matplotlib-users Mailing List for matplotlib (Page 12)

Vedpathak, Rameshwari IN BLR SISL wrote:
> Hello,
> 
> As mentioned in the
> site(http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig)
> dpi is the resolution in dots per inch.
> When we change dpi the size of the figure gets changed. But we want the
> resolution to be changed and not the figure size.
> 
> Can anyone give more information on 'dpi' parameter.
READ THIS MAILING LIST! AND THE WIKI!
There was just a discussion about this on this list last week, which 
resulted in this post to the Wiki:
http://www.scipy.org/wikis/topical_software/AdjustingImageSize
Please feel free to improve that Wiki page, or if something is unclear, 
or doesn't work, post a question here about it.
-Chris
-- 
Christopher Barker, Ph.D.
Oceanographer
 		
NOAA/OR&R/HAZMAT (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chr...@no...

Chris Fonnesbeck wrote:
>I think there is more to it than that. There are all sorts of
>dependencies on either Numeric or numarray that need to be addressed.
>Try installing matplotlib without either Numeric or numarray -- I dont
>think you will get very far.
> 
>
Ah, good point. It would be good to begin work on this, but IMHO the 
new scipy_core has a bit to go before it is ready for prime time. 
Someone just pointed out on the numpy list, for example, that it 
presently does not include masked arrays, a capability I use often and 
support for which was painstakingly added to Matplotlib over the last 
year or so.

Rameshwari,
I think everyone else has given you enough pointers on increasing the 
resolution of your plots, I just thought I'd chime in w/ more info on JPEG.
JPEG is lossy compression format - it throws away information. PNG is a 
loss-less compression format - it does not throw away information. Since 
both formats start from the same raster image, you cannot increase your 
picture quality by changing formats, only by changing the original 
raster. In particular, JPEG is a terrible format for plots. It was 
designed to compress pictures and it cannot deal well with rapid changes in 
color in a image (like a black line on a white background).
Most JPEG compressed plots will show artifacts around all of the lines so 
instead of seeing the pixels (for a black line on a white background) like 
this:
 white, white, white, black, white, white, white
In a JPEG image, you would see:
 white, grey, grey, black, grey, grey, white
As others have already indicates, you can increase your DPI through various 
means or switch to PS (which uses vector based drawing commands instead of 
a set of pixels).
Ted
At 05:38 AM 10/3/2005, Vedpathak, Rameshwari IN BLR SISL wrote:
>Hello,
>
>We are using matplotlib version 0.8 (matplotlib-0.80.win32-py2.2.exe).
>
>The plots are saved as .png, but we feel the quality of this picture is 
>not so good. (not good resolution supported).
>Is there anyway by which we can improve the picture quality? Say like by 
>using .jpeg.
>
>We tried to save the plot as .jpeg as mentioned on the site 
>(<http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig>http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig) 
>, but we get error "IOError: Do not know know to handle extension *.jpeg...."
>Does it mean that matplotlib 0.8 does not support jpeg format?
>
>If anyone has an idea about this then please do let us know.
>
>Thanks in advance
>
>Best Regards,
>Rameshwari
Ted Drain Jet Propulsion Laboratory ted...@jp... 

Hi there,
I have some data whose x values supposed to be centered around 0. So I'd like 
to position the y-axis at x=0, but centered in the plot (e.g. -1<=x<=1).
I'm a matplotlib newbie (from what I've seen so far it rocks btw), but as it 
stands it seems impossible to do this with the axes() command. On the goals 
page I came across "Detachable axis from main axes box and customizable 
tickline locations" which seems to aim for functionality which could do this.
So, my question is: Can I center my y-axis in current versions of matplotlib 
(am currently using 0.80-r1 on gentoo) and if so, how? If not, what's the 
implementation status of this new feature?
Thanks.
-- 
Kilian Hagemann
Climate Systems Analysis Group
University of Cape Town
Republic of South Africa
Tel(w): ++27 21 650 2748

Hi there,
I have some data whose x values supposed to be centered around 0. So I'd like 
to position the y-axis at x=0, but centered in the plot (e.g. -1<=x<=1).
I'm a matplotlib newbie (from what I've seen so far it rocks btw), but as it 
stands it seems impossible to do this with the axes() command. On the goals 
page I came across "Detachable axis from main axes box and customizable 
tickline locations" which seems to aim for functionality which could do this.
So, my question is: Can I center my y-axis in current versions of matplotlib 
(am currently using 0.80-r1 on gentoo) and if so, how? If not, what's the 
implementation status of this new feature?
Thanks.
-- 
Kilian Hagemann
5 Myburgh Close
Ruyteplaats Estate
7806 Hout Bay
Tel(w): (021) 650 2748
Tel(m): 082 768 9830
Tel(h): (021) 685 7206

Try changing the resolution to a value of 300 or 600 dpi. This should =
give you very high quality figures when using the Agg backend. The =
standard is 80 which is ok for screen display but for printing purposes =
you should use a higher value. See =
http://matplotlib.sourceforge.net/matplotlib.pylab.html#-figure (dpi =
keyword argument).
 ----- Original Message -----=20
 From: Vedpathak, Rameshwari IN BLR SISL=20
 To: mat...@li...=20
 Sent: Monday, October 03, 2005 2:38 PM
 Subject: [Matplotlib-users] picture quality of the figures
 Hello,
 We are using matplotlib version 0.8 (matplotlib-0.80.win32-py2.2.exe).
 The plots are saved as .png, but we feel the quality of this picture =
is not so good. (not good resolution supported).
 Is there anyway by which we can improve the picture quality? Say like =
by using .jpeg.=20
 We tried to save the plot as .jpeg as mentioned on the site =
(http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig) , =
but we get error "IOError: Do not know know to handle extension =
*.jpeg...."
 Does it mean that matplotlib 0.8 does not support jpeg format?
 If anyone has an idea about this then please do let us know.
 Thanks in advance
 Best Regards,
 Rameshwari

>>>>> "Vedpathak," == Vedpathak, Rameshwari IN BLR SISL <Ram...@si...> writes:
 Vedpathak> Hello, As mentioned in the
 Vedpathak> site(http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig)
 Vedpathak> dpi is the resolution in dots per inch. When we
 Vedpathak> change dpi the size of the figure gets changed. But we
 Vedpathak> want the resolution to be changed and not the figure
 Vedpathak> size.
 
 Vedpathak> Can anyone give more information on 'dpi' parameter.
 
The figure size in pixels is width*dpi by height*dpi. png is a raster
format which means it stores the information in a pixel buffer. You
cannot get higher resolution without changing the figure size in
pixels. If you want a higher resolution picture, set the dpi to a
higher number.
Alternatively, as others have suggested, use a vector output like PS
or SVG.
JPEG will not give you a better picture quality -- usually it will be
worse for lines and such.
JDH
 

> We are using matplotlib version 0.8 (matplotlib-0.80.win32-py2.2.exe).
>
> The plots are saved as .png, but we feel the quality of this picture is
> not so good. (not good resolution supported).
> Is there anyway by which we can improve the picture quality? Say like by
> using .jpeg.
 Jpeg is will not be better- it is also a compressed format.
 A better quality can be obtained with postscript (*.ps) or encapsulated=20
postscript (*.eps)
> We tried to save the plot as .jpeg as mentioned on the site
> (http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig) ,
> but we get error "IOError: Do not know know to handle extension
> *.jpeg...."
> Does it mean that matplotlib 0.8 does not support jpeg format?
 Try with .jpg, not .jpeg
	Vincent
=2D-=20
Vincent Favre-Nicolin
Universit=E9 Joseph Fourier
http://v.favrenicolin.free.fr
ObjCryst & Fox : http://objcryst.sourceforge.net

Hello,
=20
As mentioned in the
site(http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig)
dpi is the resolution in dots per inch.
When we change dpi the size of the figure gets changed. But we want the
resolution to be changed and not the figure size.
=20
Can anyone give more information on 'dpi' parameter.
=20
Thanks in advance
=20
Best Regards,
Rameshwari
=20
=20

Hello,
=20
We are using matplotlib version 0.8 (matplotlib-0.80.win32-py2.2.exe).
=20
The plots are saved as .png, but we feel the quality of this picture is
not so good. (not good resolution supported).
Is there anyway by which we can improve the picture quality? Say like by
using .jpeg.=20
=20
We tried to save the plot as .jpeg as mentioned on the site
(http://matplotlib.sourceforge.net/matplotlib.pylab.html#-savefig) ,
but we get error "IOError: Do not know know to handle extension
*.jpeg...."
Does it mean that matplotlib 0.8 does not support jpeg format?
=20
If anyone has an idea about this then please do let us know.
=20
Thanks in advance
=20
Best Regards,
Rameshwari

> Date: 2005年10月01日 18:11:00 -0700
> From: Stephen Walton <ste...@cs...>
> CC: mat...@li...
> Subject: Re: [Matplotlib-users] matplotlib and scipy_core
>
> Chris Fonnesbeck wrote:
>
> >Any idea how easy it will be to use matplotlib with scipy_core?
> >
> At the moment it looks trivial. I have matplotlib 0.84 and "new scipy"
> installed and did:
>
> ipython -pylab
> import scipy as S
> x=3DS.arange(10)
> plot(x,x**2)
>
> and got a plot.
>
I think there is more to it than that. There are all sorts of
dependencies on either Numeric or numarray that need to be addressed.
Try installing matplotlib without either Numeric or numarray -- I dont
think you will get very far.
C.

FYI: Here's a sample script for the bug report (if I understand what you're 
trying to do).
Add the following line to the polar_demo.py right before show:
ax.set_rmax( .8 )
And then you get the attached picture. It looks like the polar axis 
doesn't respond to changes in the maximum radial value to display (even 
though the axis implements the set_rmax method just for that).
Ted
At 12:38 PM 9/30/2005, Stephen Boulet wrote:
>
>
>Thanks for the response.
>
>I have a plot that has a maximum magnitude of about 0.2. I'd like to set the
>radius of the plot circle to 1.
>
>Stephen
>
>
>-------------------------------------------------------
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Chris Fonnesbeck wrote:
>Any idea how easy it will be to use matplotlib with scipy_core?
>
At the moment it looks trivial. I have matplotlib 0.84 and "new scipy" 
installed and did:
ipython -pylab
import scipy as S
x=S.arange(10)
plot(x,x**2)
and got a plot.

One more thought:
John Hunter wrote:
> However, AFAIK, MPL does not have a way to set
> Chris> the pixel size directly.
> 
> It does now. In 0.84 I added a canvas.resize(w,h) in pixels. So far
> this has only been implemented in GTK*.
What about with savefig()? As long as we can set ppi there, it would be 
nice to set a pixel size of the Figure as well.
-Chris
-- 
Christopher Barker, Ph.D.
Oceanographer
 		
NOAA/OR&R/HAZMAT (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chr...@no...

 
 > >>>>> "Stephen" == Stephen Boulet <stephen@th...> writes:
 > 
 > Stephen> Is there a way to set the size of a polar plot (similar
 > Stephen> to the axis argument to the plot command for a
 > Stephen> rectangular plot)? Thanks.
 > 
 > Hmmm. I do not believe the plot command takes an axis argument.
 > 
 > Do you mean the "axes" and "subplot" commands which are used to set
 > the size of the Axes that contains the plot? If so, just pass 
 > polar=True to them, as in
 > 
 > subplot(111, polar=True)
 > axes([0.2, 0.2, 0.7, 0.7], polar=True)
 > 
 > I am updating the axes doc string.
 > 
 > API users, note that the same applies to fig.add_axes and
 > fig.add_subplot.
 > 
 > JDH
Thanks for the response.
I have a plot that has a maximum magnitude of about 0.2. I'd like to set the
radius of the plot circle to 1. 
Stephen

Chris Barker wrote:
> I think I'll update my demo and maybe post it to the Wiki.
Done.
http://www.scipy.org/wikis/topical_software/AdjustingImageSize
-Chris
-- 
Christopher Barker, Ph.D.
Oceanographer
 		
NOAA/OR&R/HAZMAT (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chr...@no...

Hello, I am having trouble because the transparency doesn't work when
you specify a marker color and type:
This transparency works:
Plot([1,2,3,4], alpha=0.1)
This transparency doesn't work:
Plot([1,2,3,4], 'ro', alpha=0.1)
I know this bug has already been posted. I was wondering if there is a
way to get around it? ... or was wondering when it might be fixed? 
Thanks again for the help!
Jeff