ENH: Allow Plugin.add_widget to hook into Plugin attributes.

The `ptype` parameter of widget can now be set to 'plugin'. When this is the case, the plugin will set a plugin attribute whenever the widget is updated.

As an example, this commit adds a ComboBox widget which is hooked into the overlay color of the OverlayPlugin.

skimage/viewer/plugins/base.py

@@ -1,7 +1,6 @@
 from PyQt4 import QtGui
 
 import matplotlib as mpl
-from ..widgets import Slider
 
 
 class Plugin(QtGui.QDialog):
@@ -43,6 +42,7 @@ class Plugin(QtGui.QDialog):
         if image_filter is not None:
             self.image_filter = image_filter
 
+        #TODO: Always passing image as first argument may be bad assumption.
         self.arguments = [image_viewer.original_image]
         self.keyword_arguments= {}
 
@@ -86,9 +86,14 @@ class Plugin(QtGui.QDialog):
         elif widget.ptype == 'arg':
             self.arguments.append(widget)
             widget.callback = self.filter_image
+        elif widget.ptype == 'plugin':
+            widget.callback = self.update_plugin
         self.layout.addWidget(widget, self.row, 0)
         self.row += 1
 
+    def update_plugin(self, name, value):
+        setattr(self, name, value)
+
     def closeEvent(self, event):
         """Disconnect all artists and events from ImageViewer.
 

skimage/viewer/plugins/canny.py

@@ -1,7 +1,7 @@
 from skimage.filter import canny
 
 from .overlayplugin import OverlayPlugin
-from ..widgets import Slider
+from ..widgets import Slider, ComboBox
 
 
 class CannyPlugin(OverlayPlugin):
@@ -16,6 +16,7 @@ class CannyPlugin(OverlayPlugin):
         self.add_widget(Slider('sigma', 0, 5, update_on='release'))
         self.add_widget(Slider('low threshold', 0, 255, update_on='release'))
         self.add_widget(Slider('high threshold', 0, 255, update_on='release'))
+        self.add_widget(ComboBox('color', self.color_names, ptype='plugin'))
         # Update image overlay to default slider values.
         self.filter_image()
 

skimage/viewer/plugins/overlayplugin.py

@@ -1,6 +1,5 @@
-from ..utils import clear_red
-
 from .base import Plugin
+from ..utils import ClearColormap
 
 
 class OverlayPlugin(Plugin):
@@ -12,12 +11,19 @@ class OverlayPlugin(Plugin):
         Overlay displayed on top of image. This overlay defaults to a color map
         with alpha values varying linearly from 0 to 1.
     """
+    colors = {'red': (1, 0, 0),
+              'yellow': (1, 1, 0),
+              'green': (0, 1, 0),
+              'cyan': (0, 1, 1)}
 
     def __init__(self, image_viewer, **kwargs):
         Plugin.__init__(self, image_viewer, **kwargs)
-        self.overlay_cmap = clear_red
         self._overlay_plot = None
         self._overlay = None
+        self.cmap = None
+        self.color_names = self.colors.keys()
+        #TODO: `color` doesn't update GUI widget when set manually.
+        self.color = 0
 
     @property
     def overlay(self):
@@ -31,7 +37,7 @@ class OverlayPlugin(Plugin):
             ax.images.remove(self._overlay_plot)
             self._overlay_plot = None
         elif self._overlay_plot is None:
-            self._overlay_plot = ax.imshow(image, cmap=self.overlay_cmap)
+            self._overlay_plot = ax.imshow(image, cmap=self.cmap)
         else:
             self._overlay_plot.set_array(image)
         self.image_viewer.redraw()
@@ -39,3 +45,19 @@ class OverlayPlugin(Plugin):
     def closeEvent(self, event):
         self.overlay = None
         super(OverlayPlugin, self).closeEvent(event)
+
+    @property
+    def color(self):
+        return self._color
+
+    @color.setter
+    def color(self, index):
+        # Update colormap whenever color is changed.
+        name = self.color_names[index]
+        self._color = name
+        rgb = self.colors[name]
+        self.cmap = ClearColormap(rgb)
+
+        if self._overlay_plot is not None:
+            self._overlay_plot.set_cmap(self.cmap)
+        self.image_viewer.redraw()

skimage/viewer/utils/core.py

@@ -3,7 +3,7 @@ import matplotlib.pyplot as plt
 from matplotlib.colors import LinearSegmentedColormap
 
