Extracting commands from environment

Question

In Automatic scaling of tikz images in floatrow I was asking how to scale several images in one row to the same height and to scale the resulting row to linewidth.

I would like to automate the process further and was wondering if it is possible to define an environment as follows (the desired behaviour will be explained below):

\begin{scaleRow}[\linewidth]
  \somecode{\scaledImage{image1code}}
  \othercode
  \somecode{\scaledImage{image2code}}
  ...
  \othercode\maybeDifferent
  \somecode{\scaledImage{image<N>code}}
\end{scaleRow}

The environment should collect all the code inside \scaledImage, so I can use the method given in the answer to the referenced question automatically to calculate the scaleratios for each image.

After running this calculations, I would like to replace \scaledImage{code} with code and every occurence of \scalefactor inside code with the scalefactor I calculated and actually render the code in the environment.

The reason why I want to render the image twice is that I aim to use tikzscale, otherwise I could replace code by the savebox I will need to calculate the width.

Note: I would like to at least try some of the required coding myself to get started with latex coding, however I am a complete novice, while I am sure that most of this is feasible, I am not sure about the extraction of the scaledImage part from the enviornment. I would appreciate a good pointer on that so I can try what I can put together from that point.

What makes the matter slightly more difficult is that I am afraid of side effects. So I think just executing all code twice (once hidden e.g. by putting it in an sbox or somehow throwing its output away) is dangerous, if for instance a counter is modified.

Answer 1

Your specifications are somewhat vague, so I may have taken some liberties in interpreting what you wanted to do.

For those who are not familiar with your earlier question, I should point out here that you requested and I introduced the concept of a "row-figure" which is constructed of various sized subfigures, all of which are to be scaled (with aspect ratio preserved) in such a way as to occupy an overall width specified by the user (default \textwidth).

I have introduced the following commands that work inside an environment:

\rowfigurewidth{specified width of row-figure} - which defaults to \textwidth

\startrowfigure[starting subfig number]{left-most image to store in the new row-figure}

\addrowfigure{figure to store at current right-end of row-figure}

\presentrowfigure - regurgitates the currently constructed row figure

\showrowfigure{}{}{}{} - the macro that formats each subfigure component of the row-figure (not called by user, but determines format of presented row-figure)

rowfigcount is the counter that contains the current value of subfigs employed, if one wishes continue on a subsequent line (via \therowfigcount as optional argument to \startrowfigure.

Sample usage would be:

\begin{figure}[ht]
\startrowfigure{\figa}
\addrowfigure{\figb}
\addrowfigure{\figc}
\addrowfigure{\figd}
\presentrowfigure
\end{figure}

And the whole code is given below:

\documentclass{article}
\usepackage{scalerel}
\usepackage{fp}
\usepackage{stackengine}
\def\stacktype{L}
\usepackage{xcolor}
\newcount\figwidthc
\newcount\textwidthc
\newcounter{rowfigcount}
\newcounter{rowfigindex}
\newsavebox\compositefig
\newlength\rowfigwidth
\def\rowfigwidthstring{\textwidth}
\newcommand\rowfigurewidth[1]{\edef\rowfigwidthstring{#1}}
\newcommand\startrowfigure[2][0]{%
  \sbox\compositefig{#2}%
  \edef\rowfigstart{#1}%
  \setcounter{rowfigcount}{#1}%
  \addtocounter{rowfigcount}{1}%
  \expandafter\def\csname rowfig\roman{rowfigcount}\endcsname{#2}%
}
\newcommand\addrowfigure[1]{%
  \sbox\compositefig{\scalerel{\usebox{\compositefig}}{$#1$}}%
  \addtocounter{rowfigcount}{1}%
  \expandafter\def\csname rowfig\roman{rowfigcount}\endcsname{#1}%
}
\newcommand\presentrowfigure{%
  \figwidthc=\wd\compositefig%
  \setlength{\rowfigwidth}{\rowfigwidthstring}%
  \textwidthc=\rowfigwidth%
  \FPdiv\scaleratio{\the\textwidthc}{\the\figwidthc}%
  \setcounter{rowfigindex}{\rowfigstart}%
  \whiledo{\value{rowfigindex} < \value{rowfigcount}}{%
    \stepcounter{rowfigindex}%
    \showrowfigure%
      {\scaleratio}%
      {\alph{rowfigindex}}%
      {\csname rowfig\roman{rowfigindex}\endcsname}%
      {\csname rowfig\roman{rowfigcount}\endcsname}%
  }
}
\newcommand\showrowfigure[4]{%
  \stackunder{\scalebox{#1}{\scalerel*{$#3$}{$#4$}}}{(#2)}%
}
\begin{document}
\def\figa{\color{blue}\rule{.5in}{.7in}}
\def\figb{\color{red}\rule{.7in}{.3in}}
\def\figc{\color{green}\rule{.4in}{.5in}}
\def\figd{\color{black}\rule{1.in}{.8in}}

\def\fige{\color{red}\rule{1.5in}{.7in}}
\def\figf{\color{cyan}\rule{1.7in}{1.3in}}
\def\figg{\color{magenta}\rule{1.4in}{1.5in}}
\def\figh{\color{black}\rule{1.in}{.8in}}

Here I demonstrate row figures:

\begin{figure}[ht]
\startrowfigure{\figa}
\addrowfigure{\figb}
\addrowfigure{\figc}
\addrowfigure{\figd}
\presentrowfigure
\\
\vspace{1em}\\
\rowfigurewidth{.8\textwidth}
\startrowfigure[\therowfigcount]{\fige}
\addrowfigure{\figf}
\addrowfigure{\figg}
\addrowfigure{\figh}
\presentrowfigure
\caption{These are my row figures}
\end{figure}

which came from these raw images:

\begin{figure}[ht]
\figa\figb\figc\figd
\\
\vspace{1em}\\
\fige\figf\figg\figh
\caption{These are the unaltered images}
\end{figure}
\end{document} 

Obviously, if you wanted to do something more than just put a (subfig number) below the individual images, you would have to pass it to \startrowfig and \addrowfig, store it, and recall it via an entry in \showrowfigure