vtkMapper::InterpolateScalarsBeforeMapping and off-screen rendering
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
Off-screen rendering using scalar interpolation before mapping uses more colors than requested by vtkLookupTable::SetNumberOfTableValues.
I installed VTK6.3.0 using the standalone installer. The included script will produce an on-screen image that has the expected number of colors, and a png file that has more colors. The number of extra colors depends on the number of table values specified. Switching off InterpolateScalarsBeforeMapping will give the proper number of colors in the png file.