[Paraview] Thresholding an image

[David Doria]

On Thu, May 31, 2012 at 4:08 PM, David Doria <daviddoria at gmail.com> wrote:

> I am trying to look for the pixels in an image whose magnitude are
> above a certain value. I loaded the image, then tried to use the
> Threshold filter. The tooltip says "Requires an attribute array with 1
> component."
>
> Question 1) Would it make sense to allow this filter to operate on one
> of the channels of the image instead of having to extract it manually?
>
> To generate this attribute array, I used the Calculator filter to make
> an array called AbsX with abs(MetaImage_X). Then I applied a Threshold
> filter to this new array. The values in this array are in [0 512].
> When I leave the Lower Threshold all the way down and the Upper
> Threshold all the way up, I can view the image just fine. In the
> Display tab, the Color By is set to AbsX, like I want. However, as
> soon as I move the Lower Threshold slider, the image disappears. When
> I look in the Display tab, the only option for Color By is now Solid
> Color.
>
> Question 2) Why would the Color By options change based on the
> threshold that is set? (I'd also ask why the image is disappearing,
> but I think it might have to do with the coloring).
>
> If I then try to glyph the output of the threshold filter (to draw
> spheres or something at the location of the pixels that remain), the
> Scalars option of the glyphs shows my AbsX array, but it is not
> enabled. The only choice is under Vectors, and it is my MetaImage
> array.
>
> Question 3) Why can I not glyph the AbsX array?
>
> Sorry for the long winded question, but hopefully someone can shed
> some light on these issues!
>
> Thanks,
>
> David
>

Any thoughts on this? Is it just impossible, or am I missing something?

David
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.paraview.org/pipermail/paraview/attachments/20120604/94dd1a17/attachment.htm>