These commands configure the way LaTeX searches the file system for the graphic.
The behavior of file system search code is necessarily platform dependent. In this document we cover GNU/Linux, Macintosh, and Windows, as those systems are typically configured. For other situations consult the documentation in grfguide.pdf, or the LaTeX source, or your TeX distribution’s documentation.
© 2007–2018 Karl Berry
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http://latexref.xyz/Graphics-package-configuration.html