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

[Heiko Oberdiek]

On Tue, Jan 04, 2011 at 09:39:27PM +0000, Philip Taylor (Webmaster, Ret'd) wrote:

> 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}
> 
> Thank you, Heiko : would you have any idea how to express
> this using just PdfTeX primitives ?

pdftex.def tells you (also graphicx could be used in plain TeX using
miniltx.tex):

\usepackage{graphicx}
\let\orgpdfximage\pdfximage
\def\pdfximage#1#{%
  \typeout{\string\pdfximage\space#1{...}}%
  \orgpdfximage#1%
}

> \immediate \pdfximage width \hsize {TA-logo.png}

\immediate\pdfximage
  width\hsize
  attr{/Decode[.5 1 .5 1 .5 1]}%
  {TA-logo.png}%

Yours sincerely
  Heiko Oberdiek
--