matplotlib-users

[Matplotlib-users] font rendering quality

[Ernest A. <ead...@gm...>]

Hi,
I notice a big difference in quality between the text rendered
by matplotlib and that rendered by the rest of applications.
As an example, see the image attached showing the same font as
shown by firefox and matplotlib respectively.
Is there any config setting I can change to improve the font
rendering or anything?

Cheers.

Re: [Matplotlib-users] font rendering quality

[John H. <jd...@gm...>]

On Mon, Nov 30, 2009 at 6:38 PM, Ernest Adrogué <ead...@gm...> wrote:
> Hi,
> I notice a big difference in quality between the text rendered
> by matplotlib and that rendered by the rest of applications.
> As an example, see the image attached showing the same font as
> shown by firefox and matplotlib respectively.
> Is there any config setting I can change to improve the font
> rendering or anything?


The two examples in the page you link to have different font sizes and
possibly different font weights, which makes it difficult to do
side-by-side comparisons.  Could you post an example with
similar/identical settings?

JDH

Re: [Matplotlib-users] font rendering quality

[Ernest A. <ead...@gm...>]

30/11/09 @ 22:28 (-0600), thus spake John Hunter:
> The two examples in the page you link to have different font sizes and
> possibly different font weights, which makes it difficult to do
> side-by-side comparisons.  Could you post an example with
> similar/identical settings?

Yes, I have attached another example with different font sizes
(8,9,10). The exact weight is impossible to replicate, I tried with
"light" and "normal".

I think that the problem might be the lack of hinting. In my
fonts.conf file I have both "hinting" and "autohinting" enabled. if
I disable these options then the fonts in other applications resemble
a lot the ones I am getting now with mpl.

Bye.

Re: [Matplotlib-users] font rendering quality

[Darren D. <dsd...@gm...>]

On Tue, Dec 1, 2009 at 6:37 AM, Ernest Adrogué <ead...@gm...> wrote:
> 30/11/09 @ 22:28 (-0600), thus spake John Hunter:
>> The two examples in the page you link to have different font sizes and
>> possibly different font weights, which makes it difficult to do
>> side-by-side comparisons.  Could you post an example with
>> similar/identical settings?
>
> Yes, I have attached another example with different font sizes
> (8,9,10). The exact weight is impossible to replicate, I tried with
> "light" and "normal".
>
> I think that the problem might be the lack of hinting. In my
> fonts.conf file I have both "hinting" and "autohinting" enabled. if
> I disable these options then the fonts in other applications resemble
> a lot the ones I am getting now with mpl.

I am pretty sure the issue here is subpixel rendering. Try comparing
the output of the gtkagg backend, which does not do subpixel
rendering, with that of gtkcairo, which does.

Darren

Re: [Matplotlib-users] font rendering quality

[Michael D. <md...@st...>]

Subpixel rendering is almost never what you want when producing a PNG 
file, since it is likely to be shared on a different machine requiring 
different subpixel settings.  But it looks like your mozilla example is 
not using subpixel rendering either, though it appears to have very 
strong hinting.

matplotlib's Agg backends borrows a technique used by Adobe Acrobat 
which is to use strong hinting in the vertical direction, but more 
subtle hinting in the horizontal.  When we did a comprehensive 
comparison of various hinting options about two years ago it was the 
strong winner.  See this:

   
http://www.mail-archive.com/mat...@li.../msg01480.html

(Unfortunately, the linked images are no longer available).

If these settings are not to your liking, I would recommend the Cairo 
backend (which should pull in the same settings as the rest of your 
Gnome desktop, I believe), or one of the vector backends and then 
tweaking the rendering.

Alternatively, we could provide this "stretched hinting" as a 
configuration option.  If you think that's superior to these other 
options, please file a feature request so it doesn't get lost (and it 
should be a fairly straightforward patch for someone new to the code base.)

Mike

Darren Dale wrote:
> On Tue, Dec 1, 2009 at 6:37 AM, Ernest Adrogué <ead...@gm...> wrote:
>   
>> 30/11/09 @ 22:28 (-0600), thus spake John Hunter:
>>     
>>> The two examples in the page you link to have different font sizes and
>>> possibly different font weights, which makes it difficult to do
>>> side-by-side comparisons.  Could you post an example with
>>> similar/identical settings?
>>>       
>> Yes, I have attached another example with different font sizes
>> (8,9,10). The exact weight is impossible to replicate, I tried with
>> "light" and "normal".
>>
>> I think that the problem might be the lack of hinting. In my
>> fonts.conf file I have both "hinting" and "autohinting" enabled. if
>> I disable these options then the fonts in other applications resemble
>> a lot the ones I am getting now with mpl.
>>     
>
> I am pretty sure the issue here is subpixel rendering. Try comparing
> the output of the gtkagg backend, which does not do subpixel
> rendering, with that of gtkcairo, which does.
>
> Darren
>
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-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Re: [Matplotlib-users] font rendering quality

[Ernest A. <ead...@gm...>]

 1/12/09 @ 09:16 (-0500), thus spake Michael Droettboom:
> Subpixel rendering is almost never what you want when producing a
> PNG file, since it is likely to be shared on a different machine
> requiring different subpixel settings.  But it looks like your
> mozilla example is not using subpixel rendering either, though it
> appears to have very strong hinting.

Yes, it's not a subpixel rendering problem. I can tell that
subpixel rendering is not enabled because I'm not seeing "rainbows",
which I always see when it's enabled. It's definitely a hinting issue.

> matplotlib's Agg backends borrows a technique used by Adobe Acrobat
> which is to use strong hinting in the vertical direction, but more
> subtle hinting in the horizontal.  When we did a comprehensive
> comparison of various hinting options about two years ago it was the
> strong winner.  See this:
> 
> http://www.mail-archive.com/mat...@li.../msg01480.html
> 
> (Unfortunately, the linked images are no longer available).
> 
> If these settings are not to your liking, I would recommend the
> Cairo backend (which should pull in the same settings as the rest of
> your Gnome desktop, I believe), or one of the vector backends and
> then tweaking the rendering.

Confirmed. The GTK backend -haven't tried Cairo yet- honours the
system settings for font rendering. It looks much better now, in my
opinion.

> Alternatively, we could provide this "stretched hinting" as a
> configuration option.  If you think that's superior to these other
> options, please file a feature request so it doesn't get lost (and
> it should be a fairly straightforward patch for someone new to the
> code base.)

Ok. I will open a feature request, if you think it's okay.
I think I'll be sticking with the GTK backend for now, anyway.

Thanks.
Ernest