Getting calculated value of colour in xcolor - TeX

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Top Answer

4 years ago Joseph Wright

Using l3color one can get this data directly. At present, the colours are independent of those from xcolor, so will have to be defined

\documentclass{article}
\ExplSyntaxOn
\color_set:nnn { mycol } { HTML } {123456}
\ExplSyntaxOff
\begin{document}
\ExplSyntaxOn
\color_export:nnN { mycol!40 }  { HTML } \l_tmpa_tl
\tl_show:N \l_tmpa_tl

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\documentclass{article}\ExplSyntaxOn\color_set:nnn { mycol } { HTML } {123456}\ExplSyntaxOff\begin{document}\ExplSyntaxOn\color_export:nnN { mycol!40 }  { HTML } \l_tmpa_tl\tl_show:N \l_tmpa_tl

which will show the colour in the .log: you could just \tl_use:N \l_tmpa_tl if you want to print.

Answer #2

4 years ago samcarter

You could calculate it manually. An html colour follows the structure #RRGGBB (in base 16) and colour mixing is normally a linear interpolation. So in your case, your colour has a red value of 12₁₆ (= 18₁₀), a green value of 34₁₆ (= 52₁₀) and a blue value of 56₁₆ (= 86₁₀). Thus the colour components after mixing are:

r: 0.4 × 18 + 0.6 × 255 = 160.2 ≈ A0₁₆
g: 0.4 × 52 + 0.6 × 255 = 173.8 ≈ AE₁₆
b: 0.4 × 86 + 0.6 × 255 = 187.4 ≈ BB₁₆

Or you could ask xcolor to show you the key:

\documentclass{article}

\usepackage[landscape]{geometry}

\usepackage{xcolor}

\definecolor{mycolor}{HTML}{123456}

\begin{document}

\textcolor{mycolor}{\rule{3cm}{3cm}}
\textcolor{mycolor!40}{\rule{3cm}{3cm}}

\begin{testcolors}[HTML,rgb,RGB,cmyk,hsb]
\testcolor{mycolor}
\testcolor{mycolor!40}
\end{testcolors}

\end{document}

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\documentclass{article}​\usepackage[landscape]{geometry}​\usepackage{xcolor}​\definecolor{mycolor}{HTML}{123456}​\begin{document}​\textcolor{mycolor}{\rule{3cm}{3cm}}\textcolor{mycolor!40}{\rule{3cm}{3cm}}​\begin{testcolors}[HTML,rgb,RGB,cmyk,hsb]\testcolor{mycolor}\testcolor{mycolor!40}\end{testcolors}​\end{document}
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Answer #3

4 years ago frougon

In order to obtain the hexadecimal notation in a way that is accessible to your code (for further processing, possibly involving computations), you can use xcolor's \extractcolorspecs macro:

\documentclass{article}
\usepackage[T1]{fontenc} % for nice printing of \meaning (only for non-Unicode engines)
\usepackage{xcolor}
\definecolor{mycol}{HTML}{123456}

\ExplSyntaxOn
\cs_new:Npn \__joulev_rgb_spec_to_hex_code_aux:n #1
  {
    \int_to_Hex:n { \fp_eval:n { round(255*(#1)) } }
  }

\cs_new:Npn \joulev_rgb_spec_to_hex_code:n #1
  {
    \clist_map_function:nN {#1} \__joulev_rgb_spec_to_hex_code_aux:n
  }

\cs_generate_variant:Nn \joulev_rgb_spec_to_hex_code:n { V }

\msg_new:nnn { joulev } { not-rgb-color-model }
  { Color~model~for~color~'#1'~isn't~'rgb'. }

\str_new:N \l__joulev_color_model_str

% #1: macro where to store the raw color spec (raw = not converted to hex)
% #2: an rgb-based ⟨color⟩
\cs_new_protected:Npn \__joulev_set_to_raw_color_spec:Nn #1#2
  {
    \extractcolorspecs {#2} \l__joulev_color_model_str #1
    \str_if_eq:VnF \l__joulev_color_model_str { rgb }
      { \msg_error:nnn { joulev } { not-rgb-color-model } {#2} }
  }

% #1: macro where to store the color spec in hexadecimal notation
% #2: an rgb-based ⟨color⟩
\NewDocumentCommand \setToHexColorSpec { m m }
  {
    \__joulev_set_to_raw_color_spec:Nn \l_tmpa_tl {#2}
    \tl_set:Nx #1 { \joulev_rgb_spec_to_hex_code:V \l_tmpa_tl }
  }

\NewDocumentCommand \printHTMLcolorSpec { m }
  {
    \mode_leave_vertical:
    \__joulev_set_to_raw_color_spec:Nn \l_tmpa_tl {#1}
    \hbox:n { \# \joulev_rgb_spec_to_hex_code:V \l_tmpa_tl }
  }
\ExplSyntaxOff

\begin{document}

\extractcolorspecs{mycol!40}{\myModel}{\myColorSpec}
\verb|mycol!40| has model \texttt{\myModel} and spec \texttt{\myColorSpec}.

HTML notation: \printHTMLcolorSpec{mycol!40}

\setToHexColorSpec{\mymacro}{mycol!40}
\meaning\mymacro

\end{document}

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\documentclass{article}\usepackage[T1]{fontenc} % for nice printing of \meaning (only for non-Unicode engines)\usepackage{xcolor}\definecolor{mycol}{HTML}{123456}​\ExplSyntaxOn\cs_new:Npn \__joulev_rgb_spec_to_hex_code_aux:n #1  {    \int_to_Hex:n { \fp_eval:n { round(255*(#1)) } }  }​\cs_new:Npn \joulev_rgb_spec_to_hex_code:n #1  {    \clist_map_function:nN {#1} \__joulev_rgb_spec_to_hex_code_aux:n  }​\cs_generate_variant:Nn \joulev_rgb_spec_to_hex_code:n { V }​\msg_new:nnn { joulev } { not-rgb-color-model }  { Color~model~for~color~'#1'~isn't~'rgb'. }​\str_new:N \l__joulev_color_model_str​% #1: macro where to store the raw color spec (raw = not converted to hex)% #2: an rgb-based ⟨color⟩\cs_new_protected:Npn \__joulev_set_to_raw_color_spec:Nn #1#2  {    \extractcolorspecs {#2} \l__joulev_color_model_str #1    \str_if_eq:VnF \l__joulev_color_model_str { rgb }      { \msg_error:nnn { joulev } { not-rgb-color-model } {#2} }  }​% #1: macro where to store the color spec in hexadecimal notation% #2: an rgb-based ⟨color⟩\NewDocumentCommand \setToHexColorSpec { m m }  {    \__joulev_set_to_raw_color_spec:Nn \l_tmpa_tl {#2}    \tl_set:Nx #1 { \joulev_rgb_spec_to_hex_code:V \l_tmpa_tl }  }​\NewDocumentCommand \printHTMLcolorSpec { m }  {    \mode_leave_vertical:    \__joulev_set_to_raw_color_spec:Nn \l_tmpa_tl {#1}    \hbox:n { \# \joulev_rgb_spec_to_hex_code:V \l_tmpa_tl }  }\ExplSyntaxOff​\begin{document}​\extractcolorspecs{mycol!40}{\myModel}{\myColorSpec}\verb|mycol!40| has model \texttt{\myModel} and spec \texttt{\myColorSpec}.​HTML notation: \printHTMLcolorSpec{mycol!40}​\setToHexColorSpec{\mymacro}{mycol!40}\meaning\mymacro​\end{document}
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3 Answers