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I am using a GeoExt.LegendPanel to show legends for my various layers in OpenLayers. The GeoExt.WMSLegend supports configuring which image format to use, but the LegendPanel does not utilize this causing the WMSLegend to fallback to image/gif.

So far I have manually edited the GeoExt.js minified file to make the WMSLegend use image/png as default instead of image/gif, but I would prefer to parameterize this.

Am I missing some way to configure my LegendPanel to use image/png as my WMSLegend image format?

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up vote 3 down vote accepted

You should use a following way:

var legendPanel = new GeoExt.LegendPanel({
    map: map,
    defaults: {
        showTitle: false,
        baseParams: {
            FORMAT: 'image/png'
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