inline text by tcolorbox

Question

\documentclass[a4paper]{article}
\usepackage[most]{tcolorbox}
\usepackage{xeCJK}
\setCJKmainfont{SimSun}

\begin{document}

% Code Block I %
MM%
\begin{tcolorbox}[blankest, nobeforeafter,bottom=0pt,boxsep=0pt, opacitytext=0.2]
  \color{red}MM
\end{tcolorbox}%
MM\\
%%%%%%%%%%%%%%%%%%%%%%%%%%

% Code Block II %
MM%
\begin{tcolorbox}[blankest, nobeforeafter,bottom=0pt,boxsep=0pt, opacitytext=0.2]
  \color{red}地方
\end{tcolorbox}%

\end{document}

From the "code block I", I want to get six continuous characters "M". However, the typeset gives unwanted whitespace. I think this is because the width of tcolorbox is default of \textwidth. How can I get a tcolorbox which width changes with its content?

From the typeset of "code block II" which contains non-ascii characters(here is CJK,for example), we can see that there is unalignment in height between characters. How to align ascii characters with CJK characters?

PS: I know \tcbox may be a soluntion. But I want line-break sometimes. So tcolorbox must be choosed.

Answer 1

You don't need tcolorbox (which creates boxes and so make line breaking difficult) only to get colored, transparent text.

\documentclass[a4paper]{article}
\usepackage{pgf,xcolor}

\begin{document}

MM%
\textcolor{red}{MM}%
\textcolor{red}{\pgfsetfillopacity{0.5}MM\pgfsetfillopacity{1}}
MM

\end{document}

opacity settings don't respect tex groups, so you must reset them explictly.