[vtk-developers] New vector modes for vtkScalarsToColors

Nicolas Rannou Nicolas_Rannou at hms.harvard.edu
Thu Apr 28 13:12:05 EDT 2011

Thanks for the quick answer David,

On Apr 28, 2011, at 12:16 PM, David Gobbi wrote:

> On Thu, Apr 28, 2011 at 9:36 AM, Nicolas Rannou
> <Nicolas_Rannou at hms.harvard.edu> wrote:
>> Hi David,
>> Sorry for the late reply... We are now ready to step into this problem.
>> We have N images corresponding to N channels.
> I thought you had one image with N channels (i.e. one N-component
> image), that is the only situation where my proposal is useful.  For N
> images each with its own channel, you should do something entirely
> different:
> image_1 -> vtkImageMapToColors (with LUT #1) -> vtkImageWeightedSum -> display
> image_2 -> vtkImageMapToColors (with LUT #2) ---/^

We will go to this solution.

>> Is it what you suggested or did I misunderstand you?
> I proposed that vtkScalarsToColors could simultaneously apply
> different tables to different channels _in a single image_ , and then
> combine the results (e.g. by summing the colors resulting from each
> channel and clamping to a max value of 255).  So a pipeline using this
> proposed capability would include only vtkScalarsToColors and
> vtkImageMapToColors.  No other classes would be needed.  (But note
> that this doesn't fit your situation, since you have N images, rather
> than one image with N channels).
> The reasons for adding this ability to vtkScalarsToColors rather than
> making a new lookup-table class are (1) adding it to
> vtkScalarsToColors would allow this multi-capability to be used with
> both lookup tables and with color-transfer functions and (2)
> vtkLookupTable does not subclass as well as you might think, because
> of the way it is implemented its subclasses can only change its
> behavior in trivial ways.
> - David



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