Get key value of command

Question

i'm beginner in Tex and i have tex file

\documentclass{article}

\addtolength{\jot}{1em}

\begin{document}
\begin{verbatim}
\end{verbatim}
\begin{chestnutStem}
In the following figure, if the spinner is divided into 8 colored sections, what is the probability of it stopping at blue?

\centerline{\includepdf[page=2]{mypdf.pdf}}

\end{chestnutStem}

\chestnutKey{
$        \frac{1}{4}      $
}

\begin{chestnutAnswer}

        \begin{align*}
        \textrm{The probability of the spinner stopping at blue}&=\frac{\textrm{the number of blue sections}}{\textrm{total number of sections}}\\
        &=\frac{2}{8}\\
        &=\frac{1}{4}.
        \end{align*}

\end{chestnutAnswer}

\end{document} 

and i have cls file

\ProvidesClass{chestnut}[2016/02/17]
\LoadClass{article}
\RequirePackage{amsmath}
\RequirePackage{kvoptions}
\RequirePackage{graphicx}
\RequirePackage{xkeyval}
\DeclareStringOption{country}{}
\DeclareStringOption{language}{}
\DeclareStringOption{math}{}
\DeclareStringOption{numerals}{}
\ProcessKeyvalOptions*\relax

\DeclareOption{example}{%
\typeout{You are using example object.}

}%

\DeclareOption*{}{}
\ProcessOptions*\relax

\RequirePackage[lmargin=0.5in,rmargin=0.5in,tmargin=0.5in,bmargin=0.5in]{geometry}
\let\country=\chestnut@country
\typeout{ Your country \country}

\let\language=\chestnut@language
\typeout{ Your language \language}

\let\math=\chestnut@math
\typeout{ Your symbols language is \math}

\let\numerals = \chestnut@numerals
\typeout{ Your numerals are in \numerals}

\newenvironment{chestnutStem}{\underline{\textbf{Stem}}\\* }{\hfill \\* }

\newcommand\chestnutKey[1]{\underline{\textbf{Key}}\\*#1\hfill\\* }

\newenvironment{chestnutAnswer}{\underline{\textbf{Answer}}\\*}{\hfill \\* }

\RequirePackage{alternative4ht}
\altusepackage{pdfpages}
\newcommand\chestnutTikZ[1]{\includepdf[pages=-,width=.9\textwidth]{#1}}

\setlength{\parindent}{0pt}
\pagenumbering{gobble}
\IfFileExists{approved.jpg}{%
\RequirePackage{fancyhdr}
\renewcommand\headrule{}
\rhead{\vspace{0.5in}\includegraphics[scale=0.2]{approved.png}}
\pagestyle{fancy}
}%

and alternative4ht.sty file

\ProvidesPackage{alternative4ht}

\newcommand{\altusepackage}[2][]{%
    \ifx\HCode\relax%
    \usepackage[#1]{#2}%
    \else%
    \IfFileExists{#2-alt4ht.sty}{%
      \usepackage[#1]{#2-alt4ht}%
    }{\typeout{alternative4ht: no patch file for #2}}
    \fi%
}
\endinput

and pdfpages-alt4ht.sty file

\ProvidesPackage{pdfpages-alt4ht}
\RequirePackage{graphicx}

\newcommand\includepdf[2][]{%
    \includegraphics{#2}
}

\endinput

and cfg file to convert pdf pages to png images

\Preamble{xhtml}
  \Configure{graphics*}  
         {pdf}  
         {\Needs{"convert -scene 1 \csname Gin@base\endcsname.pdf  
                               \csname Gin@base\endcsname.png"}%  
          \Picture[pict]{\csname Gin@base\endcsname .png}% here i want add page number with pdf file name for example <mypdf-2.png>
          \special{t4ht+@File: \csname Gin@base\endcsname.png}
         }  
\begin{document}
\EndPreamble

I want get [page] value option in \includepdf command to use it in config file

Answer 1

pdfpages is one of packages which causes tex4ht to fail once they are included. In this case, TeX source must be altered, which is something that we try to avoid with tex4ht. helpers4ht bundle provides \altusepackage command, which can be used to load alternative version of packages for tex4ht. These alternative packages are named packagename-alt4ht.sty. They contain definitions for macros used in the document. Definition for pdfpages was only basic, it could be used to include only one paged pdf document.

