4

I'm using tikz to lay out an image on a page and control precisely its (absolute) position.

I now want to attach a caption to this image and align the (bottom) baseline of my caption to the bottom of the picture.

While this is perfectly working if I manually typeset the caption within a tikz node (see MWE page 1), I can't achieve the same result with the \caption macro. Indeed, it seems that the \caption is embedded in a sort of minipage and that I can only align the bottom of the minipage with the bottom of my image.

I would like to keep using the \captionof macro because my page layout is part of a larger document with other floating figures, a list of figures and continuous numbering of figures.

How can I get the proper alignement of the \captionof baseline ?

\documentclass[a4]{article}
\usepackage{graphicx,lipsum}
\usepackage{adjustbox}
\usepackage{tikz}
\usepackage{tikzpagenodes}
\usetikzlibrary{backgrounds,positioning}
\usepackage{subcaption}

\renewcommand{\fboxsep}{0pt}
\setlength{\fboxrule}{0.1pt}
\newlength{\radius}
\setlength{\radius}{0.5mm}


% absolute positioning of a picture on a page
\newcommand{\mypict}{
    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \coordinate[] (P) at (current page.center);
        \node[anchor=center] at (P){
            \includegraphics[width=8cm]{example-image-a}
        };
        \coordinate (TL) at (current bounding box.north west); % top-left corner
        \coordinate (BL) at (current bounding box.south west); % bottom-left corner
        \coordinate (TR) at (current bounding box.north east); % top-left corner
        \coordinate (BR) at (current bounding box.south east); % bottom-left corner
        \coordinate[xshift=5cm] (B) at (current bounding box.south east); % bottom-left corner
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}
    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \filldraw[red] (TL) circle [radius=\radius];
        \filldraw[red] (BL) circle [radius=\radius];
        \filldraw[red] (TR) circle [radius=\radius];
        \filldraw[red] (BR) circle [radius=\radius];
        \draw[line width=0.5pt,red] (BR)--(B);
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}
}


\begin{document}

% FIRST PAGE
% manual caption
\mypict
\begin{tikzpicture}[remember picture, inner sep=0pt]
    \node[anchor=base west] at (BR){%
            \fbox{\parbox[b]{5cm}{\textbf{Figure 2.3~:} This is my first custom caption and the baseline is correctly aligned with the picture gqp.}}
    };
    \pgfresetboundingbox
    \path[use as bounding box] (0,0);
\end{tikzpicture}

% SECOND PAGE
% auto caption with \captionof
\clearpage
\mypict

\captionsetup{skip=0pt, textfont={sf,small}, labelfont={sf,small,bf}}

\begin{tikzpicture}[remember picture, inner sep=0pt]
    \node[anchor=base west] at (BR){%
            \fbox{\parbox[b]{5cm}{\captionof{figure}[list entry]{This is my first custom caption and the baseline is correctly aligned with the picture gqp.}}}
    };
    \pgfresetboundingbox
    \path[use as bounding box] (0,0);
\end{tikzpicture}

\end{document}

\parbox leads to a correct baseline alignement \captionof bounding box is just bottom aligned

  • 1
    Welcome to TeX.SE! This is the most advanced first question I've seen in a while! (But personally I'd say that the caption of the second rather than the first question is correctly aligned.) – user121799 Feb 12 '18 at 23:00
  • a4 won't do anything useful, by the way. – cfr Feb 12 '18 at 23:08
  • @marmot I agree, though it might depend on the content of the actual image, I guess. Although it is hard to think of what might make the first alignment look correct. – cfr Feb 12 '18 at 23:10
  • Well, maybe you are right about which option is better. But if you think about single line captions It might be preferable to get a baseline alignment. It looks weird otherwise. Any idea to achieve this with \captionof ? – Lionel du Peloux Feb 12 '18 at 23:31
  • 1
    You would have to copy/modify \@makecaption from whatever package currently sets it. You might even be able to use tikz commands INSIDE \@makecaption. Also, you would be better off using a named local bounding box from a scope. – John Kormylo Feb 13 '18 at 17:57
1

There is an option in caption package that minimizes the problem. If I pass the strut=off option to the caption style the enclosing box is now tight to the caption text paragraph.

However I still cannot mesure the depth of the box/minipage generated by the captionof command and yshift the box consequently (see page 3 of the MWE).

The solution might be to trigger a "phantom captionof" to get correct label and list entry and to print the caption title separately in a common macro.

