\documentclass[10pt,a4paper]{article}
\usepackage{hologo} % used for LuaTeX, PdfTeX and PdfLaTeX logos
\usepackage{graphicx}
\usepackage{textcomp}
\usepackage{url}
\title{pdflatexpicscale}
\author{Peter Willadt\footnote{willadt at t-online.de}}
\date{2018-02-12} %version #version
\begin{document}
\maketitle

\begin{abstract}
  \noindent pdflatexpicscale is software that scales bitmap images to be
  included into Pdf\LaTeX\ documents down to a size sufficient for printing.
  This document describes installation and usage.
\end{abstract}

\tableofcontents

\section{Introduction}

Picture size matters. Digital cameras produce unnecessary large images, this
leads to excessive download times and wasted processing power in the print
driver, for example. Tuning images by hand is fine, but it costs lots of time
and there may be situations where you need e.g. low-res pictures for the web
and high-res pictures for print. When there are requirements that force the
size of images in our document to change, the fun will probably be gone.

There is a freely accessible article\label{tugboatart} in TUGboat (\url{%
https://www.tug.org/TUGboat/tb37-3/tb117willadt.pdf}) accompanying
this package.


\subsection{Similiar Work/Prior Art}

There have been prior attempts to do similiar things. I found
\texttt{degrade.sty}\footnote{see
  \url{http://mirror.ctan.org/graphics/degrade}} 
 and an equivalent con\TeX t module, there are at least two threads on
 stackexchange\footnote{see
   \texttt{http://tex.stackexchange.com/questions/14429/\\
pdftex-reduce-pdf-size-reduce-image-quality}
and 
\texttt{http://tex.stackexchange.com/\\questions/2198/how-to-create-small-pdf-files-for-the-internet}}
 and there had been, as
I have learned, some work by Axel Berger and others, posted 2011-03-31 on
\texttt{de.comp.text.tex}. 

But what motivated me most to find something better than scaling pictures
individually was seeing that Adobe InDesign\textregistered\ does
scale graphics according to the output intent.

\section{Installation}

\subsection{Prerequisites}

You have to install ImageMagick and Perl. If you are using Linux, please use
the tools of your distribution, if they are not already installed. As a
windows user, you may probably use the official ImageMagick distribution at
\url{http://www.imagemagick.org/script/download.php}. For Perl, you got more
options. I have tested pdflatexpicscale with ActiveState ActivePerl, but other
distributions should work too.

You also need the following Perl modules:  \texttt{File::Basename}, 
\texttt{File::Spec}, \texttt{File::Copy}, and \texttt{Getopt::Long}. There are
several ways to get these modules, if you have not got them already:

\begin{itemize}
\item use your Linux distribution's software manager
\item use the Perl CPAN module
\item use ActiveState's \texttt{ppm} software, if you use ActivePerl.
\end{itemize}

Detailled description of these procedures is beyond the scope of this
document. 

There are no special requirements for the versions of the software to install,
but it may be wise to use recent versions, as there have been security flaws
with ImageMagick. 

\subsection{Installation}

If the prerequisites have been fulfilled (which is perhaps standard for a
Linux computer), it is sufficient to move the file
\texttt{pdflatexpicscale.pl} to a place that is included in your PATH and to
make it executable. Of course, there are alternatives. You may perhaps
prefer to type\\
\texttt{perl /path/to/pdflatexpicscale.pl myarticle}\\
instead.

\section{Basic usage}

\subsection{Preparing your \LaTeX\ file, Part~1}

I will assume that you use the graphicx package to include images. The most
important point is \emph{not} to give path names when you use
\verb|\includegraphics|. You do not have to keep all graphics in the current
directory, as the graphicx package comes with the
\verb|\graphicspath| directive.

