[Tex/LaTex] Remove padding in table with images

Question

I have a table with 2 small images in each cell.
I reduced the horisontal padding with

\setlength{\tabcolsep}{0pt}

But I still have a white vertical space between a table separation line and images (beneath the image).
All tipps that I found are about making the space bigger.

But how can I remove that vertical padding?

How can I remove the horizontal space between the images?

\begin{table*}[t]
\begin{center}
\caption{Comparison of the form and position}
\setlength{\tabcolsep}{0pt}
\begin{tabular}{|c|}
\hline
\multicolumn{7}{|c|}{-2.5 cm} 
\\ \hline
\includegraphics[height=27mm]{image1.png}
\includegraphics[height=27mm]{image2.png} \\ \hline
$\varphi$=0.5, 126 m/s \\ \hline
\end{tabular}
\end{center}
\end{table*}

Answer 1

The interrow padding is because the bottom of an image is on the baseline and the tabular rows take into account the possible depth of descenders.

We can remove the white space by lowering the images on the top row. A similar trick can be used to have a symmetric padding above the images.

\documentclass{article}
\usepackage{graphicx}
\usepackage[export]{adjustbox}
\usepackage{siunitx}
\sisetup{per-mode=symbol}
\begin{document}
\begin{center}
\begin{tabular}{@{}c@{}}
\hline
\\[-\ht\strutbox]
\includegraphics[height=27mm,raise=-\dp\strutbox]{example-image-a}
\includegraphics[height=27mm,raise=-\dp\strutbox]{example-image-b} \\
\includegraphics[height=27mm]{example-image-a}
\includegraphics[height=27mm]{example-image-b} \\ \hline
$\varphi=0.5, \SI{126}{\meter\per\second}$ \\ \hline
\end{tabular}
\end{center}
\end{document}