<div dir="auto">Thank you, I will give that a try.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Dec 14, 2023, 16:00 F.-X. Pineau <<a href="mailto:francois-xavier.pineau@astro.unistra.fr">francois-xavier.pineau@astro.unistra.fr</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>

  
    
  
  <div>
    <p>What about using MOCPy to:<br>
      1. build a MOC from your Box at a HEALPix resolution near from the
      wanted image pixel resolution<br>
      2. then to compute the intersection of both MOCs<br>
      3. and finally to render the image using the WCS class (see
      <a href="https://cds-astro.github.io/mocpy/stubs/mocpy.WCS.html" target="_blank" rel="noreferrer">https://cds-astro.github.io/mocpy/stubs/mocpy.WCS.html</a>)?<br>
    </p>
    <p>See the MOCPy gallery:<br>
<a href="https://cds-astro.github.io/mocpy/examples/user_documentation.html#gallery-of-notebooks-examples-using-smocs" target="_blank" rel="noreferrer">https://cds-astro.github.io/mocpy/examples/user_documentation.html#gallery-of-notebooks-examples-using-smocs</a><br>
    </p>
    <p><br>
    </p>
    <div>Le 14/12/2023 à 19:43, Arnold Rots a
      écrit :<br>
    </div>
    <blockquote type="cite">
      
      <div dir="ltr">
        <div>On a different note, I have been looking for a tool that
          renders the area covered by the intersection of a Box and a
          MOC.</div>
        <div>Does anyone have something that does that?<br>
        </div>
        <div>Thanks,</div>
        <div><br>
        </div>
        <div>  - Arnold<br>
        </div>
        <div>
          <div>
            <div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">
              <div dir="ltr">
                <div>
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                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(34,34,34);background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Arnold H Rots</span></p>
                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Research Associate</span></p>
                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt">SAO/HEAD</p>
                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Center for Astrophysics | Harvard & Smithsonian</span></p>
                                  <br>
                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(34,34,34);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap"><span><span style="font-size:9.5pt;font-family:Arial;color:rgb(34,34,34);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Email: <a href="mailto:arots@cfa.harvard.edu" target="_blank" rel="noreferrer">arots@cfa.harvard.edu</a></span></span></span></p>
                                  <p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(34,34,34);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Office: +1 617 496 7701 | Cell: +1 617 721 6756</span></p>
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      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">On Wed, Dec 13, 2023 at
          6:49 AM F.-X. Pineau <<a href="mailto:francois-xavier.pineau@astro.unistra.fr" target="_blank" rel="noreferrer">francois-xavier.pineau@astro.unistra.fr</a>>
          wrote:<br>
        </div>
        <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
          <div> <font face="monospace">Dear all,</font><br>
            <br>
            <font face="monospace">Whatever the future of the STC-S
              working draft is, having -- even partial --</font><br>
            <font face="monospace">implementations may help the debate.</font><br>
            <br>
            <font face="monospace">A few MOCPy users have asked for a
              S-MOCs from STC-String feature.</font><br>
            <font face="monospace">And it seems that S-MOCs are
              considered to replace (at least in some places)</font><font face="monospace"> STC.<br>
              I am curious to know where exactly since MOCs and STC-S
              are complementary:</font><br>
            <font face="monospace">* STC-S is compact -- as far as it
              does not contains  unions/intersection of hundreds</font><br>
            <font face="monospace">  of shapes -- and precise, but not
              indexation oriented</font><br>
            <font face="monospace">* MOCs are approximations, not
              compact -- except at low resolutions --</font><br>
            <font face="monospace">  but fast and indexation oriented</font><br>
            <font face="monospace">I believe that efficient STC-S
              queries must rely (internally) on MOCs</font><br>
            <font face="monospace">(or other similar mechanisms), but
              should not be replaced by MOC queries</font><br>
            <font face="monospace">(even if MOC queries are interesting
