Second part of I/O infrastructure reorganisation.

scikits/image/io/__init__.py

@@ -1,10 +1,11 @@
 """Utilities to read and write images in various formats."""
 
-import pil_plugin
-import matplotlib_plugin
-import qt_plugin
+from _plugins import load as load_plugin
+from _plugins import use as use_plugin
+from _plugins import available as plugins
 
-from plugin import register as register_plugin
+# Add this plugin so that we can read images by default
+import _plugins.pil_plugin as _pil_plugin
 
 from sift import *
 from collection import *

scikits/image/io/_plugins/matplotlib_plugin.py

@@ -2,7 +2,7 @@ import plugin
 
 try:
     import matplotlib.pyplot as plt
-except ImportError:
-    pass
+except ImportError, e:
+    print e
 else:
     plugin.register('matplotlib', show=plt.imshow, save=plt.imsave)

scikits/image/io/_plugins/pil_plugin.py

@@ -1,7 +1,7 @@
 __all__ = ['imread']
 
-import numpy as np
 import plugin
+import numpy as np
 
 try:
     from PIL import Image
@@ -51,4 +51,4 @@ def palette_is_grayscale(pil_image):
 
 
 if has_pil:
-    plugin.register('PIL', read=imread)
+    plugin.register('pil', read=imread)

scikits/image/io/_plugins/plugin.py

@@ -2,7 +2,7 @@
 
 """
 
-__all__ = ['register', 'use']
+__all__ = ['register', 'use', 'load', 'available', 'call']
 
 import warnings
 
@@ -38,7 +38,7 @@ def register(name, **kwds):
         if not callable(func):
             raise ValueError('Can only register functions as plugins.')
 
-        plugin_store[kind].append((name, func))
+        plugin_store[kind].insert(0, (name, func))
 
 
 def call(kind, *args, **kwargs):
@@ -60,7 +60,11 @@ def call(kind, *args, **kwargs):
 
     plugin_funcs = plugin_store[kind]
     if len(plugin_funcs) == 0:
-        raise RuntimeError('No suitable plugin registered for %s' % kind)
+        raise RuntimeError('''No suitable plugin registered for %s.
+
+You may load I/O plugins with the `scikits.image.io.load_plugin`
+command.  A list of all available plugins can be found using
+`scikits.image.io.plugins()`.''' % kind)
 
     plugin = kwargs.pop('plugin', None)
     if plugin is None:
@@ -123,8 +127,9 @@ def available(kind=None):
     Parameters
     ----------
     kind : {'show', 'save', 'read'}, optional
-        Display the plugin list for the given function type.  If not specified,
-        return a dictionary with the plugins for all functions.
+        Display the plugin list for the given function type.  If not
+        specified, return a dictionary with the plugins for all
+        functions.
 
     """
     if kind is None:
@@ -141,3 +146,21 @@ def available(kind=None):
         d[k] = [name for (name, func) in plugin_store[k]]
 
     return d
+
+def load(plugin):
+    """Load the given plugin.
+
+    Parameters
+    ----------
+    plugin : str
+        Name of plugin to load.
+
+    See Also
+    --------
+    plugins : List of available plugins
+
+    """
+    try:
+        __import__('scikits.image.io._plugins.' + plugin + "_plugin")
+    except ImportError:
+        raise ValueError('Plugin %s not found.' % plugin)

scikits/image/io/_plugins/qt_plugin.py

@@ -1,5 +1,5 @@
 import plugin
-from _plugin_util import prepare_for_display
+from util import prepare_for_display
 
 import numpy as np
 import sys
@@ -37,7 +37,7 @@ else:
     def show(arr, block=True):
         global app
 
