First, I'd like to remove the space above the first line due to \baselineskip. This variable can't be given a value lower than the font size. It crashes saying something like "wrong units".
Here is my MWE:
\documentclass[a4paper]{article}
\usepackage[verbose,vmargin=20mm,hmargin=20mm]{geometry}
\usepackage{fontsize}
\usepackage{graphicx}
\setkeys{Gin}{keepaspectratio}
\pagestyle{empty}
\changefontsize{24}
\setlength{\parindent}{0pt}
\renewcommand{\familydefault}{\sfdefault}
\begin{document}
\includegraphics[height=70mm]{example-image-10x16}
\hfill
\includegraphics[height=70mm]{example-image-10x16} \
\begin{center}
\begin{bfseries}
{\LARGErrr My title}\
\end{bfseries}
\end{center}
\end{document}
Here between the bottom of the images and the top of "My title" there's a space due to the font size set by \changefontsize. Also if I use \centering instead on \begin{center} ... \end{center} that space vanishes. If anybody could explain it. If I remove any centering effect (neither use of \begin{center} ... nor of \centering) then the space is reduced to half.
Underfull \hbox (badness 10000) in paragraph at lines 15--18latex is warning you about the misplaced\\(which should never be at the end of the paragraph) and is forcing the spurious blank line (not a vertical space) that you are asking about. – David Carlisle Aug 15 '22 at 11:48LaTeX Font Warning: Size substitutions with differences (Font) up to 22.82007pt have occurred.usefix-cmpackage. – David Carlisle Aug 15 '22 at 11:50\centering: As you noticed, this command just center the text whereas the center environment also add some space before and after the text. There are nothing more to explain. The command and the environment is not one the same hairy beast. – Fran Aug 16 '22 at 21:11