              too and can help in STC-S queries).</font><br>
            <br>
            <br>
            <font face="monospace">## STC-S Parser</font><br>
            <br>
            <font face="monospace">So, as previously announced, I
              implemented a STC-S parser available on both</font><br>
            <font face="monospace"> github and <a href="http://crates.io" target="_blank" rel="noreferrer">crates.io</a>:</font><br>
            <font face="monospace">* <a href="https://github.com/cds-astro/cds-stc-rust" target="_blank" rel="noreferrer">https://github.com/cds-astro/cds-stc-rust</a></font><br>
            <font face="monospace">* <a href="https://crates.io/crates/stc-s" target="_blank" rel="noreferrer">https://crates.io/crates/stc-s</a></font><br>
            <font face="monospace">There is still room for improvement
              and feeback/comments from people</font><br>
            <font face="monospace">with STC experience would be much
              appreciated.</font><br>
            <br>
            <br>
            <font face="monospace">## STC-S to S-MOC</font><br>
            <br>
            <font face="monospace">This email to announced that I now
              have also implemented a <b>first version of</b></font><b><br>
            </b><font face="monospace"><b>the STC-S to S-MOC feature</b>
              in MOCLibRust and in:</font><br>
            <font face="monospace">* <b>moc-cli</b>: already available
              in pypi and github release</font><br>
            <font face="monospace">    + <a href="https://pypi.org/project/moc-cli/" target="_blank" rel="noreferrer">https://pypi.org/project/moc-cli/</a></font><br>
            <font face="monospace">    + <a href="https://github.com/cds-astro/cds-moc-rust/tree/main/crates/cli" target="_blank" rel="noreferrer">https://github.com/cds-astro/cds-moc-rust/tree/main/crates/cli</a></font><br>
            <font face="monospace">    + Example: echo "Circle ICRS
              147.6 69.9 0.4" | moc from stcs 14 - fits stcs.moc.fits
              --force-u64</font><br>
            <font face="monospace">* moc-wasm: already available in
              github release</font><br>
            <font face="monospace">    + <a href="https://github.com/cds-astro/cds-moc-rust/tree/main/crates/wasm" target="_blank" rel="noreferrer">https://github.com/cds-astro/cds-moc-rust/tree/main/crates/wasm</a></font><br>
            <font face="monospace">* <b>MOCPy</b>: implemented in the
              github source code, but not released yet</font><br>
            <font face="monospace">    +  <a href="https://github.com/cds-astro/mocpy" target="_blank" rel="noreferrer">https://github.com/cds-astro/mocpy</a></font><br>
            <font face="monospace">The feature has been put in place but
              now have to be tested more thoroughly.</font><br>
            <font face="monospace">So far the limitations are:</font><br>
            <font face="monospace">* it <b>supports only frame=ICRS,
                flavor=SPHER2 and units=deg</b></font><br>
            <font face="monospace">* it wrongly considers the<b>
                DIFFERENCE to be a SYMMETRIC DIFFERENCE</b> (XOR)</font><br>
            <font face="monospace">  instead of a "MINUS".</font><br>
            <font face="monospace">  Note that for a single polygon
              whith a hole inside it, the result is the same,</font><br>
            <font face="monospace">  except that:</font><br>
            <font face="monospace">* it does not adopt the STC
              definition of a polygon:</font><br>
            <font face="monospace">  + it <b>supports self-intersecting
                polygons</b></font><br>
            <font face="monospace">  + the polygon interior is (kind of)
              the part having the smallest area, i.e.</font><br>
            <font face="monospace">    the order of the vertices does
              not matter</font><br>
            <font face="monospace">We do support nested
              UNION/NOT/INTERSECTION/XOR operations.</font><br>
            <font face="monospace">To do so, we rely on BMOCs
              implemented in the CDS HEALPix Rust library.     </font><br>
            <font face="monospace">BMOCs are S-MOCs storing in each cell
              a boolean flag telling if the cell is for </font><br>
            <font face="monospace">sure fully inside the geometrical
              shape or not.</font><br>
            <font face="monospace">For example, the NOT operation
              removes all cells having the boolean set to 'true'</font><br>
            <font face="monospace">but preserves the cells having the
              boolean set to 'false' (and add missing cells</font><br>
            <font face="monospace">setting their flag to 'true').</font><br>
            <font face="monospace">BMOCs have so far two drawback:</font><br>
