为什么不支持 .gif 文件？

Question 1

只是为了证明相反的观点：直接嵌入 GIF是可能，诚然不是 PDF，而是 SVG 输出。

我们只需添加一条graphicx规则，将 GIF（静态/动画）视为另一种位图格式（PNG 和 JPEG 除外），并使用用户提供的<img file base name>.xbb文件包含边界框信息：

\DeclareGraphicsRule{.gif}{bitmap}{.xbb}{}

对于 480px * 360px 的图像，文件内容xbb如下

%%BoundingBox: 0 0 480 360

为了将 GIF 数据内联到 SVG 输出中，GIF 文件必须采用 base64 编码。软件包media4svg提供了一个命令，我们利用该命令来修改graphicx位图的驱动程序代码 ( \Ginclude@bitmap)。

（需要 pkg media4svg，v0.9 2022-08-12。）

排版example.tex如下

dvilualatex example
dvisvgm --zoom=-1 --bbox=papersize --font-format=woff2 example

或者

latex --shell-escape example
dvisvgm --zoom=-1 --bbox=papersize --font-format=woff2 example

甚至

xelatex --shell-escape --no-pdf example
dvisvgm --zoom=-1 --bbox=papersize --font-format=woff2 example.xdv

注意：Firefox 无法播放嵌入在网页中的 SVG 中的动画 GIF（如 TeX.SX）。这似乎是一个错误。请改用基于 Blink 的 Web 浏览器，例如 Chromium、Chrome、Opera 或 Edge。或者（右键单击）图像以在其自己的浏览器选项卡中打开 SVG。

输入文件example.tex。

（下载 GIF 来自https://upload.wikimedia.org/wikipedia/commons/d/d3/Newtons_cradle_animation_book_2.gif）

\documentclass[dvisvgm]{article}

% download `Newtons_cradle_animation_book_2.gif' before typesetting:
%
% https://upload.wikimedia.org/wikipedia/commons/d/d3/Newtons_cradle_animation_book_2.gif

\usepackage[a6paper]{geometry}
\usepackage{graphicx}
\DeclareGraphicsRule{.gif}{bitmap}{.xbb}{}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% provide BoundingBox information in a separate .xbb file
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{filecontents}[overwrite,noheader]{Newtons_cradle_animation_book_2.xbb}
%%BoundingBox: 0 0 480 360
\end{filecontents}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% patch graphics backend driver `dvisvgm.def' to physically embed
% bitmaps into DVI
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\let\Ginclude@bitmapOrig\Ginclude@bitmap
\def\Ginclude@bitmap#1{%
  \baseSixtyFour{#1}{72}{{?nl}}\bitmap@stream%
  \Ginclude@bitmapOrig{%
    data:image/\expandafter\remove@dot\Gin@ext;;base64,{?nl}%
    \bitmap@stream}%
}
\def\remove@dot.#1;{#1}
\makeatother

\RequirePackage{media4svg} % provides base64-encode utility
\ExplSyntaxOn
\cs_new:Npn\baseSixtyFour#1#2#3#4{
  \sys_if_engine_luatex:TF{
    \xdef#4{\directlua{media4svg.base64("#1",#2,"#3")}}
  }{
    \msvg_convert_file_to_blob:nnnN{#1}{#2}{#3}#4
  }
}
\ExplSyntaxOff
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}

\section{Animated GIF}
\noindent\includegraphics[width=\linewidth]{Newtons_cradle_animation_book_2.gif}

\end{document}

Answer