Hi, Additionally attched a view at the *b channel of the generated CLUT. Hue and Saturation where changed. Maybe this explains the funny results?
Brightness and Contrast works more explainable to me.
regards
Kai-Uwe Behrmann
+ development for color management
+ imaging / panoramas
+ email: [EMAIL PROTECTED]
+ http://www.behrmann.name
Am 13.05.05, 23:32 +0200 schrieb Dirk StrÃker:
> Hi,
>
> great it works. I like the changing of the hue-value, funny results. ;-)
>
> Wouldn't it be good to make the saturation somehow multiplicative
> so that all will be gray by applying the value "0"? Cout = Cin * Saturation?
> I'm sure that this is mathematicaly not correct but maybe... ;-)
>
> Thanks, I go playing with my colors
>
> Dirk
>
> > Hi,
> >
> > This function is just a very simple way to modify
> > Bright, Contrast, Hue, Saturation and white point.
> >
> > It works on Lab colorspace, so there is still a lot
> > of room for improvement. However, it works fine
> > for most situations.
> >
> > The mechanics are simple, a Lab -> Lab profile is
> > computed by using following sequence
> >
> > 1) Input Lab is converted to LCh
> >
> > 2) LCh is modified by using:
> > Lout = Lin * Contrast + Brightness
> > Cout = Cin + Saturation
> > hout = hin + hue
> >
> > 3) The resulting LCh is converted back to Lab
> > and that is the output.
> >
> > So, the range of parameters would be
> >
> > Contrast : Something between 0 ... 2, 1 for don't change
> >
> > Brightness: Something between -100 and 100. Those are
> > extreme values, so probably -25 to 25 is more adequate.
> > 0 for don't change
> >
> > Saturation: Strictly, that is Colorfulness, -25..25 or more.
> > 0 for don't change
> >
> > Hue: can be up to -180..180 but those are huge values.
> > Small endings would make more sense, something like
> > -15 .. 15. 0 for don't change.
> >
> > For the whitepoints, both are the temperature in ÂK of
> > the blackbody locus. 5000=D50, 6504 = D65 and so.
> >
> > Once you have obtained the abstract profile, you can
> > concatenate into workflow by using Multiprofile transforms.
> > i.e.
> >
> > sRGB -> Abstract -> sRGB
> >
> > And in this way you can modify Bright, Contrast, etc of
> > sRGB values. This works on other spaces, like CMYK too.
> >
> > Hope this helps
> > --
> > Marti Maria
> > The littlecms project.
> > www.littlecms.com
> >
> >
> > ----- Original Message -----
> > From: "Dirk StrÃker" <[EMAIL PROTECTED]>
> > To: <lcms-user@lists.sourceforge.net>
> > Sent: Wednesday, May 11, 2005 9:19 PM
> > Subject: [Lcms-user] Value range for BCHSWabstractProfile
> >
> > > Hi,
> > >
> > > I would like to work with the "cmsCreateBCHSWabstractProfile"-function in
> > > order to use it as an in-between profile to change contrast, hue etc. But
> > > I
> > > wonder what the value range for "Bright", "Contrast" and "Saturation"
> > > would
> > > be? For "hue" I think it is 0..360 degrees, am I right?
> > > In the API it is noted, that negativ values are possible, what does this
> > > mean,
> > > how does it work? Do I lower the brightness, for example, with negative
> > > values for "Bright"?
> > >
> > > Greetings
> > > Dirk
> > ><<attachment: correctio2_screenshot.jpg>>
