[Tex/LaTex] hhline and cell color problems revisited

Question

So, I've read a lot of issues with cell coloring and cell border. I tried to fix them as follows:

I use hhline to print horizontal cell borders.

If I am in the middle of a multirow cell, I print hhline using the same color as the cell. This avoids having white lines in the middle.

However, I still get pale lines running through the middle of my multirow cell. They aren't white, but they are a paler color than the cell.

Here is a MWE.

\documentclass[]{article}


\usepackage{array}
\usepackage{tabularx}
\usepackage{siunitx}
\usepackage[table]{xcolor}
\usepackage{multirow}
\usepackage{hhline}

\begin{document}


This looks bad:
\begin{tabularx}{1\textwidth}{m{0.333\textwidth} m{0.333\textwidth} m{0.333\textwidth} }

\hhline{---}
\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{1}{c|}{\cellcolor[RGB]{255, 192, 203} middle} &
\multicolumn{1}{c|}{right cell} \tabularnewline

\hhline{|-|-|-|}

\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{2}{c|}{\cellcolor[RGB]{255, 165, 0} } \tabularnewline

\hhline{|-|>{\arrayrulecolor[RGB]{255, 165, 0}}-->{\arrayrulecolor{black}}|}

\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{2}{c|}{\multirow{-2}{*}{\cellcolor[RGB]{255, 165, 0} multirow cell with pale line through the middle}} \tabularnewline

\hhline{|-|--|}

\end{tabularx}


\end{document}

Is this just a problem of my particular pdf viewer? Is there a simple fix?

Answer 1

You get this sort of lines when two colored surfaces touch exactly. And the only way to get rid of them is either to ensure that the surfaces overlap a bit, to paint over the gap, or to have only one surface:

\documentclass[]{article}
\usepackage[table]{xcolor}
\usepackage{tikz}

\begin{document}

{\color{red}\rule{1cm}{1cm}\rule{1cm}{1cm}}

{\color{red}\rule{1cm}{1cm}\hspace{-0.1pt}\rule{1cm}{1cm}}    

{\color{red}\rule{1cm}{1cm}\rule{1cm}{1cm}\tikz[overlay]\draw(-1,0)--++(0,1);}

{\color{red}\rule{2cm}{1cm}}

\end{document}

Using \hhline imho doesn't help much as you then have the gaps between the lines and the colored cell. But you can e.g. move the second line a bit up:

\documentclass[]{article}
\usepackage{array}
\usepackage{tabularx}
\usepackage{siunitx}
\usepackage[table]{xcolor}
\usepackage{multirow}
\usepackage{hhline,tikz}

\begin{document}


\begin{tabularx}{1\textwidth}{m{0.333\textwidth} m{0.333\textwidth} m{0.333\textwidth} }

\hhline{---}
\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{1}{c|}{\cellcolor[RGB]{255, 192, 203} middle} &
\multicolumn{1}{c|}{right cell} \tabularnewline

\hhline{|-|-|-|}

\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{2}{c|}{\cellcolor[RGB]{255, 165, 0} } 
\tabularnewline[-0.5pt] % a a bit up.

\multicolumn{1}{|c|}{\cellcolor[RGB]{255, 255, 0} a cell} &
\multicolumn{2}{c|}{\multirow{-2}{*}{\cellcolor[RGB]{255, 165, 0}multirow cell with pale line through the middle}} \tabularnewline

\hhline{|-|--|}

\end{tabularx}


\end{document}