348 lines
10 KiB
Python
348 lines
10 KiB
Python
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"""Handle image reading, writing and plotting plugins.
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To improve performance, plugins are only loaded as needed. As a result, there
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can be multiple states for a given plugin:
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available: Defined in an *ini file located in `skimage.io._plugins`.
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See also `skimage.io.available_plugins`.
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partial definition: Specified in an *ini file, but not defined in the
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corresponding plugin module. This will raise an error when loaded.
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available but not on this system: Defined in `skimage.io._plugins`, but
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a dependent library (e.g. Qt, PIL) is not available on your system.
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This will raise an error when loaded.
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loaded: The real availability is determined when it's explicitly loaded,
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either because it's one of the default plugins, or because it's
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loaded explicitly by the user.
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"""
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import os.path
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import warnings
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from configparser import ConfigParser
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from glob import glob
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from .collection import imread_collection_wrapper
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__all__ = ['use_plugin', 'call_plugin', 'plugin_info', 'plugin_order',
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'reset_plugins', 'find_available_plugins', 'available_plugins']
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# The plugin store will save a list of *loaded* io functions for each io type
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# (e.g. 'imread', 'imsave', etc.). Plugins are loaded as requested.
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plugin_store = None
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# Dictionary mapping plugin names to a list of functions they provide.
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plugin_provides = {}
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# The module names for the plugins in `skimage.io._plugins`.
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plugin_module_name = {}
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# Meta-data about plugins provided by *.ini files.
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plugin_meta_data = {}
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# For each plugin type, default to the first available plugin as defined by
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# the following preferences.
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preferred_plugins = {
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# Default plugins for all types (overridden by specific types below).
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'all': ['imageio', 'pil', 'matplotlib', 'qt'],
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'imshow': ['matplotlib'],
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'imshow_collection': ['matplotlib']
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}
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def _clear_plugins():
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"""Clear the plugin state to the default, i.e., where no plugins are loaded
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"""
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global plugin_store
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plugin_store = {'imread': [],
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'imsave': [],
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'imshow': [],
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'imread_collection': [],
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'imshow_collection': [],
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'_app_show': []}
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_clear_plugins()
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def _load_preferred_plugins():
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# Load preferred plugin for each io function.
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io_types = ['imsave', 'imshow', 'imread_collection', 'imshow_collection',
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'imread']
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for p_type in io_types:
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_set_plugin(p_type, preferred_plugins['all'])
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plugin_types = (p for p in preferred_plugins.keys() if p != 'all')
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for p_type in plugin_types:
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_set_plugin(p_type, preferred_plugins[p_type])
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def _set_plugin(plugin_type, plugin_list):
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for plugin in plugin_list:
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if plugin not in available_plugins:
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continue
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try:
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use_plugin(plugin, kind=plugin_type)
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break
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except (ImportError, RuntimeError, OSError):
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pass
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def reset_plugins():
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_clear_plugins()
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_load_preferred_plugins()
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def _parse_config_file(filename):
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"""Return plugin name and meta-data dict from plugin config file."""
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parser = ConfigParser()
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parser.read(filename)
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name = parser.sections()[0]
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meta_data = {}
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for opt in parser.options(name):
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meta_data[opt] = parser.get(name, opt)
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return name, meta_data
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def _scan_plugins():
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"""Scan the plugins directory for .ini files and parse them
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to gather plugin meta-data.
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"""
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pd = os.path.dirname(__file__)
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config_files = glob(os.path.join(pd, '_plugins', '*.ini'))
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for filename in config_files:
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name, meta_data = _parse_config_file(filename)
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if 'provides' not in meta_data:
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warnings.warn(f'file {filename} not recognized as a scikit-image io plugin, skipping.')
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continue
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plugin_meta_data[name] = meta_data
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provides = [s.strip() for s in meta_data['provides'].split(',')]
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valid_provides = [p for p in provides if p in plugin_store]
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for p in provides:
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if p not in plugin_store:
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print("Plugin `%s` wants to provide non-existent `%s`."
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" Ignoring." % (name, p))
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# Add plugins that provide 'imread' as provider of 'imread_collection'.
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need_to_add_collection = ('imread_collection' not in valid_provides and
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'imread' in valid_provides)
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if need_to_add_collection:
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valid_provides.append('imread_collection')
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plugin_provides[name] = valid_provides
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plugin_module_name[name] = os.path.basename(filename)[:-4]
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_scan_plugins()
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def find_available_plugins(loaded=False):
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"""List available plugins.
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Parameters
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----------
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loaded : bool
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If True, show only those plugins currently loaded. By default,
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all plugins are shown.
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Returns
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-------
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p : dict
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Dictionary with plugin names as keys and exposed functions as
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values.