            <font face="monospace">* operations on BMOCs has not yet
              been thoroughly tested</font><br>
            <font face="monospace">* operations on BMOCs are -- at least
              in the current implementation -- much slower </font><br>
            <font face="monospace">  than operations on MOCs</font><br>
            <font face="monospace">In the future, we may first detect
              the operations in a STC-String to switch</font><br>
            <font face="monospace">between MOCs (neither NOT or
              DIFFERENCE operations) and BMOCs.</font><br>
            <font face="monospace">Except that BMOCs have also one big
              advantage: they can be spitted into 2 sub-MOCs</font><br>
            <font face="monospace">* one fully inside the STC region (no
              additional test needed, e.g. when retrieving sources)</font><br>
            <font face="monospace">* one "edges" MOC: additional tests
              needed to determine if a source in this MOC</font><font face="monospace"><br>
                is in or out of the STC region.</font><br>
            <font face="monospace"><br>
              <b>If you have example of STC-String, especially with
                operations (Alberto?),     <br>
                please send them to us so we can add them to our tests.</b><br>
              <br>
              Even if STC-S is dropped in the future, it should not be
              that complex to<br>
              adapt to another standard like DALI "shape".<br>
              (Although STC-S is complex, it is quite complete and
              self-consistent since it contains<br>
              information such as the frame: the two sides of a medal).<br>
              <br>
              <br>
              ## About polygons:<br>
              <br>
              We support self-intersecting polygons.<br>
              <br>
              Although it is useless when describing footprints, I do
              think it makes sense<br>
              when you let a user create a polygon by clicking in
              interfaces such as<br>
              Aladin/Aladin Lite or TOPCAT.<br>
              In addition, the existing algorithm to deal with
              self-intersecting polygons is<br>
              simple (at least in the plane, with some complications on
              the sphere)<br>
              and fast (see <a href="https://wrfranklin.org/Research/Short_Notes/pnpoly.html" target="_blank" rel="noreferrer">https://wrfranklin.org/Research/Short_Notes/pnpoly.html</a>).<br>
              <br>
              The best option to define the interior/exterior of a
              self-intersecting polygon<br>
               may be to provide a control point, provided it is not a
              vertex and is not part<br>
              of an edge. (It's on of the several options that has been
              implemented in the<br>
               CDS Healpix Lib).<br>
              The control point can be automatically computed from the
              current standard for<br>
              non-intersecting polygons:<br>
              * for convex polygons: we can use the gravity center (or
              its opposite) by testing it<br>
                with the current convention (if the gravity center is
              (0, 0, 0),<br>
                remove recursively one vertex, starting from the first
              one).<br>
              * concave polygons: by testing the gravity center of 3
              successive non-aligned vertices,<br>
                iterating till one lies inside the polygon by the
              current standard (also ensuring<br>
                the point is not a vertex or on an edge).<br>
              * self-intersecting: the control point would have to be
              provided, i.e. after the last<br>
                vertex (unless we all agree on a same algorithm, using
              the NOT operation to define<br>
                the complement polygon).<br>
              <br>
              Alberto:<br>
              If I understand correctly, a polygon with a hole is the
              intersection<br>
              of a CCW polygon with a (smaller) CW polygon, right?<br>
              Why not having used the difference between two CCW
              polygons?<br>
              Is it because the difference in STC-S is not a symmetric
              difference and hence<br>
              you cannot use the logical XOR operation in a database
              expression?<br>
              (<b>That may advocate to replace the DIFFERENCE by/ or at
                least to add a<br>
                 SYMMETRIC DIFFERENCE in STC :)</b> ).<br>
              <br>
              <br>
              fx<br>
              <br>
              <br>
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