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diff --git a/funtools/doc/regdiff.html b/funtools/doc/regdiff.html new file mode 100644 index 0000000..29c9658 --- /dev/null +++ b/funtools/doc/regdiff.html @@ -0,0 +1,71 @@ +<!-- =defdoc regdiff regdiff n --> +<HTML> +<HEAD> +<TITLE>Differences Between Funtools and IRAF Regions</TITLE> +</HEAD> +<BODY> + +<!-- =section regdiff NAME --> +<H2><A NAME="regdiff">RegDiff:Differences Between Funtools and IRAF Regions</A></H2> + +<!-- =section regdiff SYNOPSIS --> +<H2>Summary</H2> +Describes the differences between Funtools/ds9 regions and the old IRAF/PROS +regions. + +<!-- =section regdiff DESCRIPTION --> +<H2>Description</H2> +<P> +We have tried to make Funtools regions compatible with their +predecessor, IRAF/PROS regions. For simple regions and simple boolean +algebra between regions, there should be no difference between the two +implementations. The following is a list of differences and +incompatibilities between the two: + +<UL> + +<P> +<LI>If a pixel is covered by two different regions expressions, +Funtools assigns the mask value of the <B>first</B> region that +contains that pixel. That is, successive regions <B>do not</b> +overwrite previous regions in the mask, as was the case with the +original PROS regions. This means that one must define overlapping +regions in the reverse order in which they were defined in PROS. If +region N is fully contained within region M, then N should be defined +<B>before</B> M, or else it will be "covered up" by the latter. This +change is necessitated by the use of optimized filter compilation, i.e., +Funtools only tests individual regions until a proper match is made. + +<P> +<LI> The <B>PANDA</B> region has replaced the old PROS syntax in which +a <B>PIE</B> accelerator was combined with an <B>ANNULUS</B> accelerator +using <B>AND</B>. That is, +<PRE> + ANNULUS(20,20,0,15,n=4) & PIE(20,20,0,360,n=3) +</PRE> +has been replaced by: +<PRE> + PANDA(20,20,0,360,3,0,15,4) +</PRE> +The PROS syntax was inconsistent with the meaning of the <B>AND</B> operator. + +<P> +<LI> The meaning of pure numbers (i.e., without format specifiers) in +regions has been clarified, as has the syntax for specifying coordinate +systems. See the general discussion on +<A HREF="./regions.html">Spatial Region Filtering</A> +for more information. + +</UL> + +<!-- =section regdiff SEE ALSO --> +<!-- =text See funtools(n) for a list of Funtools help pages --> +<!-- =stop --> + +<P> +<A HREF="./help.html">Go to Funtools Help Index</A> + +<H5>Last updated: November 16, 2005</H5> + +</BODY> +</HTML> |