Pack images into PDF

Question

I have many screenshots which were all taken under the same conditions: Same display resolution, same display scaling, PDF viewer at the same size, PDF zoom level the same, etc.

They are of different width and height. The widest ones have normal text width of DIN A4 paper (portrait).

I want them to be put into a PDF (paper size: DIN A4, portrait) but not one per page like

convert * output.pdf

would do but with as many as possible per page. Order matters (alphanumerical order of the file names; The files are named {1..n}.png.). The images shouldn't be stretched out in width to match the text width of the PDF but should instead all have a common (constant) zoom factor.

All the images are in the PNG format.

I prefer a command-line way to achieve this so doing it repeatedly – possibly in an automated way – is easy.

Some kind of separator between the screenshots would be nice, so it's easy to see where one ends and the next one begins.

Answer 1

I waited for an answer until a few minutes before I had to have it done. Then I hacked something together which works using bash's list expansion:

\documentclass{report}
\usepackage{graphicx}
\usepackage[a4paper, total={6in, 10in}]{geometry}

\begin{document}
\includegraphics[scale=.15]{../1}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../2}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../3}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../4}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../5}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../6}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../7}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../8}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../9}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../10}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../11}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../12}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../13}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../14}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../15}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../16}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../17}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../18}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../19}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../20}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../21}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../22}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../23}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../24}\\
\rule{\textwidth}{1pt}
\includegraphics[scale=.15]{../25}\\
% [...]

\end{document}

It's super ugly as it doesn't use a loop because I don't know how to do loops in LaTeX, and one has to use bash's list expansion again or fill in the path names manually when the number of screenshots increases.

I'll accept any answer which gets the job done, too, and is ever-so-slightly less ugly.