1regdiff(n)                    SAORD Documentation                   regdiff(n)
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NAME

6       RegDiff:Differences Between Funtools and IRAF Regions
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SYNOPSIS

9       Describes the differences between Funtools/ds9 regions and the old
10       IRAF/PROS regions.
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DESCRIPTION

13       We have tried to make Funtools regions compatible with their predeces‐
14       sor, IRAF/PROS regions. For simple regions and simple boolean algebra
15       between regions, there should be no difference between the two imple‐
16       mentations.  The following is a list of differences and incompatibili‐
17       ties between the two:
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19       ·   If a pixel is covered by two different regions expressions, Fun‐
20           tools assigns the mask value of the first region that contains that
21           pixel.  That is, successive regions do not overwrite previous
22           regions in the mask, as was the case with the original PROS
23           regions.  This means that one must define overlapping regions in
24           the reverse order in which they were defined in PROS.  If region N
25           is fully contained within region M, then N should be defined before
26           M, or else it will be "covered up" by the latter. This change is
27           necessitated by the use of optimized filter compilation, i.e., Fun‐
28           tools only tests individual regions until a proper match is made.
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30       ·   The PANDA region has replaced the old PROS syntax in which a PIE
31           accelerator was combined with an ANNULUS accelerator using AND.
32           That is,
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34             ANNULUS(20,20,0,15,n=4) & PIE(20,20,0,360,n=3)
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36           has been replaced by:
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38             PANDA(20,20,0,360,3,0,15,4)
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40           The PROS syntax was inconsistent with the meaning of the AND opera‐
41           tor.
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43       ·   The meaning of pure numbers (i.e., without format specifiers) in
44           regions has been clarified, as has the syntax for specifying coor‐
45           dinate systems. See the general discussion on Spatial Region Fil‐
46           tering for more information.
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SEE ALSO

49       See funtools(n) for a list of Funtools help pages
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53version 1.4.0                   August 15, 2007                     regdiff(n)
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