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.. _faq:
==========================
Frequently Asked Questions
==========================
Installation
============
.. _faq-linker-cant-find-libufo:
Why can't the linker find libufo.so?
----------------------------------------
In the rare circumstances that you installed UFO from source for the first time
by calling ``make install``, the dynamic linker does not know that the library
exists. If this is the case issue ::
$ sudo ldconfig
on Debian systems or ::
$ su
$ ldconfig
on openSUSE systems.
If this is not working, the library is neither installed into ``/usr/lib`` nor
``/usr/local/lib`` on 32-bit systems or ``/usr/lib64`` and ``/usr/local/lib64``
on 64-bit systems.
Usage
=====
.. _faq-filter-not-found:
Why do I get a "libfilter<foo>.so not found" message?
-------------------------------------------------------
Because the UFO core system is unable to locate the filters. By default it looks
into ``${LIBDIR}/ufo``. If you don't want to install the filters system-wide,
you can tell the system to try other paths as well by appending paths to the
``UFO_PLUGIN_PATH`` :ref:`environment variable <using-env>`.
Can I split a linear data stream?
---------------------------------
The output data stream of a node can be split by setting the
``UFO_SEND_SEQUENTIAL`` mode and adjusting the number of expecting data items on
each connected node::
from gi.repository import Ufo
out_node.set_send_pattern(Ufo.SendPattern.SEQUENTIAL)
in1_node.set_num_expected(0, 5) # expect five items on the first input
in2_node.set_num_expected(0, -1) # expect all items
g = Ufo.TaskGraph()
g.connect_nodes(out_node, in1_node)
g.connect_nodes(out_node, in2_node)
The connection order matters here! If it would be reversed, ``in2_node`` would
receive all items whereas ``in1_node`` wouldn't receive anything.
How can I control the debug output from libufo?
-----------------------------------------------
Generally, UFO emits debug messages under the log domain ``Ufo``. If you use a
UFO-based tool and cannot see debug messages, you might have to enable them by
setting the ``G_MESSAGES_DEBUG`` environment variable, i.e.::
export G_MESSAGES_DEBUG=Ufo
To handle these messages from within a script or program, you must set a log
handler_ that decides what to do with the messages. To ignore all messages in
Python, you would have to write something like this::
from gi.repository import Ufo, GLib
def ignore_message(domain, level, message, user):
pass
if __name__ == '__main__':
GLib.log_set_handler("Ufo", GLib.LogLevelFlags.LEVEL_MASK,
ignore_message, None)
.. _handler: http://developer.gnome.org/glib/unstable/glib-Message-Logging.html#g-log-set-handler
.. _faq-numpy-output:
How can I use Numpy output?
---------------------------
Install the ``ufo-python-tools``. You can then use the BufferInput filter to
process Numpy arrays data::
from gi.repository import Ufo
import ufo.numpy
import numpy as np
arrays = [ i*np.eye(100, dtype=np.float32) for i in range(1, 10) ]
buffers = [ ufo.numpy.fromarray(a) for a in arrays ]
pm = Ufo.PluginManager()
numpy_input = pm.get_task('bufferinput')
numpy_input.set_properties(buffers=buffers)
.. _faq-synchronize-properties:
How can I synchronize two properties?
-------------------------------------
Although this is a general GObject question, synchronizing two properties is
particularly important if the receiving filter depends on a changed property.
For example, the back-projection should start only if a center-of-rotation is
known. In Python you can use the ``bind_property`` function from the
``ufotools`` module like this::
from gi.repository import Ufo
import ufotools.bind_property
pm = Ufo.PluginManager()
cor = g.get_task('centerofrotation')
bp = g.get_task('backproject')
# Now connect the properties
ufotools.bind_property(cor, 'center', bp, 'axis-pos')
In C, the similar ``g_object_bind_property`` function is provided out-of-the-box.
|
