[OpenLayers-Users] How to calculate Bounds for Image Layer Example?

[Jan Martin]

Hi all,

I am working from the Image Layer Example:
http://openlayers.org/dev/examples/image-layer.html

Goal is to switch to an image layer showing a picture (e.g. of a Church).
I managed to switch from the original map to the image layer using
map.setBaseLayer(image-layer);

Problem is how to calculate OpenLayers.Bounds?
Simply replacing
   new OpenLayers.Bounds(-180, -88.759, 180, 88.759),
by
  new OpenLayers.Bounds(-20037508, -20037508, 20037508, 20037508.34)
did not work.
(It just blows up a single pixel to cover the whole map-div.)

And even when the example states:
..."If you construct it without any resolution related options [Does this
mean Bounds???], the layer will be given a single resolution based on the
extent/size."...
Commenting out the "new OpenLayers.Bounds( ..." line does not work, it just
gives an error in both OL 2.7 and 2.8:

this.extent.getHeight is not a function
http://localhost/js/OpenLayers.js
Line 1187

So how to calculate OpenLayers.Bounds to display the image at its
original 100% size?

Or to fit in the map-div?

Thanks,
Jan


Image Layer Example Code (Cleaned up a bit):

<script type="text/javascript">

        var map;
        function init(){
            map = new OpenLayers.Map('map');

            var options = {numZoomLevels: 3};

            var graphic = new OpenLayers.Layer.Image(
                'City Lights',

                'http://earthtrends.wri.org/images/maps/4_m_citylights_lg.gif',
                new OpenLayers.Bounds(-180, -88.759, 180, 88.759),

                new OpenLayers.Size(580, 288),
                options
            );

            var jpl_wms = new OpenLayers.Layer.WMS( "NASA Global Mosaic",
                "http://t1.hypercube.telascience.org/cgi-bin/landsat7",

                {layers: "landsat7"}, options);

            map.addLayers([graphic, jpl_wms]);
            map.addControl(new OpenLayers.Control.LayerSwitcher());
            map.zoomToMaxExtent();

        }
    </script>
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