highlighting vowels using a background color

Question

Is it possible to give the letters a,e,i,o,u,y a different background color in a piece of text by using a loop or package? For instance, give the a's a red background, the e's a blue background, etc. Without changing the background of the other letters in the text.

To the extent that you are trying to distinguish vowels from consonants, a simple version will have problems with 'y'. — Alan Munn, Nov 23 '13 at 20:03
See p.14 in http://mirror.ox.ac.uk/sites/ctan.org/info/xetexref/xetex-reference.pdf Is that what you need? — Thruston, Nov 23 '13 at 20:08
Related (if not duplicate) question: Color all vowels differently in a LaTeX document — Alan Munn, Nov 23 '13 at 20:16
In fact, you seem to have the same user name. Why is the answered question not sufficient for you? — Alan Munn, Nov 23 '13 at 20:29
What's different (slightly) is the background colour. The xetex charclass solution in the referenced question changes foreground colours. — Thruston, Nov 23 '13 at 20:53

score 1 · Answer 1 · edited Apr 13 '17 at 12:34

Adapting this answer, here is a way to use the same XeTeX extensions to put in background colours. I've only done "a" and "e" but it could obviously be extended.

\documentclass{article}
\usepackage{xcolor}
\begin{document}

\XeTeXinterchartokenstate = 1
\newXeTeXintercharclass \tta \XeTeXcharclass `\a \tta
\newXeTeXintercharclass \tte \XeTeXcharclass `\e \tte
%
\setbox2=\hbox{a}
\XeTeXinterchartoks    0 \tta = {\rlap{\textcolor{green}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks \tta \tta = {\rlap{\textcolor{green}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks \tte \tta = {\rlap{\textcolor{green}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks  255 \tta = {\rlap{\textcolor{green}{\vrule height \ht2 width \wd2 depth \dp2}}}
\setbox2=\hbox{e}
\XeTeXinterchartoks    0 \tte = {\rlap{\textcolor{orange}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks \tta \tte = {\rlap{\textcolor{orange}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks \tte \tte = {\rlap{\textcolor{orange}{\vrule height \ht2 width \wd2 depth \dp2}}}
\XeTeXinterchartoks  255 \tte = {\rlap{\textcolor{orange}{\vrule height \ht2 width \wd2 depth \dp2}}}

The awful weary green fox jumped over the lazy dog.

\end{document}

enter image description here

Read the XeTeX reference for details of what \XeTeXinterchartoks does.

Note that the word boundary class currently has the number 4095 (since 2016) instead of 255. — Marijn, Mar 10 '23 at 22:07

score 1 · Answer 2 · edited Apr 13 '17 at 12:35

Combining the answers to two questions yields a simple solution:

Leo Liu's answer to: - soul: broken highlighting with xcolor when using \selectcolormodel

and egreg's answer to: - Color all vowels differently in a LaTeX document

\documentclass{article}
\usepackage{xparse,xcolor}
\usepackage[normalem]{ulem} % use normalem to protect \emph
\newcommand\hl[1]{\bgroup\markoverwith
  {\textcolor{#1}{\rule[-.5ex]{2pt}{2.5ex}}}\ULon}
  \ExplSyntaxOn
\NewDocumentCommand{\colorize}{mm}
 {
  \cs_set:cpn { maryjane_color_#1: } { \hl{#2}{#1} }
 }
\tl_new:N \l_maryjane_text_tl
\NewDocumentCommand{\changecolors}{ O{aeiou} m }
 {
  \tl_set:Nn \l_maryjane_text_tl { #2 }
  \tl_map_inline:nn { #1 } 
   {
    \tl_replace_all:Nnn \l_maryjane_text_tl { ##1 } { \use:c { maryjane_color_##1: } }
   }
  \l_maryjane_text_tl
 }
\ExplSyntaxOff

\colorize{a}{red}
\colorize{e}{blue}
\colorize{i}{green}
\colorize{o}{yellow}
\colorize{u}{brown!30}

\begin{document}

\changecolors{The quick brown fox jumped over the lazy dog}

\changecolors[a]{The quick brown fox jumped over the lazy dog}

\end{document}

output of code

highlighting vowels using a background color

2 Answers2

Linked