[vtkusers] Make part of an Image transparent-HELP PLEASE

[Janny Dong]

Hello all,

I'd like to overlay a RGB image (a geographic map) on top of my rendering
scene in VTK. The map should mask out the ocean part, so the rendering scene
only display within land part. How can I make part of the map transparent?
So far the image I have displays the land part in white. How can I make the
white color transparent, while the blue (ocean part) totally opaque? I know
in photoshop I can make one color transparent. But when I load the image to
VTK, the image lost the transparency. The image reader in VTK only read in
RGB channels?

If I can use vtkImageThreshold, what parameter should I apply threshold to?
I am not sure how I can add an alpha mask to my image, and/or combine the
image and the scene to one image. Could anyone shed some light on this?

Thanks!
Janny
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