Linear light scaling

[Boudewijn Rempt]

On Wednesday 28 March 2012 Mar, Martin Renold wrote:
> hi Boud
> 
> On Wed, Mar 28, 2012 at 06:08:36PM +0200, Boudewijn Rempt wrote:
> > 
> > I tested today in krita -- it's a little known thing that Krita supports a
> > linear-light workflow perfectly well.  Basically, it's a matter of using
> > the right icc profile to define the working space and the example Andrew
> > showed just works in Krita.
> 
> I did certainly notice this feature :-) I have been testing this against the
> "linear light" branches of MyPaint.  It's nice to have a second
> implementation to compare with, when developing.
> 
> However I noticed something: Krita seems to zoom the display always in sRGB.

Right -- the zooming is done in the display code, after the image has been converted to the display profile. We never realized it would have this effect when we chose to implement the opengl and qpainter canvas this way.

Same with rotation.

> The linear-light branch from MyPaint isn't perfect in this respect, neither:
> it does most of the zooming (namely, the mipmap) in linear light, but the
> final step (IIRC the final 0%-49% zoom + rotation) is done in sRGB.
> 
> For me the main selling point of linear light, which changed my opinion
> from "nice to have" to "must have", was the prominent difference that it
> makes for thin white ink strokes on black background when zoomed out[1]. 
> I have even seen this on a printed image - a line that you have barely
> noticed on the screen can suddenly become prominent.
> 
> In Krita, I created a 16bpc image with the profile labeled "linear light". 
> I painted a couple of tiny white lines on pure black, and when I zoom out
> the displayed image becomes clearly too dark.
> 
> So I was wondering if this is a known limitation? Or is there a way to
> change this behaviour already?

No... And it would be very hard to actually fix this. Not something we can do for the next release, or even the one after. And it's a pity, because as you say, it's a very real limitation.

> 
> 
> [1] http://maxy.homeip.net/misc/linear_light_scaling.ogv
> 
> 


-- 
Boudewijn Rempt
http://www.valdyas.org, http://www.krita.org, http://www.boudewijnrempt.nl