Automatic "Zoom in" hypertext boxes in PDF
The following code (for use with pdfLaTeX) defines the command \zoombox[box line width]{contents}. It creates a click-to-zoom box for fitting the second argument 'contents' into the AdobeReader window. A dotted line is drawn around the box if the optional 'box line width' is >0.
EDIT: The code has been optimized for presentation PDFs (such as beamer generated ones) looked at in full screen mode. The zoom-to box is now centred on the screen when clicked, as requested by @alfC.
\documentclass{beamer}
\usepackage{graphicx}
\usepackage{mwe}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% \zoombox[box line width]{contents}
%
% optimized version for beamer: in full screen, zoom boxes are centred
% in the viewer; useable with any documenclass
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\newsavebox\zb@x
\newcounter{z@@m}
\usepackage{calc}
\newdimen\B@r\newdimen\P@r
\newdimen\@zw\newdimen\@zh\newdimen\@zd
\newcommand{\zoombox}[2][0]{%
\leavevmode%
\sbox\zb@x{#2}%
\setlength\B@r{1pt*\ratio{\wd\zb@x}{\ht\zb@x+\dp\zb@x}}%
\setlength\P@r{1pt*\ratio{\paperwidth}{\paperheight}}%
\ifdim\B@r>\P@r\relax%
\setlength\@zw{\wd\zb@x}\setlength\@zh{\@zw*\ratio{\paperheight}{\paperwidth}}%
\setlength\@zd{(\@zh-\ht\zb@x-\dp\zb@x)*\real{0.5}+\dp\zb@x}%
\setlength\@zh{\@zh-\@zd}%
\else%
\setlength\@zh{\ht\zb@x+\dp\zb@x}%
\setlength\@zw{\@zh*\ratio{\paperwidth}{\paperheight}}%
\setlength\@zh{\ht\zb@x}\setlength\@zd{\dp\zb@x}%
\fi%
\makebox[0pt][l]{\makebox[\wd\zb@x][c]{\makebox[\@zw][l]{%
\pdfdest name {zbfs\thez@@m} fitr
width \@zw\space
height \@zh\space
depth \@zd\space
}}}%
\pdfdest name {zb\thez@@m} fitr
width \wd\zb@x\space
height \ht\zb@x\space
depth \dp\zb@x\space
\immediate\pdfannot
width \wd\zb@x\space
height \ht\zb@x\space
depth \dp\zb@x\space
{%
/Subtype/Link/H/N
/Border [0 0 #1 [1 2]]
/A <<
/S/JavaScript
/JS (
if(typeof(zoomed)=='undefined'||!zoomed){
var lastView=this.viewState;
if(app.fs.isFullScreen) this.gotoNamedDest('zbfs\thez@@m');
else this.gotoNamedDest('zb\thez@@m');
zoomed=true;
}else{
this.viewState=lastView;
zoomed=false;
}
)
>>
}%
\usebox{\zb@x}%
\stepcounter{z@@m}%
}
\makeatother
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\begin{frame}
\zoombox{\includegraphics[width=1cm]{example-image-a}}
\zoombox{\includegraphics[width=1cm]{example-image-b}}
\zoombox{\includegraphics[width=1cm]{example-image-c}}
\zoombox{\includegraphics[height=1cm]{example-image-golden}}
\zoombox{\includegraphics[width=1cm]{example-image-golden-upright}}
\end{frame}
\end{document}
The second example defines pairs of commands for marking opposing corners (lower left & upper right .OR. upper left & lower right) of a zoom box, and commands for marking text sequences/entire paragraphs.
