matplotlib-users

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

[John H. <jdh...@ac...>]

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

    Kuzminski> I attached a '_gd.dll'.  This is the C python
    Kuzminski> extension that the gd.py module from gdmodule imports.
    Kuzminski> It goes directly in site-packages.  I built it
    Kuzminski> statically linked to zlib, libpng, freetype and the gd
    Kuzminski> lib.  I don't have the time at the moment to fuss with
    Kuzminski> getting it to use the dlls.  ( or to add the jpeg
    Kuzminski> support ) The precompiled windows GD dll in particular
    Kuzminski> seems to not export a few functions that gdmodule
    Kuzminski> wants which is a real pain.

Excellent, the easier the better...


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

Could be that I don't have the text bounding boxes exactly right in
gdmodule.  In axes.py there is a line on or around line 454

if 0:

if you replace that with 

if 1:

the text bounding boxes will be displayed.  If they are not exactly
right, then the text layout will also be off.  I'll take a look when I
get some time, but in the mean time you may want to see for yourself.

Re: gdmodule on windows.  What did you do for fonttools?  Did you also
build this yourself?  If I recall correctly I built it once on windows
without too much difficulty (back when I was trying to get gd working
on windows) but it's been a while and I didn't keep notes.  I didn't
see an installer on the sf site.

JDH


    Kuzminski>         im.writePng( filename )



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

    Kuzminski> thanks, Stefan

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

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

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

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

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

    Kuzminski> Are you using matplotlib + GD for a web app server?

    Kuzminski> John Hunter


 

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

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

The windows GD build is bear.  I had it completely working, then I
upgraded to 0.41 and took a few steps back. =20

First a little background. I'm building a reporting tool for a
commercial analytics platform.  This tool takes an XML specification and
data, and outputs HTML tables and plots.  The larger platform is all
Java, I am providing the reporting as an stand alone ( Python )
executable on Win32, Linux and Solaris.  So my overall requirements are
to create HTML ( and hence .png images ) on all three platforms with a
distribution of a single binary file ( one for each platform ).

Here are some quick notes on what I have had to do, once it is working,
I will provide at least the MSVC makefiles an maybe a binary build, time
permitting. =20

the GD backend has these dependencies..

libpng
zlib
gd
freetype
gdmodule

The 2 main problems I seem to have are that the dll release of GD does
not include a gd.lib. ( MSVC needs a .lib to link with a .dll )  GD does
not seem to come with a windows make file, so I made one. =20

The other problem is that _gdmodule.c needs to have line 1882 changed to
pass a NULL to PYObject_HEAD_INIT=20

...
static PyTypeObject Imagetype =3D {
    PyObject_HEAD_INIT(NULL)
...

I am working on this currently and will post more results as I get them.

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

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

[John H. <jdh...@ac...>]

>>>>> "John" == John Hunter <jdh...@ac...> writes:
    Kuzminski> #2 above is the answer to the problem in my original
    Kuzminski> post. However I have another question.  When I set the
    Kuzminski> ylabel rotation to be horizontal, the beginning of the
    Kuzminski> text is truncated ( the width of the border does not
    Kuzminski> compensate ).  I'm happy to set it wider but am
    Kuzminski> wondering how ( what controls the width of the area
    Kuzminski> where the labels gets written ).  

In this case the placement of the ylabel is determined by the
horizontalalignment and the left side of the y tick labels.  If it is
being truncated, you have a few choices.

  1) Use a different alignment or smaller fontsize for the label

  2) Use a smaller font size for the y tick labels or turn them off
     entirely -- the position of the ylabel will automatically adjust
     based upon the size of the tick labels.

  3) Probably best, make a custom axes where the 'left' parameter is
     larger and the width parameter is smaller.  This will give you
     more room for your ylabel.

    Kuzminski> I also noticed that title of the graph ( with the
    Kuzminski> horizontal alignment set to bottom ) is too close to
    Kuzminski> the top of the graph itself, is there a way to pad
    Kuzminski> that?

When you set the title, do

   t = title('my title')
   t.set_y(1.05)  # relative axes coords

1.0 is the top of the axes, so the larger the number the higher the
title will be.  1.02 is the default.

Hope this helps,
JDH