VisiOmatic set-up and customizationΒΆ

Let us now describe the HTML and JavaScript code that make up a typical VisiOmatic-based web client. We will assume that the IIPImage-astro FCGI is already up and ready to serve pixel data on the server (see Server installation and configuration).

The VisiOmatic web client [1] works essentially as a large Leaflet plug-in, providing subproperties to the original Leaflet “classes” with new or overloaded methods. The whole client fits in a single HTML file. The relevant part of the HTML file begins with the inclusion of the Leaflet, jqPlot, Spectrum and VisiOmatic Cascading Style Sheets in the HTML header:

<!DOCTYPE html>
<html lang="en">
  <meta charset='utf-8' name='viewport' content='width=device-width,
        initial-scale=1.0, maximum-scale=1.0, user-scalable=no'>
  <link rel='stylesheet' href='visiomatic/dist/jqplot.css' />
  <link rel='stylesheet' href='visiomatic/dist/spectrum.css' />
  <link rel='stylesheet' href='Leaflet/dist/leaflet.css' />
  <link rel='stylesheet' href='visiomatic/dist/visiomatic.css' />

The Leaflet map itself may be styled (background color, dimensions):

<style type='text/css'>
  body {padding: 0; margin: 0; }
  html,body,#map { width: 100%; height: 100%; }

The following Javascript library files must be included: jQuery (V2.1.4+), jqPlot (V1.0.8+), Spectrum (V1.7.1+), Leaflet (V1.0) and VisiOmatic (V2.0+). Custom Catalog objects may be included too.

  <script src='visiomatic/dist/jquery-min.js'></script>
  <script src='visiomatic/dist/jqplot-min.js'></script>
  <script src='visiomatic/dist/spectrum-min.js'></script>
  <script src='Leaflet/dist/leaflet.js'></script>
  <script src='visiomatic/dist/visiomatic.js'></script>
  <script src='catalogs.custom.js'></script>

The whole Leaflet/VisiOmatic interface, including advanced menus, fits in a <div> HTML element. The element can be styled to occupy the whole HTML body (as in this dedicated viewer example), or a smaller section of an existing web page. There can be several independent viewing areas (“maps”) per web page; each of them must have a different id attribute. The map below is given a black background.

  <div id='map' style='background:black'></div>

Next comes the JavaScript code. The first thing it does is to capture the URL of the web page. The L.IIPUtils.parseURL() utility function (see description in next chapter) parses it to generate a dictionary of query string keyword/value pairs that we will use to modify specific viewer settings:

  var args =  L.IIPUtils.parseURL(;

For instance, if the current webpage URL is, args['foo'] will contain 'ok' and args['bar'] will contain '1'.

The command initializes the map inside the HTML element that carries the given id ('map' in this example):

var map ='map', {fullscreenControl: true, zoom: 5});

Note the fullscreenControl option (false by default) that adds a Full-Screen switch to the regular Leaflet interface.

The heart of the viewer code is the instantiation and initialization of the image layer with L.tileLayer.iip() (see next chapter). L.tileLayer.iip() accepts a query string comprised of the FastCGI URL and the name of the data file, plus a set of options:

var iip = '/fcgi-bin/iipsrv.fcgi?FIF=cfhtls_d1.ptif',
    layer = L.tileLayer.iip(iip, {
  center: args['center'] ? args['center'] : false,
  fov: args['fov'] ? parseFloat(args['fov']) : false,
  mixingMode: args['mode'] ? args['mode'] : 'color',
  defaultChannel: args['channel'] ?
    parseInt(args['channel'], 10) : 2,
  contrast: 0.7,
  gamma: 2.8,
  colorSat: 2.0,
  channelColors: [[0,0,1],[0,1,1],[0,1,0],[1,1,0],[1,0,0]],
  channelLabels: [
    'u band',
    'g band',
    'r band',
    'i band',
    'z band'

The example above illustrates some options including

  • using query arguments in the URL of the present web page to set the initial center coordinates, zoom level, mixing mode and monochromatic channel index for the viewer,
  • changing the default image contrast, gamma factor and color saturation,
  • applying colors to the different channels (channelColors),
  • labeling every image channel (channelLabels).

The rest of the code instantiates controls that will help the user interact with the data. First of all, a map scale in angular units (pixel units are turned off), a central reticle, and the coordinate input/output widget are set up:

L.control.scale.wcs({pixels: false}).addTo(map);

var wcsControl = L.control.wcs({
  coordinates: [{label: 'RA,Dec', units: 'HMS'}],
  position: 'topright'

Next a “navigation map” is added, using L.control.extraMap(). The navigation map is synchronized with the main map. The tile layer object in the navigation map must be distinct from that of the main map, even if it deals with the same data-cube, as here. For displaying the navigation layer we select only channels #2,#3 and #4:

var navlayer = L.tileLayer.iip(iip, {
  channelColors: [,[0,0,1],[0,1,0],[1,0,0],],

var navmap = L.control.extraMap(navlayer, {
  position: 'topright',
  width: 128,
  height: 128,
  zoomLevelOffset: -6,
  nativeCelsys: true,

We now initialize a side-bar that will regroup all advanced controls, and set up the channel mixing controls and the image settings controls:

var sidebar = L.control.sidebar().addTo(map);;

The L.control.iip.catalog() command adds a catalogue overlay selection menu to the interface. The list of catalogues below is comprised of the 2MASS [2], SDSS [3], and Hudelot et al. [4] catalogues (the latter is defined in catalogs.custom.js):


Regions/Points Of Interest are managed through a very similar interface; using region objects in place of catalog objects. In our example the objects’ content is assigned right in the call to L.control.iip.region():

      url: 'observation_footprint.json',
      name: 'observation footprint',
      description: 'Footprint of the optical observations',
      color: 'blue',
      load: false
      url: 'poi.json',
      name: 'Molinari+ 2011 POIs',
      description: 'Points of Interest discussed in Einstein et al. 2016',
      color: 'orange',
      load: false
  { nativeCelsys: true }

L.control.iip.profile() adds a measurement tab:


Finally, L.control.iip.doc() can be invoked to add an online documentation tab. Any website may be displayed in the documentation panel; it is sand-boxed inside an HTML iframe element. Additionally, a URL to a PDF file may be provided, making a “Download PDF” button pop up in the interface.

    L.control.iip.doc('doc/index.html', {
      pdflink: 'doc/doc.pdf'

Note the call to sidebar.addTabList() which moves the next tab to the bottom of the side bar.