\documentclass{article}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\InputIfFileExists{\jobname.zom}{}{}
\newwrite\zoomdat
\immediate\openout\zoomdat=\jobname.zom
\newcommand{\startzoombox}[2][0]{%
\leavevmode%
\pdfsavepos%
\protected@write\zoomdat{}{%
\string\expandafter\string\def\string\csname\space zb#2.ulx\string\endcsname{%
\noexpand\number\pdflastxpos}%
\string\expandafter\string\def\string\csname\space zb#2.uly\string\endcsname{%
\noexpand\number\pdflastypos}%
}%
\ifcsname zb#2.ulx\endcsname\ifcsname zb#2.lrx\endcsname%
\edef\zoomwd{\dimexpr \csname zb#2.lrx\endcsname sp- \csname zb#2.ulx\endcsname sp\relax}%
\edef\zoomdp{\dimexpr \csname zb#2.uly\endcsname sp- \csname zb#2.lry\endcsname sp\relax}%
\pdfdest name {zb#2.in} fitr
width \zoomwd
height 0pt
depth \zoomdp
\immediate\pdfannot
width \zoomwd
height 0pt
depth \zoomdp
{%
/Subtype/Link/H/N
/Border [0 0 1 [1 2]]
/A <<
/S/JavaScript
/JS (
if(typeof(zoomed)=='undefined'||!zoomed){
var lastView=this.viewState;
zoomed=true;
this.gotoNamedDest('zb#2.in');
}else{
this.viewState=lastView;
zoomed=false;
}
)
>>
}%
\fi\fi%
}
\def\stopzoombox#1{%\leavevmode%
\leavevmode%
\pdfsavepos%
\protected@write\zoomdat{}{%
\string\expandafter\string\def\string\csname\space zb#1.lrx\string\endcsname{%
\noexpand\number\pdflastxpos}%
\string\expandafter\string\def\string\csname\space zb#1.lry\string\endcsname{%
\noexpand\number\pdflastypos}%
}%
}
\def\startzoom{%
\stepcounter{@zb@id}%
\xdef\@lblStack{\the@zb@id.\@lblStack}%
\@ifstar\@startzoomstar\@startzoom%
}
\newcommand{\@startzoom}[1][0]{%
\raisebox{\baselineskip}[0pt][0pt]{\startzoombox[#1]{.\the@zb@id}}%
}
\newcommand{\@startzoomstar}[1][0]{%
\makebox[0pt][r]{\raisebox{\baselineskip}[0pt][0pt]{\startzoombox[#1]{.\the@zb@id}}%
\hspace{\parindent}}%
}
\def\stopzoom{%
\@ifstar\@stopzoomstar\@stopzoom%
}
\def\@stopzoom{%
\@popStack\@lblStack%
\raisebox{-1ex}[0pt][0pt]{\stopzoombox{.\@lblCur}}%
\xspace%
}
\def\@stopzoomstar{%
\@popStack\@lblStack%
\hfill\raisebox{-1ex}[0pt][0pt]{\stopzoombox{.\@lblCur}}%
\xspace%
}
\newcounter{@zb@id}
\def\@lblStack{}
\def\@popStack#1{\expandafter\@@popStack#1\nil}
\def\@@popStack#1.#2\nil{\gdef\@lblCur{#1}\gdef\@lblStack{#2}}
\RequirePackage{xspace}
\makeatother
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\section{Paragraph zooming}
\startzoom[1]First paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first \startzoom[1]\emph{Do not miss this one.}\stopzoom First paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph first paragraph.\stopzoom*
\startzoom*[1]Second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph second paragraph.\stopzoom*
\end{document}
The two commands for marking the corners of a zoom area are
\startzoombox[line width]{label}
and
\stopzoombox{label}
They are meant to be used in picture-making environments, such as pspicture or tikzpicture. Associated command pairs must be identified by unique labels.
For marking text and paragraphs the following commands have been provided:
\startzoom[lwidth]
\startzoom*[lwidth]
\stopzoom
\stopzoom*
The starred versions insert horizontal space (negative \parindent on first line, \hfill at the end of the paragraph).
Zoom areas may be nested. However, smaller ones should be placed on top of bigger ones (i.e. to appear later in the code), in order not to be obscured.
Note that at least two pdflatex runs are necessary.
EDIT:
A dvipdfmx/XeLaTeX version of the \zoombox macro is given in: How do I include a click-to-zoom thumbnail picture in a non-beamer document?
AFAIK there is no predefined macro or package which does all of that, but the elements you need exist:
You can place hyperlinks with zoom windows using the hyperref package. You can get the coordinates required using the zref package(s), especially zref-abspos. These packages are from the same author and play nicely together.
You would need to place the paragraph in its own box.
Place a zref marker before and after the paragraph on the left and right site, respectively to get the coordinates of it. Then put the whole box into a \href macro which uses the coordinates as target. See the manual of hyperref for more details especially \href and the FitR (rectangle zoom).
I suspect you're thinking of the PDF "article thread" feature. This is particularly useful for things like newspapers, where the flow of the text is complicated (multiple columns and the page divided into several articles, and even things like "(continued on page 3)". With Adobe reader, when you mouse over the thread, the hand icon changes to a hand-with-arrow, and upon clicking you zoom to the width of the article, and each additional click follows the flow of the article, no matter how nonlinear and complicated that may be.
PDFtex does have the primitives to support article threads: \pdfthread, \pdfstartthread, \pdfendthread, \pdfthreadmargin. But as far as I know the only latex support is rather limited, via the pdfpages, so only useful if you are using pdfpages for some complex imposition.