Today I will explain you how to wrap a C file to call it from python.
I learned it by wrapping the C library from Christophe Geuzaine (http://geuz.org/gl2ps/) which allow you to export an OpenGL scene into a PostScript file (ps, eps, pdf or svg).
First you have to download and install a library called SWIG (http://www.swig.org/), if you are running on Ubuntu this can be easily done by taping the command line :
§ sudo apt-get install swig
Then you have to make a ".i" file to swig, which will be connected to the C header.
Start by opening a text editor and copy this :
%module gl2ps
%{
#include "gl2ps.h"
%}
%typemap(in) FILE* {
$1 = (FILE *) PyFile_AsFile($input);
}
Here we indicate the future name of the module (gl2ps.py) and at which C header it will be linked.
Then you just have to copy all the necessary items from the header, in my case I copied all the lines starting from /* Version number */ , I also removed if defined(_cplusplus) loops, endif /*__GL2PS_H__*/ statement and all the GL2PSDLL_API at the end of the header since I am on Ubuntu and will call this file from python. If you are running on Windows I think that you should past the entire file as it is but I haven't tried to swig on Windows so...
Once it is done just save the text file as gl2ps.i in the same folder than the header and C file. Then just run from the directory where all the files are :
§ swig -python gl2ps.i
This produce two files : gl2ps.py and gl2ps_wrap.c. After that you just have to create a little setup.py which uses distutils to help us compile the wrapped program. This tiny bit of code look like this (Note: to build this requires that OpenGL is currently installed in a common directory) :
from distutils.core import setup, Extension
setup(name="gl2ps",
py_modules=["gl2ps"],
ext_modules=[Extension("_gl2ps",
["gl2ps.c","gl2ps_wrap.c"],
libraries=["GL"])])
That's it ! You just have to run...
§ python setup.py build or § python setup.py build install
...to begin to use your new gl2ps.py module (Note : if you are using it as standalone module in your application the _gl2ps.so file must be in the same folder than the gl2ps.py).
Example of use :
Just as a little key event in the pyglet graphics example.
@window.event
def on_key_press(symbol, modifiers):
if symbol == key.S:
print "let's test it !"
state = GL2PS_OVERFLOW
buffsize = 0
fp = open("torus.eps", "wb")
print "Writing... "
while(state == GL2PS_OVERFLOW):
buffsize += 1024*1024
gl2psBeginPage("test", "gl2psTestSimple", None, GL2PS_EPS, GL2PS_SIMPLE_SORT,
GL2PS_DRAW_BACKGROUND | GL2PS_USE_CURRENT_VIEWPORT,
GL_RGBA, 0, None, 0, 0, 0, buffsize, fp, "torus.eps")
batch.draw()
state = gl2psEndPage()
fp.close()
print "Done!\n"
return pyglet.event.EVENT_HANDLED