 
-__all__ = ['figimage', 'LinearColormap', 'ClearColormap', 'clear_red']
+__all__ = ['figimage', 'LinearColormap', 'ClearColormap']
 
 
 def figimage(image, scale=1, dpi=None, **kwargs):
@@ -65,13 +65,10 @@ class LinearColormap(LinearSegmentedColormap):
 class ClearColormap(LinearColormap):
     """Color map that varies linearly from alpha = 0 to 1
     """
-    def __init__(self, name, rgb):
+    def __init__(self, rgb, name='clear_color'):
         r, g, b = rgb
         cg_speq = {'blue':  [(0.0, b), (1.0, b)],
                    'green': [(0.0, g), (1.0, g)],
                    'red':   [(0.0, r), (1.0, r)],
                    'alpha': [(0.0, 0.0), (1.0, 1.0)]}
         LinearColormap.__init__(self, name, cg_speq)
-
-clear_red = ClearColormap('clear_red', (0.7, 0, 0))
-

skimage/viewer/widgets/core.py

@@ -1,5 +1,21 @@
+"""
+Widgets for interacting with ImageViewer.
+
+These widgets should be added to a Plugin subclass using its `add_widget`
+method. The Plugin will delegate action based on the widget's parameter type
+specified by its `ptype` attribute, which can be:
+
+    'arg' : positional argument passed to Plugin's `filter_image` method.
+    'kwarg' : keyword argument passed to Plugin's `filter_image` method.
+    'plugin' : attribute of Plugin. You'll probably need to make the attribute
+        a class property that updates the display.
+
+"""
+from PyQt4 import QtGui
+from PyQt4 import QtCore
 from skimage.io._plugins.q_color_mixer import IntelligentSlider
 
+
 class Slider(IntelligentSlider):
     """Slider widget.
 
@@ -12,11 +28,56 @@ class Slider(IntelligentSlider):
         name of the slider.
     low, high : float
         Range of slider values.
-    ptype : {'arg' | 'kwarg' | ...}
-        Parameter
+    ptype : {'arg' | 'kwarg' | 'plugin'}
+        Parameter type.
     """
     def __init__(self, name, low, high, ptype='kwarg', callback=None, **kwargs):
         self.ptype = ptype
         kwargs.setdefault('orientation', 'horizontal')
         scale = (high - low) / 1000.0
         super(Slider, self).__init__(name, scale, low, callback, **kwargs)
+
+
+class ComboBox(QtGui.QWidget):
+    """ComboBox widget for selecting among a list of choices.
+
+    Parameters
+    ----------
+    name : str
+        Name of slider parameter. If this parameter is passed as a keyword
+        argument, it must match the name of that keyword argument (spaces are
+        replaced with underscores). In addition, this name is displayed as the
+        name of the slider.
+    items: list
+        Allowed parameter values.
+    ptype : {'arg' | 'kwarg' | 'plugin'}
+        Parameter type.
+    """
+
+    def __init__(self, name, items, ptype='kwarg', callback=None):
+        super(ComboBox, self).__init__()
+        self.ptype = ptype
+        self.callback = callback
+
+        self.name = name
+        self.name_label = QtGui.QLabel()
+        self.name_label.setText(self.name)
+        self.name_label.setAlignment(QtCore.Qt.AlignLeft)
+
+        self._combo_box = QtGui.QComboBox()
+        self._combo_box.addItems(items)
+
+        self.layout = QtGui.QHBoxLayout(self)
+        self.layout.addWidget(self.name_label)
+        self.layout.addWidget(self._combo_box, alignment=QtCore.Qt.AlignLeft)
+
+        self._combo_box.currentIndexChanged.connect(self._value_changed)
+        # self.connect(self._combo_box,
+                # SIGNAL("currentIndexChanged(int)"), self.updateUi)
+
+    @property
+    def val(self):
+        return self._combo_box.value()
+
+    def _value_changed(self, value):
+        self.callback(self.name, value)