\documentclass[a4]{article}
    \usepackage{graphicx,lipsum}
    \usepackage{adjustbox}
    \usepackage{tikz}
    \usepackage{tikzpagenodes}
    \usetikzlibrary{backgrounds,positioning}
    \usepackage{subcaption}

    \renewcommand{\fboxsep}{0pt}
    \setlength{\fboxrule}{0.1pt}
    \newlength{\radius}
    \setlength{\radius}{0.5mm}


    % absolute positioning of a picture on a page
    \newcommand{\mypict}{
        \begin{tikzpicture}[remember picture, inner sep=0pt]
            \coordinate[] (P) at (current page.north);
            \node[anchor=north] at (P){
                \includegraphics[width=8cm]{example-image-a}
            };
            \coordinate (TL) at (current bounding box.north west); % top-left corner
            \coordinate (BL) at (current bounding box.south west); % bottom-left corner
            \coordinate (TR) at (current bounding box.north east); % top-left corner
            \coordinate (BR) at (current bounding box.south east); % bottom-left corner
            \coordinate[xshift=5cm] (B) at (current bounding box.south east); % bottom-left corner
            \pgfresetboundingbox
            \path[use as bounding box] (0,0);
        \end{tikzpicture}
        \begin{tikzpicture}[remember picture, inner sep=0pt]
            \filldraw[red] (TL) circle [radius=\radius];
            \filldraw[red] (BL) circle [radius=\radius];
            \filldraw[red] (TR) circle [radius=\radius];
            \filldraw[red] (BR) circle [radius=\radius];
            \draw[line width=0.5pt,red] (BR)--(B);
            \pgfresetboundingbox
            \path[use as bounding box] (0,0);
        \end{tikzpicture}
    }

    \makeatletter

    \caption@AtBeginDocument{%
        \def\rawcaptionof{\caption@teststar\caption@of{\caption*}\caption}%
    }

    \newcommand*\rawcaption@of[2]{\caption@settype*{#2}#1}

    \long\def\caption@@caption#1[#2]#3{

    \ifcaption@star \else
        \caption@prepareanchor{#1}{#2}%
        \memcaptioninfo{#1}{\csname the#1\endcsname}{#2}{#3}%
        \@nameuse{nag@hascaptiontrue}%
    \fi
    \par
    \caption@beginex{#1}{#2}{#3}%
        % \caption@setfloatcapt{%
        %   \caption@boxrestore
        %   \if@minipage
        %     \@setminipage
        %   \fi
        \caption@normalsize
        \ifcaption@star
            \let\caption@makeanchor\@firstofone
        \fi

        \@makecaption{\csname fnum@#1\endcsname}%
                    {\ignorespaces\caption@makeanchor{#3}}\par
        %   \caption@if@minipage\@minipagetrue\@minipagefalse
        %   }%
    \caption@end}

    \makeatother

    \begin{document}

    % FIRST PAGE
    % manual caption
    \mypict
    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \node[anchor=base west] at (BR){%
                \fbox{\parbox[b]{5cm}{\textbf{Figure 2.3~:} This is my first custom caption and the baseline is correctly aligned with the picture gqp.}}
        };
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}

    % SECOND PAGE
    % auto caption with \captionof
    \clearpage
    \mypict

    \captionsetup{skip=0pt, textfont={sf,small}, labelfont={sf,small,bf}}

    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \node[anchor=base west] at (BR){%
                \fbox{\parbox[b]{5cm}{\rawcaptionof{figure}[list entry]{This is my first custom caption and the baseline is correctly aligned with the picture gqp.}}}
        };
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}


    % THIRD PAGE
    % auto caption with \captionof
    \clearpage
    \mypict

    \captionsetup{skip=0pt, textfont={sf,small}, labelfont={sf,small,bf},strut=off}


    \newsavebox{\mybox}
    \savebox{\mybox}{\parbox[b]{5cm}{\rawcaptionof{figure}[list entry]{This is my first custom caption and the baseline is correctly aligned with the picture gqp.}}}

    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \node[anchor=base west,yshift=-\ht\mybox] at (BR){%
                \fbox{\usebox{\mybox}}
        };
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}

    \begin{tikzpicture}[remember picture, inner sep=0pt]
        \node[anchor=base east,yshift=-\dp\mybox] at (BL){%
                \fbox{\usebox{\mybox}}
        };
        \pgfresetboundingbox
        \path[use as bounding box] (0,0);
    \end{tikzpicture}


\end{document} 

enter image description here

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