cosell@cosell.bbn.com (Bernie Cosell) (11/10/87)
Does anyone have the formulae for converting Red/Green/Blue color specs to and from Hue/Saturation/Value specs? Also, does anyone have the equation for converting color->grayscale? Thanks /Bernie\ Bernie Cosell Internet: cosell@bbn.com Bolt, Beranek & Newman, Inc USENET: bbn.com!cosell Cambridge, MA 02238 Telco: (617) 497-3503
thom@hpfcdq.HP.COM (Tom Morrissey) (11/12/87)
For a complete answer to your questions see "Fundamentals of Interactive Computer Graphics", J.D. Foley and A. van Dam, Addison-Wesely 1983, chapter 17, pgs 593-623. There is pseudo-code on pages 615 and 616 for the HSV<->RGB conversions. A fairly standard RGB->I conversion is: 0.3*red + 0.59*green + 0.11*blue Which is derived from the NTSC mapping and is used in the graphics interface standards. -- Tom Morrissey UUCP: hplabs!hpfcla!thom ARPA Internet: thom%hpfcla@hplabs.HP.COM USPS: HP/TWO, 3404 E. Harmony Rd., Bldg 1U-73, Fort Collins, CO 80525-9599 PHONE: 303-229-2869 FAX: 303-229-2692 (with attn: Tom Morrissey, MS 1U-73, x2869)
3ksnn64@pur-ee.UUCP (Joe Cychosz) (11/13/87)
In article <6781@bbn.COM> cosell@bbn.com.UUCP (Bernie Cosell) writes: > >Does anyone have the formulae for converting Red/Green/Blue color >specs to and from Hue/Saturation/Value specs? Also, does anyone >have the equation for converting color->grayscale? Thanks RGB to grayscale: Y = .59*R + .11*G + .33*B RGB to/from HSV: This is discussed in Foley and Van Dam book "Fundementals of Interactive Computer Graphics."
falk%peregrine@Sun.COM (Edward Falk) (11/14/87)
In article <7018@pur-ee.UUCP> 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes: > > >RGB to grayscale: > > Y = .59*R + .11*G + .33*B > EEEEAAAAAYYYYAAAGGGGHHH!!!! This is WRONG! Your numbers don't even add up to 1.0 Y = .30*R + .59*G + .11*B Look at a chart someday that describes the eye's sensitivity to the three colors. You'll see that blue is the least sensitive. Film has a different spectrum, which is why blue objects in a B&W picture look lighter than you remember them. -ed falk, sun microsystems sun!falk, falk@sun.com I'll take a drug test when Oliver North takes a lie detector test.
garyc@tekecs.TEK.COM (Gary Combs) (11/16/87)
You might look in the text "Fundamentals of Interactive Computer Graphics" by Foley and Van Dam at pages 615-616. -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Gary Combs garyc@tekecs.GWD.TEK Tektronix, Inc. Wilsonvile, Oregon - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
daveb@cbmvax.UUCP (Dave Berezowski) (01/21/88)
In article <7018@pur-ee.UUCP> 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes: >In article <6781@bbn.COM> cosell@bbn.com.UUCP (Bernie Cosell) writes: >> >>Does anyone have the formulae for converting Red/Green/Blue color >>specs to and from Hue/Saturation/Value specs? Also, does anyone >>have the equation for converting color->grayscale? Thanks > > >RGB to grayscale: > > Y = .59*R + .11*G + .33*B > >RGB to/from HSV: > > This is discussed in Foley and Van Dam book "Fundementals of > Interactive Computer Graphics." A more accurate formula is: White = .299*R + .587*G + .114*B