Ignore blanked cells in vtkCellDataToPointData.

Change-Id: Id3ed7c5f65cc6eadae32db36e41dff1a786c527b
6657: Add out-of-range colors to color maps

This change adds special colors to color maps that can optionally be
used for scalar values outside the range of the color map. It touches
a number of classes in VTK.

vtkLookupTable

- Added AboveRangeColor for values above the lookup table range.

- Added UseAboveRangeColor option to control whether the
  AboveRangeColor or the color that maps to the highest value is used
  for values above the range.

- Added BelowRangeColor for values below the lookup table range.

- Added UseBelowRangeColor option to control whether the
  BelowRangeColor or the color that maps to the lowest value is used
  for values below the range.

- Made GetColorAsUnsignedChars() a static member so that other classes
  can use it.

TestLookupTable

- Modified test to include testing of {Above|Below}RangeColors
  functionality.

TestOutOfRangeColorTransferFunction.py

- Test of out-of-range color functionality in
  vtkColorTransferFunction.

TestOutOfRangeDiscretizableColorTransferFunction.py

- Test of out-of-range color functionality in
  vtkDiscretizableColorTransferFunction.

vtkScalarsToColors

- Made RGBABytes member protected so subclasses can use it.

vtkColorTransferFunction

- Added {Above|Below}RangeColor and Use{Above|Below}RangeColor member
  variables that function the same as the members with the same name
  in vtkLookupTable. These colors are specified as RGB colors instead
  of RGBA colors, as they are in vtkLookupTable. For better or worse,
  this is for consistency with how NanColor is specified in each of
  these classes.

- Above and BelowRangeColor are used only if the Clamping option is
  enabled.

vtkDiscretizableColorTransferFunction

- Forwards {Above|Below}RangeColor and Use{Above|Below}RangeColor to
  the internal vtkLookupTable in the Build() method.

- Fixed a bug that caused the internal vtkLookupTable to allocate
  3 times the amount of colors needed to hold the table.

vtkScalarsToColorsPainter

- Added two colors for {Above|Below}RangeColors in the lookup table
  texture map. The color map class fills in these colors appropriately
  based on the {Above|Below}RangeColors settings.

- Fixed the texture coordinate calculation to accommodate out-of-range
  colors.

Performance-wise, this change increases the time to map an array with
10 million scalars to colors by 5.5% using
vtkLookupTable::MapScalarsThroughTable2().

Change-Id: Ia3535fae175e991c0d1a4cf70752845193b4166d
Add render mode in which values are drawn as recoverable 24bit colors.

With this you can pick an array component and draw that directly
on the screen. Afterward, if you know the min and max, you read pixel
values back and get a hold of the value at each pixel.

TODO:
* Lots of type conversion here, and in the end only using 24 bits
of resolution. When and if we need more accuracy, flesh out
the extensible conversion operator part.
* Surface selection is based on the same concept (ident buffer)
but that was written before VTK has extensible rendering (painters
and passes). Eventually selection should be reimplemented to use
this.
* Would be great to demonstrate render into background followed by
mouse overs.

Change-Id: I44608759278c37c8250f957d596f3f4149382bbb
Merge topic 'blanked-cell-data' into master

7bb258f1 Ignore blanked cells in vtkCellDataToPointData.
Merge topic 'value-rendering' into master

f8c5c678 Add render mode in which values are drawn as recoverable 24bit colors.
Merge topic '6657_add_out_of_range_colors' into master

238163f9 6657: Add out-of-range colors to color maps
COMP: Include "vtk_glew.h" instead of "GL/glew.h"

The former properly selects between the VTK-provided and system glew
header.

Change-Id: If39ed4762ce2c4d0ba80248083e8a8e8371fd5c4
Merge topic 'opengl2-include-vtk_glew' into master

c2db066e COMP: Include "vtk_glew.h" instead of "GL/glew.h"
fix a compilation warning

Change-Id: I472c993f7d14c756815110ae9bdc34a0b61d6890
Merge topic 'value-rendering' into master

c46f50c5 fix a compilation warning
Fix test failure

Change-Id: I8d28302ef33df637892619cdca8e4949f8d8b804
Merge topic 'value-rendering' into master

9446581e Fix test failure