# black background when including pdf with transparent background as image

I have a pdf image with transparent background that I'll include by using graphicx (\includegraphics). Everything is fine when using pdfLaTeX to build my pdf, but when I switch to XeTeX the image will suddenly have black background instead of being transparent. I have tried to reproduce the problem, and quite strangely some pdf images do not exhibit this problem while some do.

My XeTeX version is 3.1415926-2.4-0.9998, which I believe is the newest. And here's a sample pdf image if any one wishes to test: https://docs.google.com/file/d/0BxDcKKtrknW_MlZMV2lKOE5oMXc/edit

Minimal code:

\documentclass[10pt]{article}
\usepackage{graphicx}
\begin{document}
\begin{figure}[h]
\centering \includegraphics[scale=0.48]{MapReduce_Pipeline.pdf}
\caption{MapReduce Pipeline.}
\label{fig:MapReduce_Pipeline}
\end{figure}
\end{document}

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The PDF file MapReduce_Pipeline.pdf contains the image as JPEG image with a transparency mask. xdvipdfmx, the PDF driver part of XeTeX seems to forget to add the the mask entry. Version 0.7.8 works under TeX Live/Linux, but fails under MiKTeX/Windows.
Alternatively you can open the image MapReduce_Pipeline.pdf with evince. There you can store (right click) the image object as PNG file (PNG has transparency feature). Then you can include the PNG image in your XeLaTeX document (the scale factor needs adjusting, or use width=\linewidth or similar).