Re: [Matplotlib-users] how to reduce the file size of plots generated with matplotlib

[Andrea G. <and...@gm...>]

On 22 March 2014 20:23, Christopher Kuhlman wrote:

> Hello:
>
> I use matplotlib to generate x-y data plots; i.e., 2-D plots.  The problem
> is that the output files (the PDF files containing plots that are generated
> with matplotlib) are huge.  I can generate files that are 100's of KB or
> even MBs.  This seems absurd to me.  These file sizes cause programs that
> use them to come to a grinding halt.  My goal is to reduce the plot files
> that I produce with matplotlib.  Details follow.
>
>
> ----------
>
> I use matplotlib from EPD.
> Enthought Canopy Python 2.7.3 | 64-bit | (default, Aug  8 2013, 05:37:06)
>
> Matplotlib version:
> >>> print matplotlib.__version__
> 1.3.0
>
> OS:
> I'm using Mac OS X Version 10.8.4.
>
> ----------
>
> I use a home-grown code whose starting point was an example code on
> matplotlib website.
>
> My relevant imports are:
>
> import numpy
> import scipy
> import pylab
> import matplotlib.pyplot as plt
> import matplotlib
>
> My plotting code lines are:
>
>
>         ## PDF.
>         outfile = "basefile" + ".pdf"
>         ## pylab.savefig(outfile, bbox_inches=0)
>         pylab.savefig(outfile,bbox_inches='tight')
>
>
> ----------
>
> My PDF files contain simple plots which consist of (a) data points only,
> (b) lines between data points (data points not plotted), or (c) both data
> points and lines.
>
> I have a consistent problem in that the files produced have sizes that
> seem way too big.
> For example, most recently, I am plotting 3 data sets; each data set has
> about 90,000 points.  If I plot all three sets in one PDF figure, the file
> size is over 2MB.
>


There is no way ever that a human eye (or the computer screen) is going to
distinguish or even see 90,000 points on a standard line-plot. Especially
if you reduce it to a 3 inch by 3 inch graph. You may want to
downscale/interpolate your data to a more manageable set of points and try
again. I'm no expert of the PDF side of things, but I agree with Goyo that
raster files may give you smaller file sizes.




> This seems absurd to me.  I used R plotting for many years (again, my own
> homegrown code, for 6 years) and never had this issue, and I was making
> these kinds of plots/figures.
>
> I thought it may be a vector/raster issue, but the following web page says
> that PDF are generated as vector image, which, to my understanding (which
> could be wrong), is the more compact format.
> http://matplotlib.org/faq/usage_faq.html
>
> Is there a command I can use to reduce the file size?  Since I am using
> these in reports and publications, the figures are almost always less than
> 3 inches by 3 inches in size; i.e., I do not have issues about taking a
> raster figure and trying to blow it up.  So I am not concerned about
> pixelation problems that occur when an image is increased in size.
>
> Thank you very much.
>
> c
>
>
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-- 
Andrea.

"Imagination Is The Only Weapon In The War Against Reality."
http://www.infinity77.net

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