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What is the way to force \includegraphics to use specific file extension for all document?

If I have in the folder figure.pdf and figure.png

\includegraphics{figure} command will use figure.png, if I need *.pdf I could force to use it by typing: \includegraphics{figure.pdf}

But if I need sometimes to compile document with all figures with png extension or pdf, what should I change in graphics package settings?

marked as duplicate by egreg, Zarko, Paul Gaborit, Community Dec 13 '15 at 15:54

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