[Insight-developers] Center computations wrong?

[Dieter Hahn]

Hi,
I've encountered a problem with some center coordinate computations for the
structured grid images (e.g. the CenteredTransformInitializer). The center
is computed basically as origin + 0.5 * size * spacing in a normally
oriented image. This seems to be contradictory to the image representation,
as the origin is located at the center of the pixel. This is depicted in the
software guide in chapter 4.1.4 "Defining Origin and Spacing.

The formula should use size-1 instead.

For instance, consider an image of size [3,3], pixel spacing [1,1] and zero
origin. In a node centered representation as in ITK, the center position
should be [1,1] instead of [1.5,1.5].

Is this a misunderstanding from my side or is there indeed something wrong
going on?

Thanks,
Dieter

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