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 ºK 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 Ströker" <[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 > > > > > > ------------------------------------------------------- > > This SF.Net email is sponsored by Oracle Space Sweepstakes > > Want to be the first software developer in space? > > Enter now for the Oracle Space Sweepstakes! > > http://ads.osdn.com/?ad_id=7393&alloc_id=16281&op=click > > _______________________________________________ > > Lcms-user mailing list > > Lcms-user@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/lcms-user > > > > > > > > -- > > No virus found in this incoming message. > > Checked by AVG Anti-Virus. > > Version: 7.0.308 / Virus Database: 266.11.9 - Release Date: 12/05/2005 ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_ids93&alloc_id281&op=click _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
