Q:

How do I insert a full screen picture inside an itemized environment?

I'm using beamer to create slides and I would like to place a full screen picture with a black background inside an itemized environment.
What I tried so far is:
\documentclass[10pt]{beamer}
\usetheme{Szeged}
\usecolortheme{dolphin}

\usepackage{fontspec}
\usepackage{pgf}

\setbeamercovered{transparent=25}   %Uncover text transparently

\begin{document}
    \begin{frame}
        \begin{itemize}
            \item<1> first item
            \only<2>{\setbeamercolor{background canvas}{bg=black}
                \begin{figure}
                \centering 
                \includegraphics[width=.7\textwidth]{image.jpg} %here I would like to have a full screen image on black background
                \end{figure}
            }
            \item<3> second item
        \end{itemize}               
    \end{frame}
\end{document}

I would be grateful for any clue,
Mihai

A:

It is possible to use a {tikzpicture} and overlay it:
\documentclass[10pt]{beamer}
\usetheme{Szeged}
\usecolortheme{dolphin}

\usepackage{fontspec}
\usepackage{pgf}

\usepackage{tikz}

\setbeamercovered{transparent=25}   %Uncover text transparently

\begin{document}
    \begin{frame}
        \begin{itemize}
            \item<1> first item
            \item<3> second item
            \item<4> third item
        \end{itemize}
         \only<2>{
            \begin{tikzpicture}[remember picture,overlay]
             \fill [black] (current page.south west) rectangle (current page.north east);
             \node at (current page.center) {\includegraphics[scale=0.5]{example-image}};
            \end{tikzpicture}
         }
    \end{frame}
\end{document}

Result

Notes

overlay means that the {tikzpicture} doesn’t get space (a box) on the page but overlay it’s content on the already typeset part of the page
thats the reason of moving the code after {itemize}, the <> syntaxt cares for the right order
remember picture garants access to the current page node.
I guess the blue bars are shipped out as the last element of a frame. That’s why they aren’t affected by the overlay
To get the right positions compile twice.
I took an example image which is part of the mwe package.

