Rainbow-colored text strings

Question

Is it possible to create the following effect in latex?

The core is that it have a distinct color for each word instead of using a shading, which can mess the text up.

It's fine if this is done using javascript and svg.

Credits for Celeste for this image...... I'm trying to port wavedash.ppt to latex using dvisvgm, but I'm kinda stuck.

Welcome to TSE. What did you try? – José Carlos Santos Nov 21 '23 at 14:21 — José Carlos Santos, Nov 21 '23 at 14:21
Jose, actually I have no idea where to start...... – ygy Nov 21 '23 at 15:20 — ygy, Nov 21 '23 at 15:20

samcarter_is_at_topanswers.xyz · Accepted Answer · 2024-02-21T10:16:55.747

You could use this adaptation of the gradient-text package:

\documentclass{article}
% rainbow text (based on the gradient-text package)
\makeatletter
\ExplSyntaxOn
\clist_new:N\l_gtext_First_clist
\clist_new:N\l_gtext_Last_clist
\int_new:N\l_gtext_MaxIndex_int
\int_new:N\l_gtext_Ratio_int
\newcommand{\gr@dient}[8]{
  \int_set:Nn\l_gtext_MaxIndex_int{\int_eval:n{\str_count:n{#1}}}
  \int_step_inline:nnn{1}{\l_gtext_MaxIndex_int}{
      \exp_args:Ne\str_if_eq:nnTF{\str_item:Nn{#1}{##1}}{~}{}{
        \int_set:Nn\l_gtext_Ratio_int{\int_eval:n{\l_gtext_Ratio_int+1}}
      }
        \color_select:nn{#8}{
          \int_eval:n{(\int_use:N\l_gtext_Ratio_int#5+(\l_gtext_MaxIndex_int-##1)#2)/\l_gtext_MaxIndex_int},
          \int_eval:n{(\int_use:N\l_gtext_Ratio_int#6+(\l_gtext_MaxIndex_int-##1)#3)/\l_gtext_MaxIndex_int},
          \int_eval:n{(\int_use:N\l_gtext_Ratio_int#7+(\l_gtext_MaxIndex_int-##1)#4)/\l_gtext_MaxIndex_int}
      }\str_item:Nn{#1}{##1}
  }
}
\NewDocumentCommand\gradient{mmmm}{{
  \clist_set:Nn\l_gtext_First_clist {#3}
  \clist_set:Nn\l_gtext_Last_clist {#4}
  \gr@dient{#2}
  {\clist_item:Nn\l_gtext_First_clist{1}}
  {\clist_item:Nn\l_gtext_First_clist{2}}
  {\clist_item:Nn\l_gtext_First_clist{3}}
  {\clist_item:Nn\l_gtext_Last_clist{1}}
  {\clist_item:Nn\l_gtext_Last_clist{2}}
  {\clist_item:Nn\l_gtext_Last_clist{3}}
  {#1}
}}
\ExplSyntaxOff
\NewDocumentCommand\gradientRGB{mmm}{
  \gradient{RGB}{#1}{#2}{#3}
}
\NewDocumentCommand\gradientHSB{mmm}{
  \gradient{HSB}{#1}{#2}{#3}
}
\makeatother
\begin{document}
\gradient{HSB}{Colour is all.}{0,240,200}{240,240,200}
\gradient{RGB}{Colour is all.}{255,0,0}{0,0,255}
\gradientHSB{Colour is all.}{0,240,200}{240,240,200}
\gradientRGB{Colour is all.}{255,0,0}{0,0,255}
\end{document}

