On Thu, May 31, 2012 at 4:08 PM, David Doria <daviddo...@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
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