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Re: [Matplotlib-users] Pdf File sizes on newer versions of matplotlib is a lot larger
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From: Michael D. <md...@st...> - 2013-07-31 13:32:04
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On 07/30/2013 04:20 PM, Jeffrey Spencer wrote:
> Michael,
>
> Thanks that is very informative. Answers most of the problems I was
> having and read MEP14 which looks really useful
>
> That being said does the ps backend subset the fonts or use
> collections for drawing (is the collections feature global or just in
> the pdf backend)?
The ps backend has the same behavior as pdf on both counts. TTF fonts
are subsetted, but the fonts that come from TeX come to use as Type1
fonts, which matplotlib currently does not know how to subset. It also
handles collections in the same way (by creating a "stamp" and reusing it).
> I usually use .eps output and convert to pdf using epstopdf unless the
> figure has an alpha channel because always results in a much smaller
> file (60kB roughly for this file or plain figure around 10kB) than
> direct pdf output with the output looking the same. I pretty much
> always have usetex=True so maybe the pdf file is always embedding the
> full fonts.
Yes, when usetex=True, matplotlib does not do any font subsetting (in
any backend). To get around this limitation, one can use the
`pdftocairo` tool (part of poppler utils), to convert from pdf to a pdf
with subsetted fonts. With your example, I was able to get the pdf down
to ~80k. With MEP14, we would basically move such functionality into
matplotlib itself, but that's sort of a long term, semi-back-burner
project so it could be a while.
It's possible that epstopdf is doing some font subsetting of its own.
But as you point out, Postscript (as a specification) doesn't support
alpha, so it's not useful when you need alpha.
>
> Also, does the Cairo backend support usetex=True or subsetting? I know
> I had read it did not support usetex but that was maybe 2 years ago or
> so. The x,y,z axis look correct with cairo but the IPA Fonts don't
> render properly. The legend font says it is size 12 but if you zoom in
> extremely close you can see they are the correct fonts just way to
> small. The file size is around 60kB as well so I am guessing it
> supports subsetting of fonts.
Cairo does support font subsetting, but the matplotlib Cairo backend has
no support for usetex. I'm surprised this worked for you at all. When
I run your example with the Cairo backend, the IPA characters appear as
raw TeX source code, i.e. "\textipa{i}", which is what I would expect
given that the regular font renderer doesn't understand that syntax.
>
> The pgf backend would also subset fonts if output to .pdf I'm assuming
> because that is the default with pdftex? It results in similar size
> files to the .eps output for this file (roughly 60kB also).
Yes.
>
> The IPA font uses the package (\usepackage{tipa}) and therefore that
> is why I think these look differently. That package draws these fonts
> with its' font libraries instead of whatever is selected as the text
> font. Maybe I'm wrong about this but that is my understanding because
> even in normal latex code the fonts look different than the standard text.
That is correct. The default font for usetex=True is Computer Modern,
whereas it is Bitstream Vera Sans in the default font rendering. I was
referring to the difference between 1.2 and 1.4 which was using TeX
fonts in both cases, but due to a bug in 1.3/1.4 was rendering the IPA
in serif when you had requested sans-serif.
Mike
>
> Cheers,
> Jeff
>
>
> On Wed, Jul 31, 2013 at 4:43 AM, Michael Droettboom <md...@st...
> <mailto:md...@st...>> wrote:
>
> There are two different things going on here.
>
> Between 1.2.1 and now, there was a bugfix to the font selection
> routine that inadvertently introduced a bug selecting fonts in the
> usetex backend. You may notice that on master, the IPA font
> selected is different. The file size difference can be attributed
> to the slightly larger font size of the one it selected vs. the
> one it should have. Note that when usetex is True, the fonts are
> not subsetted, so you always get the full font embedded in the
> file (MEP14 work will fix this in the future).
>
> See b5c340 for the bug that introduced the commit, and
> https://github.com/matplotlib/matplotlib/pull/2260 for the fix
> (which should make it into 1.3.0 final).
>
> Between 1.1.1 and 1.2.1 a change was made in how collections are
> handled. Previously, each path was redrawn individually. In 1.2,
> if a path is reused multiple times, a "stamp" is created and then
> it is "used" multiple times. In principle, this generally reduces
> file sizes by a large amount. However, in the case of this figure
> with the 3D spheres, each path is used only once, so rather than
> getting the file size savings of that approach, we only get the
> overhead. The backend could be smarter by not doing this when the
> path is only used a small number of times. Such a fix would be
> welcome, but is probably too large/risky to try to get into the
> current release cycle. It will have to wait for 1.3.1
>
> Cheers,
> Mike
>
>
>
> On 07/30/2013 12:24 PM, Jeffrey Spencer wrote:
>> K, I have just made the script self-contained but it loads
>> external data so I have attached that as well. If you want me to
>> just separate out the plotting commands let me know. I have also
>> attached my matplotlib rc file which is the same on all three
>> systems. All the modifications to the matplotlibrc file are
>> copied to the top and in the first 30 lines or so.
>>
>> Of note, the smallest file sizes for pdf are using the pgf
>> backend around 60kb. Not sure if that helps at all. It is also
>> around the same size if I export to .eps and then convert to pdf.
>> About 60kb. The problem with eps in these 3d figures though is
>> the back wall I think has an alpha channel because just becomes a
>> solid wall in the output. No lines through it like the other two
>> walls.
>>
>>
>> On Tue, Jul 30, 2013 at 11:23 PM, Jouni K. Seppänen <jk...@ik...
>> <mailto:jk...@ik...>> wrote:
>>
>> Jeffrey Spencer <jef...@gm...
>> <mailto:jef...@gm...>> writes:
>>
>> > I have three different versions of matplotlib that all
>> output different
>> > file sizes with matplotlib 1.1.1 providing the smallest.
>> This is for the
>> > same exact script. I can post the script if that helps.
>> >
>> > MPL 1.4.x: 539.32kb, Ubuntu 12.10
>> > MPL 1.1.1: 172.56kb Ubuntu 12.10
>> > MPL 1.2.1: 475.9kb, Ubuntu 13.04
>>
>> Yes, it would be interesting to know what the plotting
>> commands are.
>> Just as a guess, since all the sizes are a few hundred
>> kilobytes, it
>> could be a difference in e.g. font embedding - many TrueType
>> fonts are
>> of comparable size.
>>
>> --
>> Jouni K. Seppänen
>> http://www.iki.fi/jks
>>
>>
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