Vector to raster graphics for draft mode

Question

I'm writing a document which has many plots with quite a lot of data points. Those plots are stored as .pdf vector images and their rendering takes a lot of time. So every time I stumble upon a page with one of those, my editor freezes for a solid minute.

I know that graphicsx has a draft option but that hides the images which is not a very good solution since then I can't tell the images apart just by the filename. Those are results of experimental runs with quite generic names.

Is there perhaps a way to rasterize the images (e.g. into .png) in draft mode and use the original .pdf in final mode? I know that I could use ImageMagick or whatever external tools to do the conversion but that seems like a lot of extra work since I would need to add every image to a makefile and duplicate the \includegraphics for draft and final.

There are some parameters of graphicsx such as type or command which are not explained in the documentation. Could this perhaps be achieved using one of those? Could I perhaps hook the \includegraphics and call an external command? I would manage writing the command but I have no Idea how hooks work in LaTeX.

Otherwise, I'm well aware of the fact that raster graphics are inferior to vector graphics as far as the quality is concerned. I'm going to use vector graphics in the final version. This is intended solely for quick draft preview.

Answer 1

The search path for the images can be changed:

• \graphicspath with a directory for PDF images or it counterparts, the PNG images.
• \DeclareGraphicsExtensions can be used to change the order, which extension is used first, when the image file was given without extension. Package grfext provides an interface for changing the setting.

Package epstopdf can be used to call the conversion from PDF to PNG automatically, if pdfTeX or luaTeX is used and the shell escape feature is enabled.

Example:

If \mydraft is defined to be Y (\let\mydraft=Y), then the rule for the extension .pdf is overwritten to make a conversion to .png via ImageMagick's convert. Otherwise the .pdf extension is preferred.

\documentclass{article}
\usepackage{graphicx}
\usepackage{grfext}

\ifx\mydraft Y
  \usepackage{epstopdf-base}
  \epstopdfDeclareGraphicsRule{.pdf}{png}{.png}{%
    convert #1 \OutputFile
  }  
  \epstopdfDeclareGraphicsRule{.PDF}{png}{.png}{%
    convert #1 \OutputFile
  }  
\else
  \PrependGraphicsExtension*{.pdf}
\fi

\begin{document}
\includegraphics{image}
\end{document}

The special draft mode is enabled by \let\mydraft=Y, which can also be given on the command line, e.g.:

pdflatex --shell-escape "\let\mydraft=Y\input{mydocument}"

Then image.pdf is converted and included as image-pdf-converted-to.png.

Otherwise, image.pdf is included, even if image.png lies around.

Key for \includegraphics

The conversion feature can also be limited to \includegraphics by use of a key pdfpng. The key code changes the graphics rule for .pdf files to convert them to PNG. If \mydraft is not Y, then the key is a no-op.

\documentclass{article}
\usepackage{graphicx}
\usepackage{grfext}

\ifx\mydraft Y
  \usepackage{epstopdf-base}
  \csname define@key\endcsname{Gin}{pdfpng}[]{%
    \epstopdfDeclareGraphicsRule{.pdf}{png}{.png}{%
      convert ##1 \OutputFile
    }%
  }
\else
  \PrependGraphicsExtensions*{.pdf}
  \csname define@key\endcsname{Gin}{pdfpng}[]{}
\fi

\begin{document}
\includegraphics{image1}
\includegraphics[pdfpng]{image2-converted-to-png-when-mydraft}
\includegraphics{image3}
\end{document}

(\define@key can be used instead of \csname define@key\endcsname, when \makeatletter is active.)