Problem with a very heavy EPS image - scatter plot too heavy as EPS

Question

Using Stata, I produced a scatter plot of some variables. I saved the image as an EPS file. There are around a 1000 dots in the scatter plot - and this makes the EPS file to be 26MB. I need to use this image in my LaTeX file (I use TeXnicCenter and compile as LaTeX => PS => PDF). The problem is that it produces a PDF file that takes a long time to load the page displaying the image. I don't need this image to be super sharp - there is no real point in zooming it in too much. Furthermore, the PDF I get is quite heavy for a 16 pages document. Is there anything I could do to improve the loading time of the page with the drawing, and decreasing the size of the PDF file? For example,

1. Would it be an improvement if I convert the image to JPEG, PNG, or BMP? Would it decrease the image size?

2. Is there a way to tell LaTeX to keep using the EPS image, but decrease the quality of the image?

Answer 1

As noted in the comments on the question, EPS is not an ideal way to store the plot. For scatter plots with many points and also for pseudo colour plots, it's a better idea to store the plot itself (without axes and annotations) as a raster graphic such as a PNG. In the case of a pseudo colour plot, this is actually minimal and no information is lost. See this answer for an example I did of one.

As a sample, I plotted random points in octave and then turned off the axes. After saving as a PNG file, I used imagemagick to trim the margins from the plot to produce scatter.png:

Using pgfplots I wrapped this PNG in axes, thus minimising the the space and processing required by the points in the plot. This requires the use of pdflatex rather than latex with a PNG file.

\documentclass[10pt]{article}
\usepackage{pgfplots}
\pgfplotsset{width=6cm,compat=newest}

\begin{document}

\begin{figure}[ht]
\centering
\begin{tikzpicture}
    \begin{axis} [
        scale only axis,        % Plot size does not include axes.
        enlargelimits=false,    % Shrink wrap the PNG.
        axis on top,            % Axes placed over PNG to avoid obscuring the lines.
        xlabel=$x$,
        ylabel=$y$,
    ]
        \addplot graphics [
            xmin=0,
            xmax=1,
            ymin=0,
            ymax=1,
        ] {scatter.png};
    \end{axis}
\end{tikzpicture}
\caption{A simple example.}
\end{figure}

\end{document}

Answer 2

You could load the epstopdf package or the epspdfconversion package to convert the .eps file to a .pdf file "on the fly". The first time you compile your LaTeX program (going directly from .tex to .pdf, without the "detour" via .ps), a format conversion from .eps to .pdf will be performed on the graphics file. Thereafter, LaTeX will know to load the (much smaller) PDF-formatted graphics file directly, saving much compilation time; the size of the output pdf file may shrink as well, but that depends importantly on the nature of the contents of the eps file that's being converted to pdf.

Here's an interesting excerpt from the user guide of the epspdfconversion package:

I [the package's author] am using this package for the inclusion of EPS-figures (or .pdf or .ps) that are produced en-masse by a software packages like Stata... The package makes sure that I can include the EPS-figures easily and the updating of the corresponding PDF's is done "on-the-fly".

For more information on embedding various graphics files using pdf(la)tex, I recommend you go to Imported graphics in PDFLaTeX from the TeX FAQ document.

Answer 3

I already saw comments where you got a recommendation to use ImageMagick to convert your EPS file to PNG image file format. Based on my own experience I would suggest that you use GraphicsMagick (ImageMagick's cousin) to convert your image in one of lossy compression image file formats like JPEG for example before converting it back to EPS format. Then compare the size of your original EPS file and new EPS file. For anybody who would like to start ImageMagick vs GraphicsMagick flame war I have one comment. Please, use both tools on the same image or even on the large collection of images and then compare the size of resulting image files, quality of images and if you have little time on your hands do the speed test. Then make your pick.