I have a problem whereby I am seeing a half voxel shift in my millimetre to voxel calculations, and I believe the following example using this mornings build of ExtApp illustrates it.
I have a 3x3 test image with voxel size 2mm x 2mm, and a 5x5 test image with voxel sizes 1mm x 1mm.
The origin for both images should be the centre of the first voxel.
If I load JUST the 3x3 image, the geometry as expected. The first voxel has index 0,0 and millimetre location 0,0.
If I load JUST the 5x5 image, again, it is as expected.
If I load BOTH the 3x3 and the 5x5 I would expect the smaller 5x5 image to be centred symmetrically within the 3x3 image, and this is not the case. It looks like the corners are aligned rather than the centre of the first voxel.
Please find attached my 3x3 image and 5x5 image, and some screenshots.
In the screenshots
first screenshot = 3x3 image = OK
second screenshot = 5x5 image = OK
third screenshot = overlay = PROBLEM????
fourth screenshot = my expectation.
Did I do something wrong, or it my expected behaviour wrong?