Article View: sci.image.processing
Article #1026Re: Sorting RGB Palette in Intensity Order. Please Help !
From: Jeffrey Mulligan
Date: Tue, 12 Jan 1993 22:49
Date: Tue, 12 Jan 1993 22:49
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lionel@cs.city.ac.uk (Lionel Tun) writes: >pigeons@JSP.UMontreal.CA (Pigeon Steven) writes: >>NOT! >Intensity=(r+g+b)/3. >> >>The actual Intensity value is: >> >> >> Intensity:=(r*0.299)+(g*0.587)+(b*0.114) >Why is this the case? Is it related to the sensitivity of the eye >for the different primary cones, or is it to do with physics? Both. The formula reflects the sensitivity of the eye to different wavelengths (the luminosity function), in combination with the physical emission spectra of the standard NTSC phosphors. There are a lot of phosphors in use besides the "standard" ones, so if it is important, the weights need to be measured. Nit: the above formula is for luminance. What is "intensity?" >Does it mean that green is the 'dimmest' colour and blue is >the 'brightest'? Does it also mean the RGB model is not ideal? Backwards. Green has the larges weight because it makes the largest contribution to luminance. -- Jeff Mulligan (jbm@vision.arc.nasa.gov) NASA/Ames Research Ctr., MS 262-2, Moffett Field CA, 94035-1000 (415) 604-3745
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<1ie20sINNe78@charnel.ecst.csuchico.edu> <1993Jan9.134848.7175@mcclb0.med.nyu.edu> <1993Jan10.034607.26313@cc.umontreal.ca> <1993Jan12.145735.15271@city.cs>Show Full Headers
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Newsgroups: sci.image.processing Path: arc1-ca.pugleaf.net!sparky!uunet!cs.utexas.edu!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!usenet.ins.cwru.edu!agate!eos!jbm From: jbm@eos.arc.nasa.gov (Jeffrey Mulligan) Subject: Re: Sorting RGB Palette in Intensity Order. Please Help ! Message-ID: <1993Jan12.224943.20093@eos.arc.nasa.gov> Organization: NASA Ames Research Center References: <1ie20sINNe78@charnel.ecst.csuchico.edu> <1993Jan9.134848.7175@mcclb0.med.nyu.edu> <1993Jan10.034607.26313@cc.umontreal.ca> <1993Jan12.145735.15271@city.cs> Distribution: usa Date: Tue, 12 Jan 1993 22:49:43 GMT Lines: 33