*****************
Volume editor
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The central high-level component of Volumina is the volume
editor. It comprises most of the Volumina features and can be
easily incorporated in other (Qt-based) applications. The following figure shows the Qt volume editor widget:

.. _fig-volumina-ortho-views:
.. figure:: img/volumina-ortho-views.jpg
   :width: 640px

   Volume editor widget. The widget shows three slicings trough the
   spatial axes of a three dimensional dataset with two channels
   rendered as a red-green composite image at time slice 0 of 4.

Other widgets are also included like a viewer for 2d images and a
layer widget that allows to control the order and appearance of
different layers in the slice views. Furthermore, a standalone viewer
application is part of Volumina, too. The viewer can be used
in a Python command prompt to inspect multidimensional datasets and
is launched with a simple ``view(dataset)`` call.

Code example
------------
The following code example illustrates the central steps to display
multidimensional data in several layers with Volumina::

  # construct some data sources from raw data
  source = ArraySource(npy_array)
  rgb    = ArraySource(npy_rgbarray)

  # define layers and store them in a layerstack
  layerstack = LayerStackModel()

  layer1 = GrayscaleLayer( source )
  layer1.name = "Raw Data"
  layerstack.append(layer1)    

  layer2 = RGBALayer(red=rgb[..., 0],
		     green=rgb[..., 1],
		     alpha=rgb[..., 2])
  layer2.name = "RGB Layer"
  layer2.opacity = 0.5
  layerstack.append(layer1)

  # instantiate a volume editor and display the layers
  editor = VolumeEditor(shape, layerstack)
  widget = VolumeEditorWidget( editor )
  widget.show()