So, if you have all images in the directory where your \LaTeX\ file resides,
you are done with this. If not, you should undertake the following steps: 

\begin{enumerate}
\item List every path to images within the \verb|\graphicspath| directive.
\item Remove the paths from the \verb|\includegraphics| commands.
\end{enumerate}

Here is an example: If your \LaTeX\ file looks like this:

\begin{verbatim}
Some text...
\includegraphics[size=2in]{/home/fred/photo1} 
Some other text...
\includegraphics[size=1in]{/srv/www/htdocs/logo} 
\end{verbatim}

then you should edit it to the following:

\begin{verbatim}
\graphicspath{{/home/fred/}{/srv/www/htdocs/}}
Some text...
\includegraphics[size=2in]{photo1} 
Some other text...
\includegraphics[size=1in]{logo} 
\end{verbatim}

You hopefully do not have distinct pictures with the same name in the listed
folders. With \verb|\graphicspath| you have to use double braces, even if you
use only one directory. 

\subsection{Preparing your \LaTeX\ file, Part~2}

As size and resolution of images will change, you should specify the display
size of your images by means that are independent of the image, e.g. by using 
something like\\
\verb|\includegraphics[width=.3\textwidth]{...}|\\
or\\
\verb|\includegraphics[width=2cm]{...}|  

\subsection{A complete example}

The workflow looks like this:

\begin{itemize}
\item Edit your file.
\item Run Pdf\LaTeX\ on your file.
\item Create a directory for your scaled pictures.
\item Run pdflatexpicscale on your file.
\item Change the \verb|\graphicspath| directive in your file to use the
  downscaled images.
\item Run Pdf\LaTeX\ on your file.
\end{itemize}

Let us assume that your \LaTeX\ document is called \texttt{myarticle.tex},
that all images reside in the project directory and that you have done the
preparation steps described above. Let us further assume that you want to
produce a PDF file suitable for preview with 72~dpi image resolution.

So you create a subdirectory called \texttt{previewpix} and run Pdf\LaTeX\
like usual on \texttt{myarticle}. Then you issue\\
\texttt{pdflatexpicscale --printdpi=72 --destdir=previewpix myarticle}

If you are curious, you may insert \texttt{--verbose} anywhere before your
project name (and before running it). Then you fire up your editor and add the
following line near the beginning of your \LaTeX\ file:

\verb|\graphicspath{{previewpix/}}|

You may probably check the size of \texttt{myarticle.pdf}.  Then run Pdf\LaTeX\
again on \texttt{myarticle}. I have told you to use double braces with
\verb|\graphicspath|, haven't I?  If you still are curious, you can again
check the size of \texttt{myarticle.pdf}.

When it gets to preparing a print version, you create a directory for images
with more detail, say \texttt{printpix}. You reset the  \verb|\graphicspath|,
run Pdf\LaTeX, issue\\
\texttt{pdflatexpicscale --printdpi=300 --destdir=printpix myarticle}\\
and set \verb|\graphicspath{{printpix/}}| before the next Pdf\LaTeX\ run.

\section{Advanced usage}


\subsection{Excluding files from scaling}

You will probably exclude files from scaling when you think that scaling will
do damage. You may achieve this by several means. Before you ask. Enumerating
files to exclude is not really cool, so this is not supported.

\begin{enumerate}
\item Use \verb|\includegraphics| for this files with full path names. This is
  uncool, but can be done.
\item Pack these files into a special source directory. Read the following
  explanation. 
\end{enumerate}

It works like this: you create three directories for pictures:

\begin{itemize}
\item One for images to stay unscaled. Let's call it \texttt{hires}
\item One for images to scale. Let's call it \texttt{images}
\item One for downscaled images. Let's call it \texttt{printimg}
\end{itemize}

Then you use the feature of \verb|\graphicspath| to include several
directories. Before the first \LaTeX\ run, you say\\
\verb|\graphicspath{{hires/}{images/}}|
and after pdflatexpicscale is through, you change it to\\
\verb|\graphicspath{{hires/}{printimg/}}|

\subsection{Gory details}

pdflatexpicscale reads the log file, not the \LaTeX\ source. So you have to
run Pdf\LaTeX\ at least once before something can happen.

Pure black-and-white images will be treated different from other picture
files: They get four times the resolution, as probably every pixel counts. 
Images that are only a little larger than ideal will not get scaled, but you
may change this from the command line.
If an image will not be scaled, it will be just copied to the destination
directory. 

pdflatexpicscale looks only for the width of images, so if you intend do do
anisotropic scaling you will not get best results. 