To support multipage pdf files, I've added pages option to \includepdf command in pdfpages-alt4ht.sty package. It doesn't support all features of original, as it would be quite difficult to implement it and I don't think that it makes sense in HTML output:

\ProvidesPackage{pdfpages-alt4ht}
\RequirePackage{graphicx}
\RequirePackage{xkeyval}
\define@key{includepdf}{pages}{\edef\current@pdf@page{\the\numexpr #1-1\relax}}

\newcommand\includepdf[2][]{%
  \def\current@pdf@page{0}
    \setkeys*{includepdf}{#1}
    \filename@parse{#2}
    \def\current@png@name{\filename@area\filename@base-\current@pdf@page.png}
    \IfFileExists{\current@png@name}{}{%
      \Needs{"convert #2[\current@pdf@page]
      \current@png@name"}
    }
    \includegraphics{\current@png@name}
  }

  \endinput

it saves requested page in \current@pdf@page macro, it must be decremented by 1, because imagemagick counts pages from 0. The png name is constructed as imagename-pagenumber.png and convert program is called only if it doesn't exist yet.

I had to fix one issue in chestnut.cls, there was missing {} in IfFileExists:

\ProvidesClass{chestnut}[2016/02/17]
\LoadClass{article}
\RequirePackage{amsmath}
\RequirePackage{kvoptions}
\RequirePackage{graphicx}
\RequirePackage{xkeyval}
\DeclareStringOption{country}{}
\DeclareStringOption{language}{}
\DeclareStringOption{math}{}
\DeclareStringOption{numerals}{}
\ProcessKeyvalOptions*\relax

\DeclareOption{example}{%
\typeout{You are using example object.}

}%

\DeclareOption*{}{}
\ProcessOptions*\relax

\RequirePackage[lmargin=0.5in,rmargin=0.5in,tmargin=0.5in,bmargin=0.5in]{geometry}
\let\country=\chestnut@country
\typeout{ Your country \country}

\let\language=\chestnut@language
\typeout{ Your language \language}

\let\math=\chestnut@math
\typeout{ Your symbols language is \math}

\let\numerals = \chestnut@numerals
\typeout{ Your numerals are in \numerals}

\newenvironment{chestnutStem}{\underline{\textbf{Stem}}\\* }{\hfill \\* }

\newcommand\chestnutKey[1]{\underline{\textbf{Key}}\\*#1\hfill\\* }

\newenvironment{chestnutAnswer}{\underline{\textbf{Answer}}\\*}{\hfill \\* }

\RequirePackage{alternative4ht}
\altusepackage{pdfpages}
\newcommand\chestnutTikZ[1]{\includepdf[pages=-,width=.9\textwidth]{#1}}

\setlength{\parindent}{0pt}
\pagenumbering{gobble}
\IfFileExists{approved.jpg}{%
\RequirePackage{fancyhdr}
\renewcommand\headrule{}
\rhead{\vspace{0.5in}\includegraphics[scale=0.2]{approved.png}}
\pagestyle{fancy}
}{}%

and also your TeX file, because chestnut class wasn't used:

\documentclass{chestnut}

\addtolength{\jot}{1em}

\begin{document}
\begin{verbatim}
\end{verbatim}
\begin{chestnutStem}
In the following figure, if the spinner is divided into 8 colored sections, what is the probability of it stopping at blue?

\centerline{\includepdf[pages=2]{mypdf.pdf}}

\end{chestnutStem}

\chestnutKey{
$        \frac{1}{4}      $
}

\begin{chestnutAnswer}

        \begin{align*}
        \textrm{The probability of the spinner stopping at blue}&=\frac{\textrm{the number of blue sections}}{\textrm{total number of sections}}\\
        &=\frac{2}{8}\\
        &=\frac{1}{4}.
        \end{align*}

\end{chestnutAnswer}

\end{document} 

sample output: