matplotlib-users Mailing List for matplotlib

matplotlib is great, particularly the image quality. I'm using 
matplotlib to generate images in a webapp and have run into a problem. 
How do I get it to give me the rendered image bytes in a string rather 
than writing the image to a file?
The docs for FigureCanvasAgg.print_figure() says that if the filename is 
actually a file object then it will write the bytes to that file object. 
This works great if I pass in sys.stdout, but as soon as I try to use a 
StringIO() instance to capture the bytes in Python I get an error:
 File 
"/usr/lib/python2.3/site-packages/matplotlib/backends/backend_agg.py", 
line 453, in print_figure
 self.renderer._renderer.write_png(filename)
TypeError: Could not convert object to file pointer
The same use of StringIO does work with GD; is this a bug in the Agg 
backend? Please see attached test code.
BTW, while I'm here, I noticed a discusison on matplotlib-devel about 
how to specify the image format when rendering it to the backend:
 
http://www.mail-archive.com/mat...@li.../msg00150.html
I'm in favour of an explicit format argument as well, for exactly the 
webapp use case. I'd like to easily be able to get the bytes for either 
the PNG or SVG of an image.

On Tuesday 15 August 2006 16:05, sg...@ol... wrote:
> Thank you very much.
>
> What I would like is example for embedding_in_qt.py but whith qt4
>
> when I tried :
>
> import PyQt4
> from PyQt4.QtCore import *
> from PyQt4.QtGui import *
>
> from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as
> FigureCanvas
> from matplotlib.figure import Figure
>
> but I have :
>
> Traceback (most recent call last):
You should be doing this instead:
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
Darren

Thank you very much.
What I would like is example for embedding_in_qt.py but whith qt4
when I tried :
import PyQt4
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as
FigureCanvas
from matplotlib.figure import Figure
but I have :
Traceback (most recent call last):
 File "embedding_in_qt.py", line 26, in ?
 from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as
FigureCanvas
 File
"/usr/lib/python2.4/site-packages/matplotlib/backends/backend_qtagg.py",
line 12, in ?
 from backend_qt import qt, FigureManagerQT, FigureCanvasQT,\
 File
"/usr/lib/python2.4/site-packages/matplotlib/backends/backend_qt.py",
line 18, in ?
 import qt
RuntimeError: the qt and PyQt4.QtCore modules both wrap the QObject class
I have a debian sid machine and the package python-matplotlib depends on
python-qt3. But the package python-qt4 exists.
Any ideas what to do ?
Samuel

Daniel Kornhauser wrote:
> I looked at the other wx examples, and even if they are great examples 
> (And I would like to thank a lot the original author Jeremy O'Donoghue 
> ;-) ), they could afford some cleaning up to conform to the wx style guide:
> http://wiki.wxpython.org/index.cgi/wxPython_Style_Guide
> 
> Do you think such a clean up, would be welcomed ?
I think it's a great idea -- but then, I'm the primary author of that 
style guide ;-)
-Chris
-- 
Christopher Barker, Ph.D.
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Chr...@no...

Yes. Trying running a script like so:
python examples/simple_plot-py -dQt4Agg
On 8/15/06, sg...@ol... <sg...@ol...> wrote:
> Is matplotlib compatible whith PyQt4 ?
>
> Thank you
>
> samuel
>
>
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Is matplotlib compatible whith PyQt4 ?
Thank you
samuel

Hi Guys:
> John> many wx users have contributed new/better/more/different wx
> John> examples (embedding_in_wx[1-4].py) to atone for the original
> 
Another suggestion that I would like to make is to change the name of 
the examples. I think all the examples that have to do with a particular 
backed should be prefixed with the name of the toolkit. I think this is 
important since the new users can see at a glance all the examples that 
are related to wx.
Thus I think the name or the rewritten wxcursor_demo.py should be 
changed to embedding_in_wx_cursor.py, sounds awful, but it's 
understandable and more practical.
Another option is to put it next to the cursor example and rename it 
from wxcursor_demo.py to cursor_demo_wx.py
I looked at the other wx examples, and even if they are great examples 
(And I would like to thank a lot the original author Jeremy O'Donoghue 
;-) ), they could afford some cleaning up to conform to the wx style guide:
 http://wiki.wxpython.org/index.cgi/wxPython_Style_Guide
Do you think such a clean up, would be welcomed ?
> BTW, have you seen the matplotlib native cursoring, which uses
> matplotlib or drawing rather than native wx.
>
> examples/widgets/cursor.py
> 
Thanks for the tip John, but I found it too slow for my application (I 
change a spectrogram in another figure in function of the pixel where 
cursor is located).
Furthermore native cursoring does not support several cursor pointer 
shapes does it ?
It only supports the cross doesn't it ?
 
 Daniel

>>>>> "John" == John Hunter <jdh...@ac...> writes:
 John> But the example was written a long time ago and since then
 John> many wx users have contributed new/better/more/different wx
 John> examples (embedding_in_wx[1-4].py) to atone for the original
Please forgive everything I wrote as the rantings of a deranged
lunatic. I now see you were talking about the *cursor* demo, not the
*embedding* demo.....
BTW, have you seen the matplotlib native cursoring, which uses
matplotlib or drawing rather than native wx.
 examples/widgets/cursor.py
JDH

>>>>> "Daniel" == Daniel Kornhauser <kor...@re...> writes:
 Daniel> This said, I thank a lot the person who started the
 Daniel> example since I used it as a starting point.
You should also thank that person because he (Jeremy O'Donoghue)
wrote the wx backend <wink>. 
But the example was written a long time ago and since then many wx
users have contributed new/better/more/different wx examples
(embedding_in_wx[1-4].py) to atone for the original sins. I'm happy
to use your new/more/better/different example, but I'll first defer to
the wisdom of the resident wxperts, who may have some comments.
JDH

I am making a new wxcursor_demo.py example I attach it to this mail.
If anybody can help me iron those wrinkles I think we can make a great 
wxcursor_demo example.
I am not proud of invoking the SetCursor method on the wx.EVT_PAINT 
event but it works ...
The present wxcursor_demo example is broken because:
 - Does not follow wx coding standards, not pythonic at all.
 - Very complicated example to follow and long.
 - Some nonsensical code such as the Time and Price part.
 - The wx "hand draw", crosshair has lots of disadvantages (you get 
the mouse pointer right next to it so it's useless for picking pixels in 
images.)
 - The users should have access to wx.StockCursor, with the current 
example every cursor has to be " hand drawn"
 This said, I thank a lot the person who started the example 
since I used it as a starting point.
 Any feedback would be appreciated.
 
 
 Daniel.