[vtk-developers] Extracting component while loading PNG files

[Pierre Barbier de Reuille]

Hello,

As of now, when you load a (set of) PNG image(s), if the PNG was saved
as palette, it will be loaded as RGB(A). The problem is, most PNG
converted I know will always create palette-PNGs, event if the image is
gray-scaled. That means, you end up using 3 times the memory really
needed to load the image. Moreover, you need to add a
vtkExtractComponent object, which add another copy of the data. In my
case, I have 512x512x512 volumetric data, and this copy of the data is
just too much.

So I modified vtkPNGReader to allow the user to specify if he wants to
extract one of the components while loading. I attach the patch to this
mail.

I think it might be good to add that directly to vtkImageReader2.
However, I am unsure of the correct way to do this (ie. did I propose a
correct interface or not), and also about the fact that you might want
this kind of functionality in the image readers.

Thank you,

Pierre
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