[argyllcms] Re: gamut conversion through the LUT ?!
- From: "Hal V. Engel" <hvengel@xxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 21 Jul 2008 17:13:39 -0700
On Monday 21 July 2008 03:06:11 pm lee scratchy wrote:
> yeah, I'm very confused actually :)
>
> you jsut said "the LUTs in ICC profiles are 3D", so the ICC can compute the
> right color to show on-screen.....or ?
Just to be clear if you have a correct profile for the source image(s) and a
correct profile for the display device then you can use a color management
engine to create a transform from the source color space to the display color
and you will get the correct results when that transform is allplied to the
images. But this assumes that you have a good display profile (like one
created with ArgyllCMS using a measurement device) and that you have some how
gotten a good profile for the source images (this could be problematic unless
you have control over the whole video capture chain).
>
> actually I'd like to get gamut conversion in Haali's Renderer, which is a
> D3D video renderer......is there a way to use the OpenGL renderer on top of
> it ? I kinda doubt it :(
Using gl to do colorspace conversion does not require that the gl code is used
to directly render the images. But I suspect that to do what you want you are
going to need a custom coded rendering pipe line since it is highly unlikely
that any publicly available rendering engine has the hooks needed to allow for
arbitrary color space transforms as part of the rendering pipe line and this
appears to be what you want to do.
>
> -Maxime
>
>
>
>
> From: hvengel@xxxxxxxxxxxxx: argyllcms@xxxxxxxxxxxxxxxxxxxx: [argyllcms]
> Re: gamut conversion through the LUT ?!Date: Mon, 21 Jul 2008 15:02:32
> -0700
>
> On Monday 21 July 2008 02:45:58 pm lee scratchy wrote:
> > humm OK makes sense and would explain our results :(
> >
> > so even an ICC v4 can't help ?
> >
> > I read that there is 3x3 matrixes in the v4 ICC specs ?
> >
> > http://www.color.org/createv4.pdf
> >
> > sRGB gamut after color re-rendering by the new v4 ICC profile
> > (transparent green) ... 3D CLUT = 3x3 matrix XYZ(D50) to RGB linear ...
> >
> > any idea how could I create such an ICC file ? :)
> >
> > Thanks,
> >
> > -Maxime
>
> I think you are confused. Video card LUTs are 1D but the LUTs in ICC
> profiles are 3D (or more). With 1D LUTs gamut mapping is not possible since
> the most you can do with 1D LUTs is correct the gamma and neutral point of
> the device. The 1D LUT does not have enough information to correct for
> anything beyond this. With 3D LUTs you can do things like gamut mapping and
> other colorspace conversions.
>
> It is possible to use a gl shader program to do 3D LUT color space
> conversions. But this does NOT use the video cards hardware LUTs but
> instead uses LUTs stored in the video cards general memory space. There is
> an OpenICC Google Summer of Code project that is working on adding GPU
> driven color space conversion to enable system wide CM on X11 systems. I
> believe that this project has had gl shaders doing 3D LUT color space
> conversions for some time now.
>
> > > Date: Mon, 21 Jul 2008 23:35:31 +0200
> > > From: nospam456@xxxxxx
> > > To: argyllcms@xxxxxxxxxxxxx
> > > Subject: [argyllcms] Re: gamut conversion through the LUT ?!
> > >
> > > lee scratchy wrote:
> > >> what the Pixel Shader script does is a simple 3D matrix from what I
> > >> understand :
> > >> [...]
> > >> so are you saying that this can't be done through the LUT ?
> > >
> > > Yes, a 3D matrix multiplication can't be done with one-dimensional
> > > LUTs. As I said, you need a three-dimensional LUT to accomplish what
> > > you want. But the VCGT in the graphics card is just a one-dimensional
> > > LUT :-(
> > >
> > > Regards,
> > > Gerhard
> >
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