Graphics and media/Collections of tips and tricks/Apply shading to text

MetaPost provides shading functions making it easy to fill a path with linear or circular shading. In this simple example, we show how they can be used in conjunction with the outlinetext function and && path combination operator to fill text or equations with a color gradient.

• \setupbodyfont[32pt]
  
  \definecolor[Colour1][h=FF0000]
  \definecolor[Colour2][h=880088]
  \definecolor[Colour3][h=0000FF]
  
  \define[1]\ShadedText%
      {%
      \startuseMPgraphic{shade_text}
          picture ot ;
          ot := outlinetext("#1") ;       % Get the outpline of each cymbol
          path p ;                        % Define a new path
          p := (0,0) -- (0,0);
          for i within ot :               % Loop over the symbol outlines
              p := p && pathpart i ;      % Combine p with the new outline
          endfor
          fill p && cycle                 % Fill the path p...
              withshademethod "linear"    % ... with a linear shading...
              withshadedirection (1.,0.)
              withshadestep (             % ... going from Colour1 to Colour2...
                  withshadefraction .5
                  withshadecolors (\MPcolor{Colour1}, \MPcolor{Colour2})
              )
              withshadestep (
                  withshadefraction 1     % ... then from Colour2 to Colour3
                  withshadecolors (\MPcolor{Colour2}, \MPcolor{Colour3})
              ) ;
      \stopuseMPgraphic
      \useMPgraphic{shade_text}{}%
      }
  
  \starttext
  \startTEXpage
      \ShadedText{test}
      \blank[1em]
      \ShadedText{\dm{\sum_{n=0}^{\infty} 2^{-n} = 2}}
  \stopTEXpage
  \stoptext
  

• 

A slightly simpler approach is to use lmt_outline:

• 
  \setupbodyfont[32pt]
  
  \definecolor[Colour1][h=FF0000]
  \definecolor[Colour2][h=880088]
  \definecolor[Colour3][h=0000FF]
  
  \define[1]\ShadedText{%
    \startuseMPgraphic{shade_text}
      draw lmt_outline [
          kind = "outline",
          text = "#1",
      ]
        withshademethod "linear"
        withshadedirection (1.,0.)
        withshadestep (
            withshadefraction .5
            withshadecolors (\MPcolor{Colour1}, \MPcolor{Colour2})
        )
        withshadestep (
            withshadefraction 1
            withshadecolors (\MPcolor{Colour2}, \MPcolor{Colour3})
        ) ;
    \stopuseMPgraphic
    \useMPgraphic{shade_text}{}%
  }
  
  \starttext
  \startTEXpage
    \ShadedText{test}
    \blank[big]
    \ShadedText{\dm{\sum_{n=0}^{\infty} 2^{-n} = 2}}
  \stopTEXpage
  \stoptext
  

•