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List:       kde-kimageshop
Subject:    Re: Linear light scaling
From:       Boudewijn Rempt <boud () valdyas ! org>
Date:       2012-03-28 18:25:50
Message-ID: 201203282025.50594.boud () valdyas ! org
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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
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