You need to use directions (transform matrix) in order to achieve all that.<div><br></div><div>X is the axis 0, Y 1 and Z 2, in image space. In world space they get transformed using the said transform matrix (or directions + spacing).</div>
<div><br></div><div>I am sure you can find much more info if you search for it.</div><div><br></div><div>Regards,</div><div>Dženan<br><br><div class="gmail_quote">On Wed, Dec 15, 2010 at 19:20, David Nichols <span dir="ltr"><<a href="mailto:dnichols@sourcesignal.com">dnichols@sourcesignal.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">My 'natural', image index oriented coordinate system is left handed. I'm thinking that manipulating the itk origin and spacing can put things in the correct order.<br>
<br>
First, it seems that itk uses the C language index order, with the rightmost index changing most quickly. So, if I had an image with 120 slices, each of which had 128 rows and 110 columns, I would declare it in C as<br>
short int Image[120][128][110];<br>
I want to set the origin of the physical coordinate system at voxel [0,0,0], with the x axis pointing in the direction of decreasing row, the y axis pointing in the direction of increasing column and the z axis pointing in the direction of increasing slice. If I look at Image[k][i][j], then increasing x decreases i, increasing y increases j and increasing z increases k.<br>
<br>
Two issues. First, the examples in The Guide seem to assume that x goes with index 0, y with index 1 and z with index 2. How do I permute things to get them as described above? Secondly, to make an advancing row index point in the negative x direction, does one make the spacing negative in that dimension? (This seems logical in one way and perverse in another.) Finally, what would be the correct entries to use in a metaheader file? One can use<br>
<br>
NDims = 3<br>
DimSize = 110 128 120<br>
ElementSize = 1 1 1<br>
<br>
but this doesn't give the x/y/z axes oriented as desired.<br>
<br>
I appreciate any advice you can provide.<br>
<br>
David<br>
<br>
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