[vtkusers] question abotu output spacing for the reslicer

[David Gobbi]

Hi Luca,

You are correct about the interpolation part, but the spacing works 
opposite to the way you guessed.

If you want to zoom the image by a factor of 2.0, you should set the 
OutputSpacing to half of the original image spacing.

A good way to explain it is like this.  The OutputSpacing is the size of 
the output pixels.  So, if you have an MRI image that covers a square 
area of 256mm by 256mm, if the OutputSpacing is 1mm then the number of 
pixels in the output image will be 256x256.  If the OutputSpacing is 
0.5mm, the number of pixels will be 512x512.

 - David



Luca Pamparana wrote:
> Hi everyone,
>
> I was wondering what exactly the OutputSpacing parameters are doing to 
> the input image.
>
> So, if I double the OutputSpacing in the x and y direction, I can 
> achieve a zoom of factor 2.0.
>
> However, what does it mean for the pixels in the output image? So, one 
> data pixel now takes 2 pixels in the x and y directions. How is the 
> data for these pixels calculated? Does the slicer take the adjacent 
> pixel and interpolates based on the interpolation scheme selected?
>
> I know this is a very basic question but I will be grateful if someone 
> can answer this.
>
> Thanks,
>
> Luc
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