Web images from beamer slides include the whole slide (sort of)

[prowlett]

I can't remember when it started, but for a while now chirun has been including the whole slide when converting images in beamer into images on the web.

For example, this code

\documentclass{beamer}
\setbeamercolor{background canvas}{bg=yellow}
\usepackage{tikz}
\begin{document}
    \begin{frame}
        \begin{tikzpicture}
            \draw[fill=violet] (0,0) rectangle (1,1);
        \end{tikzpicture}
    \end{frame}
\end{document}

makes a slide that looks like this:

I would expect the web version to be just a purple square with no yellow, but it does this.

(It does the same even if the background is not coloured, I just did some extreme colours to show what is happening.)

Note that this is not just reproducing the slide - the placement of the square is different.

Also if I include text on the slide this kind of thing happens:

\documentclass{beamer}
\setbeamercolor{background canvas}{bg=yellow}
\usepackage{tikz}
\begin{document}
    \begin{frame}
        Here is a purple square:
        
        \begin{tikzpicture}
            \draw[fill=violet] (0,0) rectangle (1,1);
        \end{tikzpicture}
    \end{frame}
\end{document}

produces this slide

and the web version looks like this:

This is particularly bad with multiple images. For example I have stuff like this (with less extreme colours!):

\documentclass{beamer}
\setbeamercolor{background canvas}{bg=yellow}
\usepackage{tikz}
\begin{document}
    \begin{frame}
        Here are some squares: 
        
        \begin{columns}[T]
            \begin{column}{0.25\linewidth}
                \begin{tikzpicture}
                    \draw[fill=violet!20] (0,0) rectangle (1,1);
                    \node at (0.5,0.5) {A};
                \end{tikzpicture}
            \end{column}
            \begin{column}{0.25\linewidth}
                \begin{tikzpicture}
                    \draw[fill=violet!20] (0,0) rectangle (1,1);
                    \node at (0.5,0.5) {B};
                \end{tikzpicture}
            \end{column}
            \begin{column}{0.25\linewidth}
                \begin{tikzpicture}
                    \draw[fill=violet!20] (0,0) rectangle (1,1);
                    \node at (0.5,0.5) {C};
                \end{tikzpicture}
            \end{column}
            \begin{column}{0.25\linewidth}
            \begin{tikzpicture}
                \draw[fill=violet!20] (0,0) rectangle (1,1);
                \node at (0.5,0.5) {D};
            \end{tikzpicture}
            \end{column}
        \end{columns}
    \end{frame}
\end{document}

produces a slide like this

and the web version looks like this