Clipping will not work with pdflatexpicscale. The \emph{graphicx} package
devises picture size from the picture file, then applies clipping to it and
afterwards does scaling, rotation and so on. As pdflatexpicscale changes
pictures (as well dimensions as nominal resolution), clipping results will
change too, you will end up with a mess. The same thing happens when you do
not give the figure dimensions in units relying only on document properties
(like page width). 

\subsection{Command line options}

All command line options have to be prepended by two minus signs. If they take
arguments, you should add an equal sign and the argument to your option. All
command line options are optional, but you have to specify a project name.

\paragraph{destdir} followed by \emph{a directory name relative to the current
directory} specifies where the scaled pictures should go. The default is
\texttt{printimg}. The directory has to exist, pdflatexpicscale will not
create directories.

\paragraph{printdpi} followed by the resolution in dpi lets you change the
target resolution. Default is 300, for online use you may supply 96, e.g.

\paragraph{srcdir} followed by \emph{the directory where your unscaled
  pictures are} is normally not required, as pdflatexpicscale gets the path
names from the log file it reads. You may set this option if you have already
changed the \verb|\graphicspath| and are too lazy to change it again. The
default is empty.

\paragraph{tolerance} followed by a number lets you change the range in which
pictures remain unscaled because they are near the target resolution. Default
is 20, that means 20~percent. If target resolution is 300~dpi, files up to
320~dpi get accepted too. Change to 0 if you want no tolerance.

\paragraph{verbose} entertains you by showing what the program is about to
do. 

\paragraph{version} shows the software version.

Calling pdflatexpicscale without any options and without a project name will
display a short usage text.

\subsection{Printer testing}

You can---and you should---actually print a file with images scaled to
distinct resolutions and compare the results. If paper quality matters for you
(inkjet user?), you should repeat this with different paper.

If you belong to the once-privileged class of people who own a PostScript
printer, you may copy the file testprinter.ps to your printer. For all other
folks, this file is useless. Software like Ghostscript will convert the
rasters to uniform colored areas. Anyway, here is what you should see:

\begin{itemize}
\item The uppermost part of the page will present squares filled with
  lines. With my printer, 100~lpi is the best I can get.

\item The middle part of the page shows squares with five levels of gray with
  dotted raster. The result should be similiar.

\item The bottom of the page is dedicated to the ends of the gray scale. Can
  you distinguish 94\% gray from white? Or 6\% gray from black?

\end{itemize}

\section{License}

pdflatexpicscale.pl and the accompanying files are subject to the current
version of the \LaTeX\ project public license.

\section{Bugs, Improvements, and Changes}

Please submit bug reports to the package author (me). I will be glad to make
the package better.\label{bugs}

The file version dates of all the files in this package shall be kept
consistent, even if only one of the files changes. pdflatexpicscale.pl,
however, has also a version number. This number will only be changed when
there are functional changes to pdflatexpicscale.pl. 

\subsection{Changelog}

\paragraph{2016-07-28} Upload of first public version to CTAN.

\paragraph{2016-07-31} Reformatted \emph{Gory details} section and added
information about anisotropic scaling and clipping

\paragraph{2016-08-02} Fixed some typos. Corrected handling of lines wrapped
in the log file. 

\paragraph{2016-10-20} Removed a nagging error message when the program was
called without arguments. Added the argument \texttt{--help}, both due to
suggestions by Karl Berry (thanks a lot).

\paragraph{2016-12-12} Section on similiar work and prior art added (on request).

\paragraph{2017-01-22} Added url of TUGboat article.

\paragraph{2017-01-23} Fixed inconsistent version numbers and changed the url
of degrade.sty on recommendation of CTAN board. Added text on versioning at
the beginning of section~\ref{bugs}. Thanks a lot to the always quick action
and helpful and polite hints.

\paragraph{2017-02-01} With very long pathnames in the log file,
pdflatexpicscale did not find pictures. This is fixed, hopefully.

\paragraph{2018-02-12} Only changes to this document, not to the software: In
this document, the option \texttt{tolerance} had been listed as
\texttt{printdpi}. From now on, this is corrected.

As the TUGboat article corresponding to pdflatexpicscale is freely available
now, the link on page~\pageref{tugboatart} has been adjusted.

% for file version please see line 8
\end{document}