Wow, this looks amazing. Do you have any resources on the clist and stuff? I really want to know deeper about latex but I don't know where to start. — ygy, Nov 21 '23 at 15:24
@ygy See https://tug.org/TUGboat/tb44-1/tb136peischl-expl3.pdf — samcarter_is_at_topanswers.xyz, Nov 21 '23 at 15:36
@samcarter_is_at_topanswers.xyz Wow, this looks very nice. Is there also a possibility to have a color gradiant from up to down? Thx — mario1000, Nov 22 '23 at 08:08
@mario1000 If your text has enough lines of text, it will automatically create a gradient from top to bottom. — samcarter_is_at_topanswers.xyz, Nov 22 '23 at 08:50
I think your idea is very good. As the original author of the package, may I include your code (with reference) into the next version? — youthdoo, Feb 21 '24 at 10:08
@youthdoo Of course! Please take whatever code you find useful! — samcarter_is_at_topanswers.xyz, Feb 21 '24 at 10:17

score 4 · Answer 2 · answered Nov 22 '23 at 07:11

Here's a TikZ solution adapted from an earlier answer of mine, which might be of interest in relation to Beamer, for example.

\documentclass[border=10pt,multi,tikz]{standalone}
% ateb: https://tex.stackexchange.com/a/701971/
% addaswyd o fy ateb: https://tex.stackexchange.com/a/344548/
\usetikzlibrary{fadings}
\usepackage{xparse}
\pgfdeclarehorizontalshading{rainbow}{100bp}{%
  rgb(0bp)=(1,0,0);
  rgb(26bp)=(1,0,0);
  rgb(33bp)=(1,.5,0);
  rgb(40bp)=(1,1,0);
  rgb(47bp)=(0,1,0);
  rgb(54bp)=(0,1,1);
  rgb(61bp)=(0,0,1);
  rgb(68bp)=(1,0,1);
  rgb(75bp)=(.5,0,.5);
  rgb(100bp)=(.5,0,.5)}
\begin{tikzfadingfrompicture}[name=wavedashing]
  \node [text=transparent!0, inner sep=0pt] {\sffamily\bfseries\selectfont Wavedashing and You};
\end{tikzfadingfrompicture}%
\begin{document}
\begin{tikzpicture}
  \shade [shading=rainbow, path fading=wavedashing, fit fading=false] (-18mm,-10mm) rectangle (18mm,10mm);
\end{tikzpicture}
\end{document}

score 2 · Answer 3 · answered Feb 21 '24 at 14:05

Adapting my fading-black answer here: How can I 'fade out' text after a certain length?, to change color over the full string length:

\documentclass{article}
\usepackage{xcolor,ifthen}
\newcounter{tmpcounter}
\newlength\cumlength
\newlength\critlength
\newlength\tmplength
\newcount\mynum
\newcount\myden
\makeatletter
\newcommand\ColorShift[3]{\colorlet{cfrom}{#1}\colorlet{cto}{#2}\sbox0{#3}%
  \critlength=\wd0\relax\cumlength=0pt\relax%
  \def\cumstring{}\fahelp{\critlength}{#3}}
\newcommand\fahelp[2]{\prefahelper#2 \relax\fahelper#2\relax}
\def\prefahelper#1#2 #3\relax{\gdef\wordremaining{#1#2}}
\def\fahelper#1#2\relax{%
  \global\protected@edef\cumstring{\cumstring#1}%
  \ifthenelse{\equal{#1}{\wordremaining}}{%
    \global\protected@edef\cumstring{\cumstring\ }}{}%
  \setbox0=\hbox{\cumstring}%
  \tmplength=.01\critlength\relax%
  \mynum=\wd0\relax%
  \myden=\tmplength\relax%
  \divide\mynum by\myden%
  \setcounter{tmpcounter}{\numexpr100-\the\mynum}%
  \ifnum\thetmpcounter<0\setcounter{tmpcounter}{0}\fi%
  \textcolor{cfrom!\thetmpcounter!cto}{#1}%
  \ifthenelse{\equal{#1}{\wordremaining}}{\ }{}%
  \ifdim\wd0<\critlength%
    \ifx\relax#2\relax\else\fahelp{\critlength}{#2}\fi%
  \fi%
}
\makeatother
\begin{document}
\bfseries\sffamily
\ColorShift{cyan}{yellow!80!red}{Test}%
\ColorShift{red}{blue}{Testing whether this shifts color}%
\ColorShift{black}{red}{This is a very long multi-line test
This is a very long test This is a very long test
This is a very long test This is a very long test}
\end{document}

Rainbow-colored text strings

3 Answers3