Define footprints (Ellipse/Circle/Polyline/Line) when drawing Catalog/ProgressiveCatalog sources

[bmatthieu3]

This PR has for aim the ability for the user to draw catalogs with a draw function callback that output a footprint. This can be used to draw for example:

• proper motion
• galaxy ellipses

Example:

aladin.addCatalog(A.catalogFromVizieR("VII/237/pgc", "M31", 3, {
        limit: 1000,
        //orderBy: 'nb_ref',
        onClick: 'showTable',
        color: 'yellow',
        hoverColor: 'blue',
        shape: (s) => {
          let coo = A.coo();
          coo.parse(s.data['RAJ2000'] + ' ' + s.data['DEJ2000'])

          let a = (0.1 * Math.pow(10, +s.data.logD25)) / 60;
          let b = (1.0 / Math.pow(10, +s.data.logR25)) * a

          return A.ellipse(coo.lon, coo.lat, a, b, +s.data.PA, {lineWidth: 3});
        }
}));

Output:

What still needs to be done:

• Fix the grid drawing label because I removed the gridCanvas to only have 2 canvas: imageCanvas (webgl) and catalogCanvas (2d). The grid labels are drawn into the catalogCanvas
• Create/adapt the Line class and expose it in the API. Line could have all the option parameter listed here: Visualize proper motion #91
• Enhance the drawing performance (this will be for another PR and may only concern Polyline/Line rendering first).

The PR addresses those issues:

• Visualize proper motion #91
• Setting source size in angular size #14 . With a small extra effort, one can bind the sourceSize given in arcmin to a Footprint
• support STC-S footprints #146 although it is already implemented. When the votable is parsed we look for a s_region labeled column and create footprints from it. But this PR encapsulates the problem which can be rewritten/refac more generically later

[bmatthieu3]

@imbasimba @pmatsson - Here is an example for drawing proper motion over the LMC. These do have been computed from GaiaDR2 with a TAP query returning mean proper motion vectors for all the HEALPix cells on the LMC. The query is the following:

SELECT avg(ra) as ra, avg(dec) as dec, avg(pmra) as pmra, avg(pmdec) as pmdec,
   avg(parallax) as parallax, avg(radial_velocity) as radial_velocity, healpix(ra, dec, 8) AS h
FROM "I/345/gaia2"
WHERE CONTAINS(POINT('ICRS',ra,dec),CIRCLE('ICRS',80.8942,-69.7561,2.5))=1 
   AND sqrt(pmra*pmra+pmdec*pmdec)<30
GROUP BY h

It gives a votable.

And here is the Aladin Lite code snippet that opens that VOTable and define the pm vector over the sources:

let pmraMean = null, pmdecMean = null;
const pmCat = A.catalogFromURL('<my pm votable>', {
  onClick: 'showTable',
  name: 'mean pm over HPX cells around LMC from GaiaDR2',
  hoverColor: 'yellow',
  // Footprint associated to sources
  shape: (s) => {
    // compute the mean of pm over the catalog sources
    if (!pmraMean || !pmdecMean) {
      pmraMean = 0, pmdecMean = 0;
      for (var s of pmCat.getSources()) {
        pmraMean += +s.data.pmra;
        pmdecMean += +s.data.pmdec;
      }

      const numSources = pmCat.getSources().length;

      pmraMean /= numSources
      pmdecMean /= numSources
    }

    let dra = +s.data.pmra - pmraMean;
    let ddec = +s.data.pmdec - pmdecMean;

    let mag = Math.sqrt(dra * dra + ddec * ddec);
    // discard drawing a vector for big pm
    if (mag > 1) {
      return;
    }

    let color = rainbowColorMap(mag * 2)

    return A.line(
      s.ra,
      s.dec,
      s.ra + dra,
      s.dec + ddec,
      null,
      {lineWidth: 3, arrow: true, color}
    )
  }
});
aladin.addCatalog(pmCat);

Result:

Do not hesitate to comment if you have ideas for a generic API, options etc...

[bmatthieu3]

cds-astro/ipyaladin#39