🚀 go-pugleaf

In article <1992Dec28.000443.7228@hot.com> Robert_La_Ferla@hot.com writes:

   How does one create a gold tone in PostScript?  I realize that gold is  
   a metal and to create it you need to either render it or use a gold ink  
   but I'm looking for a simpler way to achieve the same effect.  I have  
   some artwork containing gold arcs and lines which will be printed on a  
   Canon CLC color laser printer.  Note that the artwork is pure  
   PostScript and was not created using an application.

   Is there a combination of CMYK values that approximates a gold  
   tone?  Is there a sample of a rendered gold image that I could use as  
   a fill pattern?  How would I do the latter?

   Robert La Ferla
   Hot Technologies

Gold is yellow plus the impression that the surface is
`metallic'/`specular', just as silver is white/grey plus an impression that
the surface is `metallic'/`specular'.  You cannot create the impression of a
metallic color merely by manipulating RGB or CMYK at a pixel. Context is
important. 

Surfaces with a specular component of reflection can sometimes be discerned
because of strong localized high-lights, particularly high-lights that
change in position as the viewer (or the light source) moves.  In other 
words, the way to get the impression of `gold' or `silver' is to create a
suitable spatial distribution of light and dark, preferrably with
a large dynamic range.  The best impression of `gold' would be in the
portrayal of a curved surface, where most of the surface is shown as black,
with one or more near parallel narrow streak of light yellow, with the
brightness varying within in the sreak from the edge towards the center.



Berthold K.P. Horn
Cambridge, Massachusetts, USA