<div dir="ltr">According to the VTK convention, you calculation is incorrect. Note that VTK assign each value of an image to a vertex not to a cell. So if the dimensions are {2,2,2} and spacing is {1,1,1}, the bounds of the data will be {0, 1, 0, 1, 0, 1}. So the right way of calculating origin is:<div>

<br></div><div><span style="font-family:arial,sans-serif;font-size:13px">     double origin[3], spacing[3], center[3];</span><br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     int dimensions[3];</span><br style="font-family:arial,sans-serif;font-size:13px">

<br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     imageData->GetOrigin(origin);</span><br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     imageData->GetSpacing(spacing)</span><span style="font-family:arial,sans-serif;font-size:13px">;</span><br style="font-family:arial,sans-serif;font-size:13px">

<span style="font-family:arial,sans-serif;font-size:13px">     imageData->GetDimensions(</span><span style="font-family:arial,sans-serif;font-size:13px">dimensions);</span><br style="font-family:arial,sans-serif;font-size:13px">

<br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     for(int i = 0; i < 3; i++)</span><br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     {</span><br style="font-family:arial,sans-serif;font-size:13px">

<span style="font-family:arial,sans-serif;font-size:13px">         center[i] = origin[i] + ((dimensions[i] - 1 ) * spacing[i]))/2;</span><br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">     }</span><br style="font-family:arial,sans-serif;font-size:13px">

</div><div><span style="font-family:arial,sans-serif;font-size:13px"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:13px">Best,</span></div><div><span style="font-family:arial,sans-serif;font-size:13px">-berk</span></div>

<div><span style="font-family:arial,sans-serif;font-size:13px"><br></span></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Mar 19, 2014 at 7:06 AM, chasank <span dir="ltr"><<a href="mailto:chasank@gmail.com" target="_blank">chasank@gmail.com</a>></span> wrote:<br>

<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
I have a nifti image that has these features below:<br>
<br>
     Dimensions : {301, 370, 316}<br>
     Origin : {75, 107, -69.5}<br>
     Spacing : {0.5, 0.5, 0.5}<br>
<br>
I want to get center world point of the image. When I use GetCenter method<br>
of vtkImageData for this purpose, I get {150, 199.25, 9.25}. However, I<br>
suspected that it seems a bit wrong. And then I tried to calculate the<br>
center point on my own like below:<br>
<br>
     double origin[3], spacing[3], center[3];<br>
     int dimensions[3];<br>
<br>
     imageData->GetOrigin(origin);<br>
     imageData->GetSpacing(spacing);<br>
     imageData->GetDimensions(dimensions);<br>
<br>
     for(int i = 0; i < 3; i++)<br>
     {<br>
         center[i] = origin[i] + ((dimensions[i] / 2) * spacing[i]);<br>
     }<br>
<br>
and center world point becomes {150, 199.5, 9.5}. So which result is true?<br>
My calculation or GetCenter method?<br>
<br>
Best regards.<br>
Chasan<br>
<br>
<br>
<br>
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