Define a single background with beamer in LaTex

Question

I am using the Singapore theme in Beamer for multiple reasons (this theme is kind of clean, without too much vertical/horizontal bar everywhere, progress dots, ...) and so, I would like to keep it.

Anyway, I defined a back ground with tikz with a circular color gradient background for slide content. But, the header is defined with a background too and I can't suceed to remove its background (even after 2 hours in internet lol).

Here is a mwe where you can see the difference between the two background which make an horizontal white line that I do not want.

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usepackage{lipsum}

\usetheme{Singapore}

\begin{document}
\usebackgroundtemplate{
  \begin{tikzpicture}
    \path [outer color = blue!5, inner color = blue!1]
      (0,0) rectangle (\paperwidth,\paperheight);
  \end{tikzpicture}
}

\section{Section}
\begin{frame}
\lipsum[1]   
\end{frame}

\end{document}

How can I do to make the background with a circular color gradient for the fullsize of the slide ? Without interruption of the header ?

Answer 1

The Singapore theme without the colour gradient boils down to the following settings:

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usepackage{lipsum}

%\usetheme{Singapore}

\useoutertheme[subsection=false]{miniframes}
\setbeamertemplate{frametitle}[default][center]
\beamertemplatedotitem


\begin{document}
\usebackgroundtemplate{
  \begin{tikzpicture}
    \path [outer color = blue!5, inner color = blue!1]
      (0,0) rectangle (\paperwidth,\paperheight);
  \end{tikzpicture}
}

\section{Section}
\begin{frame}
\lipsum[1]   
\end{frame}

\end{document}