BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  RGB algorithms          BorlandTalk.com Forum Index -> C++ Builder (Graphics) View previous topic :: View next topic   Author Message smartdude80 Guest Posted: Wed Nov 16, 2005 8:51 pm    Post subject: RGB algorithms Whats the algorithm used to get and set luminance, saturation, and hue for a 24-bit RGB color? Back to top Bruce Salzman Guest Posted: Wed Nov 16, 2005 9:00 pm    Post subject: Re: RGB algorithms "smartdude80" <smartdude81 (AT) comcast (DOT) net> wrote Quote: Whats the algorithm used to get and set luminance, saturation, and hue for a 24-bit RGB color? http://www.dcs.ed.ac.uk/home/mxr/gfx/faqs/colorconv.faq see section 5.3 -- Bruce Back to top smartdude80 Guest Posted: Wed Nov 16, 2005 11:27 pm    Post subject: Re: RGB algorithms Quote: http://www.dcs.ed.ac.uk/home/mxr/gfx/faqs/colorconv.faq see section 5.3 -- Bruce I looked here and found what i was looking for but the hue formula looks real complicated to me: Hue = cos^(-1) [(0.5*(R-G)+(R-B)) / ( ((R-G)^2 + (R-B)(G-B))^(0.5) )] Can anyone translate this into a C expression? R, G, and B are of course red, blue, and green. Im guessing the ^ symbol means exponent but i dont know why they have cos^(-1). Back to top Bruce Salzman Guest Posted: Thu Nov 17, 2005 12:15 am    Post subject: Re: RGB algorithms "smartdude80" <smartdude81 (AT) comcast (DOT) net> wrote Quote: http://www.dcs.ed.ac.uk/home/mxr/gfx/faqs/colorconv.faq see section 5.3 -- Bruce I looked here and found what i was looking for but the hue formula looks real complicated to me: Hue = cos^(-1) [(0.5*(R-G)+(R-B)) / ( ((R-G)^2 + (R-B)(G-B))^(0.5) )] Can anyone translate this into a C expression? R, G, and B are of course red, blue, and green. Im guessing the ^ symbol means exponent but i dont know why they have cos^(-1). cos^(-1) is inverse cosine (or arccosine). double hue = acos((0.5 * (R-G)+(R-B))/sqrt((R-G)*(R-G) + (R-B)*(G-B))); -- Bruce Back to top Steve Aletto Guest Posted: Thu Nov 17, 2005 10:03 am    Post subject: Re: RGB algorithms Quote: Whats the algorithm used to get and set luminance, saturation, and hue for a 24-bit RGB color? Have a look at ColorHLSToRGB and ColorRGBToHLS: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/shell/reference/shlwapi/gdi/palette.asp HTH, Steve. Back to top smartdude80 Guest Posted: Mon Nov 21, 2005 7:52 pm    Post subject: Re: RGB algorithms Quote: cos^(-1) is inverse cosine (or arccosine). double hue = acos((0.5 * (R-G)+(R-B))/sqrt((R-G)*(R-G) + (R-B)*(G-B))); -- Bruce I wound up finding source code (that actually works) for doing this type of conversion on the internet. Thanks anyways. 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