An RGB Device specification is identified by the prefix ``rgb:'' and conforms to the following syntax:
rgb:<red>/<green>/<blue> <red>, <green>, <blue> := h | hh | hhh | hhhh h := single hexadecimal digits (case insignificant)
Note that h indicates the value scaled in 4 bits, hh the value scaled in 8 bits, hhh the value scaled in 12 bits, and hhhh the value scaled in 16 bits, respectively.
For backward compatibility, an older syntax for RGB Device is supported, but its continued use is not encouraged. The syntax is an initial sharp sign character followed by a numeric specification, in one of the following formats:
#RGB (4 bits each) #RRGGBB (8 bits each) #RRRGGGBBB (12 bits each) #RRRRGGGGBBBB (16 bits each)
The R, G, and B represent single hexadecimal digits. When fewer than 16 bits each are specified, they represent the most significant bits of the value (unlike the ``rgb:'' syntax, in which values are scaled). For example, the string ``#3a7'' is the same as ``#3000a0007000''.
An RGB intensity specification is identified by the prefix ``rgbi:'' and conforms to the following syntax:
rgbi:<red>/<green>/<blue>
Note that red, green, and blue are floating-point values between 0.0 and 1.0, inclusive. The input format for these values is an optional sign, a string of numbers possibly containing a decimal point, and an optional exponent field containing an E or e followed by a possibly signed integer string.
The standard device-independent string specifications have the following syntax:
CIEXYZ:<X>/<Y>/<Z> CIEuvY: <u>/<v>/<Y> CIExyY: <x>/<y>/<Y> CIELab: <L>/<a>/<b> CIELuv: <L>/<u>/<v> TekHVC: <H>/<V>/<C>
All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are floating-point values. The syntax for these values is an optional plus or minus sign, a string of digits possibly containing a decimal point, and an optional exponent field consisting of an ``E'' or ``e'' followed by an optional plus or minus followed by a string of digits.