Georeference ASCII file in ArcGIS JS web API

[JerryGarcia]

How do I georeference an ASCII file into an ArcGIS JS Web API map?  I know the extent and spatial reference.  I'd like to render the symbology as a red to yellow to green color ramp.  

Thanks!

  // create and add the layer    var mil = new MapImageLayer();    map.addLayer(mil);     // create an add the actual image    var mi = new MapImage({      'extent': { 'xmin': -8864908, 'ymin': 3885443, 'xmax': -8762763, 'ymax': 3976997},      'href': 'http://il.water.usgs.gov/_ags60fb0c9554ef42a58e7024d8464a2ecb.png'    });    mil.addImage(mi);