Zooming in and highlighting part of picture

Question

In a beamer presentation, is it possible to zoom in on an image to make it full screen and if possible to highlight (something like illuminating a part of picture by bright light while other areas of the slide fade ) the desired location on the image?

Answer 1

This is a modification of samcarter's answer. As it stands, the zoomed image will not occupy the whole frame if a theme which installs header/footer is used or if the frame has a title. However, the beamer documentation explains how to overcome this (page 109):

\documentclass{beamer}
\usetheme{Warsaw}

\begin{document}

  \begin{frame}<1>[label=zooms]
    \frametitle<1>{Example Grid}
    \framezoom<1><2>[border](0cm,0cm)(2cm,1.5cm)
    \framezoom<1><3>[border](1cm,3cm)(2cm,1.5cm)
    \framezoom<1><4>[border](3cm,2cm)(3cm,2cm)
    \pgfimage[height=8cm]{example-grid-100x100bp.pdf}
  \end{frame}
  \againframe<2->[plain]{zooms}

\end{document}

EDIT

You could use something like the fadings library to highlight a particular area of the slide if you wished. This isn't quite what you wanted, I know, but perhaps you can modify it to provide something suitably useful:

\documentclass{beamer}
\usetheme{Warsaw}
\usepackage{tikz}
\usetikzlibrary{fadings, backgrounds}
\tikzfading[name=fade out, inner color=transparent!100, outer color=transparent!25]
\tikzfading[name=fade in, inner color=transparent!100, outer color=transparent!0]
\begin{document}

  \begin{frame}<1>[label=zooms]
    \frametitle<1>{Example Grid}
    \framezoom<1><2>[border](1cm,3cm)(2cm,1.5cm)
    \framezoom<1><3>[border](3cm,2cm)(3cm,2cm)
    \begin{tikzpicture}[outer sep=0, inner sep=0]
      \only<2>{%
        \fill [path fading=fade out, black] (-3,-.5) rectangle +(2,1.5);
      }
      \only<3>{%
        \fill [path fading=fade in, white] (-1,-.25) rectangle +(3,2.25);
      }
      \begin{scope}[on background layer]
       \node at (0,0) {\includegraphics[height=8cm]{example-grid-100x100bp.pdf}};
     \end{scope}
    \end{tikzpicture}
  \end{frame}
  \againframe<2->[plain]{zooms}

\end{document}

Answer 2

Following an example in http://de.slideshare.net/mustainmtn/beamer-guide-by-kijoo-kim-aka-daisyweb, p.32 this can easily be done:

\documentclass{beamer}

\begin{document}

\begin{frame}
    \framezoom<1><2>[border](0.5cm,0.5cm)(2cm,1.5cm) \framezoom<1><3>[border](1cm,3cm)(2cm,1.5cm) 
    \framezoom<1><4>[border](3cm,2cm)(2cm,2cm)
    \pgfimage[height=6cm]{example-grid-100x100bp.pdf}
\end{frame}

\end{document}