[vtk-developers] Simple, efficent greyscale conversion

[David Gobbi]

Hi Everyone,

A couple days ago I staged a patch for vtkScalarsToColors that makes
it into a concrete class that does a simple rescaling of the input scalars
rather than doing a color mapping.  I haven't merged it yet, because I
thought I should ask the other developers first.

Rationale:

1) I hate always having to write out the several lines of code that
are needed to create a greyscale LookupTable.  With this change
I can just do vtkScalarsToColors::New() and, voila, I have a
greyscale scalars-to-colors mapper.

2) By calling SetVectorModeToRGBColors(), which I added recently,
I can also have it convert RGB colors of any datatype to unsigned
char colors.  Very useful when data uses floats for colors, or if I have
unsigned char colors that I want to window/level.

3) This avoids the NAN check and other expensive bits of the
code in vtkLookupTable, so it provides a more efficent way of
displaying greyscale images than vtkLookupTable.  Though I
suspect the difference is slight.

Any thoughts?

 - David