[NTG-pdftex] \pdfximage : is there a transparency attribute or method ?

Philip Taylor (Webmaster, Ret'd) P.Taylor at Rhul.Ac.Uk
Tue Jan 4 22:39:27 CET 2011



Heiko Oberdiek wrote:

 > The PDF specification knows a decode array, see section
 > "Decode Arrays" in chapter "4.8.4 Image Dictionaries".
 > pdftex.def supports it by option decodearray,
 > added in version 2010/09/09 v0.05a
 >
 > Example:
 >
 > \documentclass[a4paper]{article}
 > \usepackage{graphicx}
 > \begin{document}
 > \includegraphics[
 >    decodearray=.5 1 .5 1 .5 1
 > ]{thai-an-logo-no-phone}% image with RGB colors
 > \end{document}
 >
 > Yours sincerely
 >    Heiko Oberdiek

Thank you, Heiko : would you have any idea how to express
this using just PdfTeX primitives ?  I do not use LaTeX
for ever-day work.  My current code looks like this
(relevant parts only)

%\pdfimageapplygamma = 1
%\pdfgamma = 2200

\immediate \pdfximage width \hsize {TA-logo.png}
\setbox 0 = \vtop {\pdfrefximage \pdflastximage}
\box 0
\kern -\vsize

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