-        if not '-q4thread' in sys.argv and app is None:
+        if not '-qt4thread' in sys.argv and app is None:
             app = QApplication([])
 
         arr = prepare_for_display(arr)

scikits/image/io/_plugins/wx_plugin.py

@@ -1,6 +1,6 @@
 import numpy as np
 import plugin
-from _plugin_util import prepare_for_display
+from util import prepare_for_display
 
 try:
     import wx

scikits/image/io/io.py

@@ -1,6 +1,6 @@
 __all__ = ['imread', 'imsave', 'imshow']
 
-from scikits.image.io import plugin as _plugin
+from scikits.image.io._plugins import call as call_plugin
 
 def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
            **plugin_args):
@@ -44,8 +44,8 @@ def imread(fname, as_grey=False, dtype=None, plugin=None, flatten=None,
     if flatten is not None:
         as_grey = flatten
 
-    return _plugin.call('read', fname, as_grey=as_grey, dtype=dtype,
-                        plugin=plugin, **plugin_args)
+    return call_plugin('read', fname, as_grey=as_grey, dtype=dtype,
+                       plugin=plugin, **plugin_args)
 
 def imsave(fname, arr, plugin=None, **plugin_args):
     """Save an image to file.
@@ -67,7 +67,7 @@ def imsave(fname, arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    return _plugin.call('save', fname, arr, plugin=plugin, **plugin_args)
+    return call_plugin('save', fname, arr, plugin=plugin, **plugin_args)
 
 def imshow(arr, plugin=None, **plugin_args):
     """Display an image.
@@ -87,4 +87,4 @@ def imshow(arr, plugin=None, **plugin_args):
         Passed to the given plugin.
 
     """
-    return _plugin.call('show', arr, plugin=plugin, **plugin_args)
+    return call_plugin('show', arr, plugin=plugin, **plugin_args)

scikits/image/io/tests/test_imread.py

@@ -3,7 +3,7 @@ import numpy as np
 
 from scikits.image import data_dir
 from scikits.image.io import imread
-from scikits.image.io.pil_plugin import palette_is_grayscale
+from scikits.image.io._plugins.pil_plugin import palette_is_grayscale
 
 def test_imread_flatten():
     # a color image is flattened and returned as float32

scikits/image/io/tests/test_plugin.py

@@ -1,7 +1,7 @@
 from numpy.testing import *
 
 from scikits.image import io
-from scikits.image.io import plugin
+from scikits.image.io._plugins import plugin
 
 from copy import deepcopy
 
@@ -23,7 +23,7 @@ def show_other(arr):
 
 def setup_module(self):
     self.backup_plugin_store = deepcopy(plugin.plugin_store)
-    plugin.register('test', read=read, save=save, show=show)
+    plugin.register('testcase', read=read, save=save, show=show)
     plugin.register('other', show=show_other)
 
 def teardown_module(self):
@@ -31,13 +31,13 @@ def teardown_module(self):
 
 class TestPlugin:
     def test_read(self):
-        io.imread('test.png', as_grey=True, dtype='i4', plugin='test')
+        io.imread('test.png', as_grey=True, dtype='i4', plugin='testcase')
 
     def test_save(self):
-        io.imsave('test.png', [1, 2, 3], plugin='test')
+        io.imsave('test.png', [1, 2, 3], plugin='testcase')
 
     def test_show(self):
-        io.imshow([1, 2, 3], plugin_arg=(1, 2), plugin='test')
+        io.imshow([1, 2, 3], plugin_arg=(1, 2), plugin='testcase')
 
     def test_use(self):
         plugin.use('other', 'show')
@@ -48,5 +48,12 @@ class TestPlugin:
         d = plugin.available('show')
         assert d['show'][0] == 'other'
 
+    def test_load(self):
+        plugin.load('test')
+        fname, arr = io.imsave('outfile', [1, 2, 3])
+        assert_equal(fname, 'outfile')
+        assert_equal(arr, [1, 2, 3])
+        assert_equal(plugin.available('save')['save'][0], 'test')
+
 if __name__ == "__main__":
     run_module_suite()