Quick and dirty method for creating spot colours in PDFs


Just a 10-minute hack to explore putting spot colours into a PDF via pdf_colorstack nodes. I don’t have access to Acrobat Professional at the moment to check the separations properly, so treat this as an “alpha” method (i.e., not fully tested…). The colour defined below is lifted straight from an early PDF specification and implemented via LuaTeX nodes. As it says “on the tin”: a quick and dirty method :-).


\directlua {

n = pdf.immediateobj("stream", "{ dup 0.84 mul
exch 0.00 exch dup 0.44 mul
exch 0.21 mul
}", "/FunctionType 4
/Domain [0.0 1.0]
/Range [0.0 1.0 0.0 1.0 0.0 1.0 0.0 1.0] ")

o = pdf.immediateobj("[ /Separation
/DeviceCMYK".." "..n.." 0 R]")

pdf.pageresources =  " /ColorSpace << /LogoGreen "..o.." 0 R >> "

pdf_colstart = node.new("whatsit","pdf_colorstack")
pdf_end = node.new("whatsit","pdf_colorstack")

pdf_colstart.data="/LogoGreen  CS  /LogoGreen cs 1  SC  1 sc "

pdf_end.data= " "
pdf_end.cmd = 2

tex.box[1999]= node.hpack(pdf_colstart) 
tex.box[2000]= node.hpack(pdf_end) 



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Resulting PDF

As usual, through the Google Docs viewer or download here.