > web. Are you going to inform every user about that?
> 
> That might not be an option for Krita, but in case you're interested, in
> MyPaint, I simply don't.  I always convert to sRGB when saving, and enjoy
> 16bpc mainly for the brush engine.  The problem with 8bpc is that you can
> often see the accumulated numerical error by eye.  Here is a GIMP bugreport
> of the problem that 16bpc solves for painting:
> 
> https://bugzilla.gnome.org/show_bug.cgi?id=588681
> 
> Depending on how brushes work, it might not be a real problem (eg. if you
> have only high opacity dabs).

Well, the ball got rolling when I remarked on #lgm that using the mypaint 
brush engine in Krita (which is not working yet!) would always cause 
conversions to happen unless the user was working in 16 bit rgba.

Right now, Krita has two basic painting modes: direct and indirect. When 
painting direct, opacity is way too high to notice the effect. But it's also 
too high to be useful, there must be something wrong there. When painting 
indirect, strokes never build up, so the issue isn't visible. When using the 
airbrush, it's noticeable that it doesn't work correctly :-). We need to fix a 
bug there and then maybe it will be clear whether we suffer from that gimp 
issue as well in 8 bit mode.

> 
> > Third. You must use 16 bit or float for scRGB. Do you think degrading
> > performance twice worth [...]
> 
> If you don't mind a non-Krita developer commenting: I would not be very
> surprised if a high quality operation with all the proper rounding and
> dithering in 8bpc is actually slower than doing the same in 16bpc with
> straight forward math.  Of course much also depends on how carefully
> optimized it is, and my guess might also be wrong.

It's certainly something we will need to measure in Krita. But we'll also have 
to work to optimize the number of copies we do and the algorithms we use. 
 
> On another point in this thread, I did write in my blog post that I found
> painting in linear light counter-intuitive.  I should add that I tried it
> only for a few hours, and some people who also tried it (with other
> programs) strongly disagree with me.  I did not take enough time to get
> used to it first, maybe I would have liked it in the end (or not).

Ah :-) Well, Krita is a KDE app, so users can choose whether to use linear 
light or not. Right now, I am tending towards not making it default.
-- 
Boudewijn Rempt | http://www.valdyas.org