[Insight-users] How to cast from RGB to short?

[Gaëtan Lehmann]

Le 31 août 09 à 15:33, Michael Xanadu a écrit :

> Hi,
>
> I've got a watershed filtered image processed by a colormapper. So  
> it's an image of type:
>
>     typedef itk::RGBPixel<short>   RGBPixelType;
>     typedef itk::Image<RGBPixelType, 2>    RGBImageType;
>
> Now I want to filter that image with a connected threshold filter,  
> because I need it this way.
> But ConnectedThresholdImageFilter can't process such RGB images.
> I tryed to convert the image into a short type by using  
> CastImageFilter, too.
> But I always get:
>
>     error C2440: 'static_cast' : cannot convert from  
> 'itk::RGBPixel<TComponent>' to 'short'
>
> So how can I cast from RGB to short? Or how to filter a RGB image  
> with a connected threshold filter?
>

You can extract one of the channels with  
VectorIndexSelectionCastImageFilter or go to an intensity image with  
RGBToLuminanceImageFilter, but I doubt that's what you want. The color  
image is only a representation of the watershed output easier to read  
for humans, but not for computer. If you want to work on the output of  
the watershed, it's better to not use a color mapper, but directly on  
the output image of the watershed - the image should be of type  
itk::Image< unsigned long, 2 >.

And even if you don't use a color mapper, it may not be a good idea to  
process the output of the watershed filter (a labeled image) with a  
filter (ConnectedThresholdImageFilter) made to work on a grayscale  
images.

Can you explain what you want to achieve?

Regards,

Gaëtan

-- 
Gaëtan Lehmann
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
http://voxel.jouy.inra.fr  http://www.itk.org
http://www.mandriva.org  http://www.bepo.fr

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