FW: [Matplotlib-users] broken PNG files with GD backend

[Kuzminski, S. R <SKu...@fa...>]

Some notes on compiling GD backend for windows.

1) _gdmodule.c needs to be modified in 2 places to compile on windows=20

	a) line 1888 PyObject_HEAD_INIT() needs to passed a NULL.  This
is in the Python docs.
=09
....
	static PyTypeObject Imagetype =3D {
    		PyObject_HEAD_INIT(NULL)
    		0,                                  /*ob_size*/
....

	b) the init_gd function ( line 1957 ) needs to have
'_declspec(dllexport)' added to the declaration.=20

.....
/* Initialization function for the module (*must* be called init_gd) */
void _declspec(dllexport) init_gd(void)
{=20
....

2) This one took me a long time to figure out.  For some reason opening
a windows file in Python with 'wb' permission will cause the png files
to be corrupted above a certain image size.  If you pass the filename to
gdmodule, then the gdmodule opens the file and it works.  I imagine that
the python call "open( 'filename', 'wb' )" just calls fopen, furthermore
I thought that binary mode only applied to reading files.  At any rate,
I have no idea why this doesn't work in this case but it doesn't.  To
get it to work, I had to change line 261 in backends_gd.py to pass the
filename rather than a file object, this is the only modification to
Matplotlib I had to make.

        im.writePng( filename )



#2 above is the answer to the problem in my original post. However I
have another question.  When I set the ylabel rotation to be horizontal,
the beginning of the text is truncated ( the width of the border does
not compensate ).  I'm happy to set it wider but am wondering how ( what
controls the width of the area where the labels gets written ).  I also
noticed that title of the graph ( with the horizontal alignment set to
bottom ) is too close to the top of the graph itself, is there a way to
pad that?

thanks,
Stefan

-----Original Message-----
From: John Hunter [mailto:jdh...@ni...]=20
Sent: Friday, January 23, 2004 6:58 AM
To: Kuzminski, Stefan R
Cc: mat...@li...
Subject: Re: [Matplotlib-users] broken PNG files with GD backend

>>>>> "Kuzminski," =3D=3D Kuzminski, Stefan R <SKu...@fa...>
writes:

    Kuzminski> Now on to my specific problem.  I'm using the GD
    Kuzminski> backend on Windows with Matplotlib 0.41. =20

First things first -- I haven't succeeded in getting the gd backend
compiled on windows.  If you have some expertise here and are willing
to share, or better yet build a gdmodule and gd installer that I can
put on the website, I would be very much obliged!  I contacted the
gdmodule maintainer some time ago over this issue and he had never
built it on windows either.  In my googling, I discovered the perl gd
module for windows and following their lead, succeeded in building gd
lib, but ran into some troubles (can't remember what) building
gdmodule.

    Kuzminski> If I set the dpi to over 60 the png file that gets
    Kuzminski> generated is 'empty', it's only 17 bytes long.  As soon
    Kuzminski> as I drop he DPI to below 65 or so, I get the image
    Kuzminski> file correctly.  This is with the simple_plot.py
    Kuzminski> example.

Now on to your problem. Is there a typo here?  You say over 60 is
empty and under 65 is ok ??  Can you send me a script which replicates
the problem, with the two calls to savefig, one which has the problem
and which does not.  Then I can begin to diagnose the problem; see if
it occurs under linux, see if it's a gd problem, see if it's a problem
on my end, etc....

Are you using matplotlib + GD for a web app server? =20

John Hunter=20


=20