title: What is CIVector's CIAttributeTypeRectangle?
body: <p>I am using Apple's Core Image Filter reference. It references:
  "A CIVector class whose attribute type is CIAttributeTypeRectangle and whose display name is Rectangle."</p>
  
  <p>I can't find anything anywhere that tells me anything about "attribute type is CIAttributeTypeRectangle" and what "display name is Rectangle." means.</p>
  
  <p><a href="http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CoreImageFilterReference/Reference/reference.html#//apple_ref/doc/uid/TP30000136-SW160" rel="nofollow">Apple's docs</a> (look under the CICrop Section)</p>