Performance problem with colorspace conversion in lcms2

[Lukast dev]

Hi Dmitry,

I fixed the performance problem in this commit [1]

Basically I inspired myself by sahil's code in filters where he scales to
float colorspace.
In that case lcms2 is not needed. But I wonder if it is possible to use
lcms2 just to scale
to different color-depth without using expensive curve fitting etc.

I will check KoStreamedMath though. But the performance is really good now,
see the commit message
with numbers

[1]
http://quickgit.kde.org/?p=calligra.git&a=commit&h=932980c140d2519d5569783154e283ef197f15f9

Lukas


2013/10/9 Dmitry Kazakov <dimula73 at gmail.com>

> Hi, Lukas!
>
> I just wanted to tell you that the KoStreamedMath class internally has
> methods for converting a bunch of rgba8 pixels into rgbaf32. This is used
> inside SSE/AVX1 code to do the trick. So theoretically, you can reuse these
> methods as well.
>
> And I'm agree with Boud, that for usual RGB images you needn't do a color
> conversion using lcms and can scale and pass the image to the gmic directly.
>
>
>
> On Wed, Oct 2, 2013 at 5:03 PM, Lukast dev <lukast.dev at gmail.com> wrote:
>
>> Linear format is not needed for gmic.
>>
>> Do you have suggestions how to implement it correctly for all possible
>> colorspace formats
>> that we currently support?
>>
>> And where does this plain scaling belongs to? Pigment?
>>
>> Lukas
>>
>>
>> 2013/10/2 Boudewijn Rempt <boud at valdyas.org>
>>
>>> On Tuesday 01 October 2013 Oct 22:15:30 Lukast dev wrote:
>>> > Hi all,
>>> >
>>> > I'm working on Gmic as you know and I hit performance bottleneck
>>> > when converting Krita layers to gmic layers and back and making the
>>> whole
>>> > experience for Krita artists quite slow.
>>> >
>>> > What I'm doing -- converting Krita colorspace uchar 8-bit rgba  to
>>> float
>>> > 32-bit rgba.
>>> > I found out that the bottleneck is actually in lcms2
>>> >
>>> > There is benchmark where is roundtrip conversion rgb8-float-rgb8
>>> > You can run it at
>>> > "build/calligra/krita/plugins/extensions/gmic/tests/KisGmicBenchmark
>>> > testConversion"
>>> >
>>> > Source:
>>> >
>>> calligra/krita/plugins/extensions/gmic/tests/kis_gmic_benchmark.cpp::testConversion()
>>> >
>>> > From the valgrind log [1] we can see that the bottleneck (98% of time)
>>> is in
>>> >
>>> > KoColorSpace::convertTo
>>> > and there in
>>> > cmsDoTransform
>>> >
>>> > and there it looks like it is using a lot of math pow, exp per pixel
>>> which
>>> > is of course slow.
>>> > For 3840x2400 image it takes 6,5 second to convert from rgba8 to rgba32
>>> > float on my laptop.
>>> >
>>> > I wrote this hack to convert Krita pixels from rgba8->rgba32 float:
>>> > http://paste.kde.org/p19eeee78/
>>> >
>>> > It takes 120 ms to convert Krita layer to gmic with this hack way, so
>>> it's
>>> > 60-times faster.
>>> >
>>> > Of course it ignores all rendering intends and profile, but I wonder if
>>> > there is some way to tell
>>> > lcms2 to do it stupidly and simply and avoid stuff like: pow, exp1 per
>>> > pixel and cmsEvalToneCurveFloat?
>>>
>>> I don't think so -- it's exactly what LCMS is doing. But I think that
>>> for G'Mic, a plain scaling of rgb u8 to rgb f32 is actually better than
>>> going through lcms and actually converting the colorspace.
>>>
>>> That is -- unless G'Mic needs the f32 data in linear format? If that's
>>> needed, you really need to use the proper profiles and let lcms do the
>>> conversion.
>>>
>>> >
>>> > [1] valgrind log
>>> > https://www.dropbox.com/s/wvazoys09p0ujtb/callgrind-convert-to.tgz
>>> >
>>> > Lukas
>>> --
>>> Boudewijn Rempt
>>> http://www.valdyas.org, http://www.krita.org,
>>> http://www.boudewijnrempt.nl
>>>
>>> _______________________________________________
>>> Krita mailing list
>>> kimageshop at kde.org
>>> https://mail.kde.org/mailman/listinfo/kimageshop
>>>
>>
>>
>> _______________________________________________
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>>
>>
>
>
> --
> Dmitry Kazakov
>
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>
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