I/O Plugin Infrastructure
A plugin consists of two files, the source and the descriptor .ini
. Let’s say we’d like to provide a plugin for imshow
using matplotlib
. We’ll call our plugin mpl
:
skimage/io/_plugins/mpl.py skimage/io/_plugins/mpl.ini
The name of the .py
and .ini
files must correspond. Inside the .ini
file, we give the plugin meta-data:
[mpl] <-- name of the plugin, may be anything description = Matplotlib image I/O plugin provides = imshow <-- a comma-separated list, one or more of imshow, imsave, imread, _app_show
The “provides”-line lists all the functions provided by the plugin. Since our plugin provides imshow
, we have to define it inside mpl.py
:
# This is mpl.py import matplotlib.pyplot as plt def imshow(img): plt.imshow(img)
Note that, by default, imshow
is non-blocking, so a special function _app_show
must be provided to block the GUI. We can modify our plugin to provide it as follows:
[mpl] provides = imshow, _app_show
# This is mpl.py import matplotlib.pyplot as plt def imshow(img): plt.imshow(img) def _app_show(): plt.show()
Any plugin in the _plugins
directory is automatically examined by skimage.io
upon import. You may list all the plugins on your system:
>>> import skimage.io as io >>> io.find_available_plugins() {'gtk': ['imshow'], 'matplotlib': ['imshow', 'imread', 'imread_collection'], 'pil': ['imread', 'imsave', 'imread_collection'], 'qt': ['imshow', 'imsave', 'imread', 'imread_collection'], 'test': ['imsave', 'imshow', 'imread', 'imread_collection'],}
or only those already loaded:
>>> io.find_available_plugins(loaded=True) {'matplotlib': ['imshow', 'imread', 'imread_collection'], 'pil': ['imread', 'imsave', 'imread_collection']}
A plugin is loaded using the use_plugin
command:
>>> import skimage.io as io >>> io.use_plugin('pil') # Use all capabilities provided by PIL
or
>>> io.use_plugin('pil', 'imread') # Use only the imread capability of PIL
Note that, if more than one plugin provides certain functionality, the last plugin loaded is used.
To query a plugin’s capabilities, use plugin_info
:
>>> io.plugin_info('pil') >>> {'description': 'Image reading via the Python Imaging Library', 'provides': 'imread, imsave'}
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