[Insight-developers] FW: [Insight-users] GradientImageFilter vs GradientRecursiveGauss ianImageFilter

[Miller, James V (Research)]

Josh,

The GradientImageFilter uses the DerivativeOperator.  Is this filter using the
DerivativeOperator incorrectly? Or are the coefficient signs flipped?

Jim

-----Original Message-----
From: Pieter Vos [mailto:pieterv@nat-239.azn.nl]
Sent: Thursday, April 25, 2002 5:55 AM
To: insight-users@public.kitware.com
Subject: [Insight-users] GradientImageFilter vs
GradientRecursiveGaussianImageFilter


Hello,

I compaired the outputs of the filter GradientImageFilter and the
GradientRecursiveGaussianImageFilter.
Both filters had the same 3D image: a black image with a white spot in the
middle. The vectoroutputs however, where not the same:

The vectors of the GradientImageFilter where pointing away form the spot.

------------------
|
|	^
|	|
|    <-   ->
|    <-   ->
|       |
|	
|
------------------

And the vectors of the GradientRecursiveGaussian where pointing to the
white spot:

------------------
|
|
|        |
|    ->     <-
|    ->     <-
|        ^
|        |
|
------------------

The second picture is as how it should be. 

So, am I forgetting some basic theory (and should I study again)
or should the outcome of the GradientImageFilter not be the opposite?

Please help.

Greetings,

-- 
Pieter Vos
UMC Radboud Nijmegen
The Netherlands
mailto:pieterv@radiology.azn.nl

_______________________________________________
Insight-users mailing list
Insight-users@public.kitware.com
http://public.kitware.com/mailman/listinfo/insight-users