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Function Reference
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The array of colorant names must correspond, in order, to the components of the process color
space. For example, an RGB color space must have three names corresponding to red, green, and
blue. The names may be arbitrary (that is, not the same as the standard names for the color space
components) but must match those specified in the DeviceN color space, even if not all components
are present in the DeviceN color space.
The defintion of process colorants of a DeviceCMYK color space is optional since the colorant names
Cyan, Magenta, Yellow, and Black are always considered as color components of a DeviceCMYK
color space.
How to create the PostScript Calculator Function?
A PostScript calculator function is represented as a string containing code written in a small subset
of the PostScript language. The language that can be used in a PostScript calculator function
contains expressions involving integers, real numbers, and boolean values only. There are no
composite data structures such as strings or arrays, no procedures, and no variables or names.
The following operators are supported in a PostScript calculator function:
Operator type
Operators
Arithmetic operators
abs
cvi
floor
mod
sin
add
cvr
idiv
mul
sqrt
atan
div
ln
neg
sub
ceiling
exp
log
round
truncate
cos
Relational, boolean,
and
false
le
not
true
and bitwise operators
bitshift
ge
lt
or
xor
eq
gt
ne
Conditional operators
if
ifelse
Stack operators
copy
exch
pop
dup
index
roll
For more information on these operators, see Appendix B of the PostScript Language Reference,
Third Edition. The operand syntax for PostScript calculator functions follows PDF conventions
rather than PostScript conventions. The entire code defining the function is enclosed in braces { }.
Braces also delimit expressions that are executed conditionally by the if and ifelse operators:
boolean { expression } if
boolean { expression1 } { expression2 } ifelse
This construct is purely syntactic; unlike in PostScript, no "procedure objects" are involved.
When executing the function, the application pushes first the tint values of the setcolor operator or
the corresponding image components on the stack. The function is then executed and the remaining
 

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