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:
1 2 | skimage/io/_plugins/mpl.pyskimage/io/_plugins/mpl.ini |
The name of the .py and .ini files must correspond. Inside the .ini file, we give the plugin meta-data:
1 2 3 4 | [mpl] <-- name of the plugin, may be anythingdescription = Matplotlib image I/O pluginprovides = 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:
1 2 3 4 5 6 | # This is mpl.pyimport matplotlib.pyplot as pltdef 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:
1 2 | [mpl]provides = imshow, _app_show |
1 2 3 4 5 6 7 8 9 | # This is mpl.pyimport matplotlib.pyplot as pltdef 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:
1 2 3 4 5 6 7 | >>> 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:
1 2 3 | >>> 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:
1 2 | >>> import skimage.io as io>>> io.use_plugin('pil') # Use all capabilities provided by PIL |
or
1 | >>> 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:
1 2 3 4 | >>> io.plugin_info('pil')>>>{'description': 'Image reading via the Python Imaging Library', 'provides': 'imread, imsave'} |
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