BUG: Clean up imports

skimage/viewer/canvastools/base.py

@@ -1,6 +1,10 @@
 import numpy as np
-import matplotlib as mpl
-from matplotlib import lines
+
+try:
+    import matplotlib as mpl
+    from matplotlib import lines
+except ImportError:
+    print("Could not import matplotlib -- skimage.viewer not available.")
 
 
 __all__ = ['CanvasToolBase', 'ToolHandles']

skimage/viewer/canvastools/line_tool.py

@@ -1,5 +1,9 @@
 import numpy as np
-from matplotlib import lines
+
+try:
+    from matplotlib import lines
+except ImportError:
+    print("Could not import matplotlib -- skimage.viewer not available.")
 
 from base import CanvasToolBase, ToolHandles
 

skimage/viewer/plugins/plotplugin.py

@@ -1,7 +1,14 @@
 import numpy as np
-from PyQt4 import QtGui
 
-import matplotlib.pyplot as plt
+try:
+    from PyQt4 import QtGui
+except ImportError:
+    print("Could not import PyQt4 -- skimage.viewer not available.")
+
+try:
+    import matplotlib.pyplot as plt
+except ImportError:
+    print("Could not import matplotlib -- skimage.viewer not available.")
 
 from ..utils import MatplotlibCanvas
 from .base import Plugin
@@ -18,6 +25,7 @@ class PlotCanvas(MatplotlibCanvas):
         super(PlotCanvas, self).__init__(parent, self.fig, **kwargs)
         self.setMinimumHeight(150)
 
+
 class PlotPlugin(Plugin):
     """Plugin for ImageViewer that contains a plot canvas.
 

viewer_examples/viewers/collection_viewer.py

@@ -18,7 +18,6 @@ home/end keys
     First/last image in collection.
 
 """
-import numpy as np
 from skimage import data
 from skimage.viewer import CollectionViewer
 from skimage.transform import pyramid_gaussian