Unfortunately, the space occupied by a pixel was not defined early enough in ITK development. In about half the circumstances, it is assumed that the coordinate of a pixel is associated with the center of the pixel. In the other half, it is assumed that the coordinate of a pixel is associated with a corner of the pixel.
<br><br>itk::Image::TransformIndexToPhysicalPoint() is alright regardless of the interpretation but itk::Image::TransformPhysicalPointToIndex() pretty much assumes a pixel's coordinate is defined by one of its corners.
<br><br>Some of the ImageFunction classes take care of this 1/2 pixel shift automatically.<br><br>But there are other places in the code where an implicit assumption is made on the coordinate frame. These are hard to identify.
<br><br>ITK as designed to handle negative indices, but as Karthik mentions, there may be code where it implicitly assumes positive or unsigned indices.<br><br>An image with unity spacing an 100 pixels in a dimension <span style="font-style: italic;">
should</span> have been defined to cover the space [-0.5, 99.5). At some point, we'll bite the bullet and fix this.<br><br>Jim<br><br><div><span class="gmail_quote">On 12/22/06, <b class="gmail_sendername">Emmanuel Christophe
</b> <<a href="mailto:melaneum@gmail.com">melaneum@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hello,<br>
<br>What is the valid range for a continous index of a dataset of size 100<br>starting at 0 ?<br><br>Index (integer) will be going from 0 to 99 (included).<br>I would expect the continuous index to be valid from [0,100[ (100
<br>excluded but 99.9 included for example)<br><br>Apparently the IsInside function consider the continousIndex to be<br>inside only if in the interval [0,99] (99.9 excluded for example). Is<br>there a reason for such a choice ?
<br><br>Thanks,<br>Emmanuel Christophe<br>_______________________________________________<br>Insight-users mailing list<br><a href="mailto:Insight-users@itk.org">Insight-users@itk.org</a><br><a href="http://www.itk.org/mailman/listinfo/insight-users">
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