[Insight-users] Image to world coordinates

[Vincent Garcia]

Hi all,

When you read a medical image (let's say 3D), you have a 3D matrix 
containing image data and some information about the 
position/orientation of the image in the world coordinates. Given the 
image coordinates (i,j,k), I'd like to understand how to compute the 
corresponding world coordinates (x,y,z).
I have access to some information from the itk::Image object:

GetOrigin () : (vector) position of the first voxel in the world coordinates
GetSpacing () : (vector) size of the voxels in mm
GetDirection () : (matrix) direction cosine

I've tried to search on the documentation but I haven't found the way to 
use these vectors and matrix to compute the world coordinates.
The formula should be very simple but I just can't found it.

Many thanks,

Vincent Garcia