Re: [Lcms-user] Profile Simulating Color Blindness

[Kai-Uwe B. <ku...@gm...>]

Marti,

is it useful to place the matrix simply in the matrix part of a mft2 LUT?
Perhaps this would suffice building a valid XYZ abstract profile?
All other parts of the mft2 can be filled with defaults.

regards
Kai-Uwe Behrmann
                                + development for color management=20
                                + imaging / panoramas
                                + email: ku...@gm...
                                + http://www.behrmann.name


Am 07.09.05, 11:52 +0200 schrieb Marti:

>=20
> Hi,
> The matrix XYZ -
> > I'm trying to write a little application that produces ICC profiles  fo=
r
> > the simulation of color blindness (deuteranopia and protanopia).=20
>=20
> I think the correct way to deal with that would be to build an
> abstract XYZ -> XYZ profile holding the simulation. In this
> way you got no dependencies on any RGB space.
>=20
> XYZ can be readily obtained by chaining XYZ to LMS and LMS to XYZ matrice=
s.
> You need not RGB anymore because all that is handled by the input/output
> profiles.  A multiprofile transform may be used latter to obtain the RGB =
->
> RGB, by means of icclink, for example.
>=20
> As additional benefit you are not restricted to RGB anymore.
>=20
> For bulding such abstract profile, you need a something like:
>=20
> hProfile =3D cmsOpenProfileFromFile("abstract.icc", "w");
> AToB0 =3D cmsAllocLUT();
> cmsAlloc3DGrid(AToB0, GRID_POINTS, 3, 3);
> cmsSample3DGrid(AToB0, Forward, NULL, 0);
> cmsAddTag(hProfile, icSigAToB0Tag, AToB0);
> cmsSetColorSpace(hProfile, icSigXYZData);
> cmsSetPCS(hProfile, icSigXYZData);
> cmsSetDeviceClass(hProfile, icSigAbstractClass);
> cmsCloseProfile(hProfile);
> cmsFreeLUT(AToB0);
>=20
> Then, you need to write the callback:
>=20
> static
> int Forward(register WORD In[], register WORD Out[], register LPVOID Carg=
o)
> { cmsCIEXYZ XYZ;
> cmsXYZEncoded2Float(&XYZ, In);
> // ... apply here the transform XYZ =3D [M] * XYZ
> cmsFloat2XYZEncoded(Out, &XYZ);
> return TRUE;
> }
>=20
> Hope this helps
> Regards,
> --
> Marti Maria
> The littlecms project.
> www.littlecms.com
>=20
>=20
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Mit freundlichen Gr=C3=BC=C3=9Fen
Kai-Uwe Behrmann
                                + Programmierung f=C3=BCr
                                + Farbmanagement / Bilder / Panoramen
                                + http://www.behrmann.name
                                + email: ku...@gm...