[Insight-users] convert to gray scale image

[Luis Ibanez]

Hi Beck,

Here are some options:

A) Use ImageAdaptors. You decide how to convert color to
   grayscale and encode such conversion in the PixelAccessor.
   Please read the SoftwareGuide for details.
   http://www.itk.org/ItkSoftwareGuide.pdf
   Chapter 12, pdf-page 521.

B) Use the UnaryFunctor filter. This is very similar to
   Adaptors. In this case you simply encode the color to
   grayscale conversion into a Functor. Then instantiate
   the UnaryFunctorFilter using your Functor.
   You can look at filters like the AsinImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1AsinImageFilter.html
   in order to get an idea on how to do this.


C) If your image is coming straight from a file, you could
   simply instantiate the input image as being of a single
   scalar type.  The ImageIO classes convert color to grayscale
   when needed.  The drawback here is that you don't have any
   control on the conversion process.



---

A Bonus: note that there are region growing methods that will
operate directly on RGB images. For example:

http://www.itk.org/Insight/Doxygen/html/classitk_1_1VectorConfidenceConnectedImageFilter.html


There is also a LevelSet filter (similar to thresholding +
region growing + regularization) that accepts vector images
(therefore RGB images).
http://www.itk.org/Insight/Doxygen/html/classitk_1_1VectorThresholdSegmentationLevelSetImageFilter.html



   Regards,


      Luis



--------------
Beck wrote:

> Dear All:
> I want to use NeighborhoodConnectedImageFilter and my images are full 
> color images.
> So I want to convert color images to gray scale images as input for 
> NeighborhoodConnectedImageFilter.
> How can I convert color images to gray scale images?
> Hope anyone can help.
>  
> Thanks
>  
> Beck