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MINC 2 defines both ``voxel'' and ``world'' spatial coordinate systems.
For each dimension, the world coordinate conversion is specified
by a pair of attributes: step and start. The xspace world coordinate,
for example is calculated using x = v*step + start, where x is the x world
coordinate and v is the voxel count (starting at zero). Thus the magnitude
of the step attribute specifies the distance between voxels and the sign
of the step attribute specifies the orientation of the axis. MINC files are
allowed to have non-orthogonal axes with the dimensions not perfectly
aligned with the named axis. There can be a direction_cosine attribute that
gives the true orientation of the axis. For example, normally the xspace
dimension should line up with the world x axis, ie. direction cosine = (1,0,0)
; however, it is possible to have a direction cosine of (0.9, 0.43589, 0).
For detailed formulas please refer to APPENDIX A, section 2.1
The MINC 2.0 File Format by Robert D. Vincent.
Next: Coding Examples
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Robert VINCENT
2004-05-28