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"""
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active_plugins = set()
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for plugin_func in plugin_store.values():
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for plugin, func in plugin_func:
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active_plugins.add(plugin)
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d = {}
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for plugin in plugin_provides:
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if not loaded or plugin in active_plugins:
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d[plugin] = [f for f in plugin_provides[plugin]
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if not f.startswith('_')]
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return d
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available_plugins = find_available_plugins()
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def call_plugin(kind, *args, **kwargs):
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"""Find the appropriate plugin of 'kind' and execute it.
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Parameters
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----------
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kind : {'imshow', 'imsave', 'imread', 'imread_collection'}
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Function to look up.
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plugin : str, optional
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Plugin to load. Defaults to None, in which case the first
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matching plugin is used.
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*args, **kwargs : arguments and keyword arguments
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Passed to the plugin function.
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"""
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if kind not in plugin_store:
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raise ValueError('Invalid function (%s) requested.' % kind)
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plugin_funcs = plugin_store[kind]
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if len(plugin_funcs) == 0:
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msg = ("No suitable plugin registered for %s.\n\n"
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"You may load I/O plugins with the `skimage.io.use_plugin` "
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"command. A list of all available plugins are shown in the "
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"`skimage.io` docstring.")
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raise RuntimeError(msg % kind)
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plugin = kwargs.pop('plugin', None)
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if plugin is None:
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_, func = plugin_funcs[0]
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else:
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_load(plugin)
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try:
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func = [f for (p, f) in plugin_funcs if p == plugin][0]
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except IndexError:
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raise RuntimeError('Could not find the plugin "%s" for %s.' %
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(plugin, kind))
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return func(*args, **kwargs)
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def use_plugin(name, kind=None):
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"""Set the default plugin for a specified operation. The plugin
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will be loaded if it hasn't been already.
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Parameters
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----------
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name : str
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Name of plugin.
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kind : {'imsave', 'imread', 'imshow', 'imread_collection', 'imshow_collection'}, optional
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Set the plugin for this function. By default,
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the plugin is set for all functions.
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See Also
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--------
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available_plugins : List of available plugins
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Examples
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--------
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To use Matplotlib as the default image reader, you would write:
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>>> from skimage import io
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>>> io.use_plugin('matplotlib', 'imread')
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To see a list of available plugins run ``io.available_plugins``. Note that
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this lists plugins that are defined, but the full list may not be usable
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if your system does not have the required libraries installed.
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"""
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if kind is None:
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kind = plugin_store.keys()
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else:
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if kind not in plugin_provides[name]:
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raise RuntimeError("Plugin %s does not support `%s`." %
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(name, kind))
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if kind == 'imshow':
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kind = [kind, '_app_show']
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else:
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kind = [kind]
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_load(name)
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for k in kind:
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if k not in plugin_store:
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raise RuntimeError("'%s' is not a known plugin function." % k)
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funcs = plugin_store[k]
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# Shuffle the plugins so that the requested plugin stands first
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# in line
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funcs = [(n, f) for (n, f) in funcs if n == name] + \
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[(n, f) for (n, f) in funcs if n != name]
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plugin_store[k] = funcs
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def _inject_imread_collection_if_needed(module):
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"""Add `imread_collection` to module if not already present."""
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if not hasattr(module, 'imread_collection') and hasattr(module, 'imread'):
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imread = getattr(module, 'imread')
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func = imread_collection_wrapper(imread)
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setattr(module, 'imread_collection', func)
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def _load(plugin):
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"""Load the given plugin.
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Parameters
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----------
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plugin : str
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Name of plugin to load.
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See Also
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--------
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plugins : List of available plugins
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"""
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if plugin in find_available_plugins(loaded=True):
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return
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if plugin not in plugin_module_name:
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raise ValueError("Plugin %s not found." % plugin)
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else:
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modname = plugin_module_name[plugin]
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plugin_module = __import__('skimage.io._plugins.' + modname,
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fromlist=[modname])
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provides = plugin_provides[plugin]
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for p in provides:
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if p == 'imread_collection':
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_inject_imread_collection_if_needed(plugin_module)
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elif not hasattr(plugin_module, p):
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print("Plugin %s does not provide %s as advertised. Ignoring." %
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(plugin, p))
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continue
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store = plugin_store[p]
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func = getattr(plugin_module, p)
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if not (plugin, func) in store:
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store.append((plugin, func))
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def plugin_info(plugin):
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"""Return plugin meta-data.
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Parameters
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----------
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plugin : str
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Name of plugin.
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Returns
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-------
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m : dict
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Meta data as specified in plugin ``.ini``.
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"""
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try:
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return plugin_meta_data[plugin]
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except KeyError:
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raise ValueError('No information on plugin "%s"' % plugin)
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def plugin_order():
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"""Return the currently preferred plugin order.
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Returns
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-------
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p : dict
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Dictionary of preferred plugin order, with function name as key and
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plugins (in order of preference) as value.
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"""
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p = {}
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for func in plugin_store:
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p[func] = [plugin_name for (plugin_name, f) in plugin_store[func]]
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return p
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