Using an PNG or JPEG for Map with OpenLayers (Scale/Zoom Problem)

Question

I am using an image to display my map with OpenLayers. My JS code looks like this:

map = new OpenLayers.Map('map');

var options = {numZoomLevels: 7,
                isBaseLayer: true,
                };

var globe = new OpenLayers.Layer.Image(
    'Globe ESA',
    'http://upload.wikimedia.org/wikipedia/commons/0/07/World_map_blank_black_lines_4500px.gif',
    new OpenLayers.Bounds(-180, -90, 180, 90),
    new OpenLayers.Size(4500, 2234),
    options);

map.addLayers(globe);

markers = new OpenLayers.Layer.Markers("markers");
map.addLayer(markers);

map.addControl(new OpenLayers.Control.LayerSwitcher());
map.zoomToMaxExtent();
map.addControl(new OpenLayers.Control.MousePosition());

My CSS is:

#map {
    width: 640px;
    height: 480px;
    border: 1px solid black;
}

But I can't get OpenLayers to scale down the large image. It is always display at full resolution and I can't zoom out to display the whole globe. Help please.

Answer 1

You need to set the size of the image as it should display when fully zoomed out.

var globe = new OpenLayers.Layer.Image(
    'Globe ESA',
    'http://upload.wikimedia.org/wikipedia/commonS/0/07/World_map_blank_black_lines_4500px.gif',
    new OpenLayers.Bounds(-180, -90, 180, 90),
    new OpenLayers.Size(1125,558),
    options);

I changed the size to one fourth of the size of the original. You could make this smaller if you wanted it even more zoomed out.