qgiswms
I have a WMS vector layer added to QGIS desktop.
But the background is not transparent – it is white.
How to change that?
When I add this WMS to ArcGIS – all is just fine.
Here is the WMS link:
http://maps.rosreestr.ru/arcgis/services/Cadastre/CadastreWMS/MapServer/WMSServer?
Some sample results..
Additionally, if you want to make any other color on the raster transparent, You can click the Icon2, This would ask you to select a pixel on the raster using mouse. This might make QGIS go minimized for some weird reason, but you can restore it from the taskbar. Then click the color on the raster which you want to make transparent. It would add a new row for that color and make that color transparent for the raster.
There were a couple of Issues that need to be tackled, before we use the ArcGIS Server's WMS service on top of OpenStreetMaps.
I can use the following code to show he given WMS service on top of OSM layer:
<!DOCTYPE html>
<html>
<head>
<title>OpenLayers Map</title>
<link rel="stylesheet" href="http://openlayers.org/dev/theme/default/style.css" type="text/css">
<link rel="stylesheet" href="http://openlayers.org/dev/examples/style.css" type="text/css">
<script src="http://openlayers.org/dev/OpenLayers.js"></script>
<script type="text/javascript">
var map, layer;
function init(){
map = new OpenLayers.Map('map', {projection: new OpenLayers.Projection("EPSG:3857")});
layer = new OpenLayers.Layer.OSM( "Simple OSM Map");
map.addLayer(layer);
var wmsLayer = new OpenLayers.Layer.WMS( "ArcGIS WMS",
"http://www.webatlasde.de/ArcGIS/services/Maps4BW/MapServer/WMSServer",
{layers: 'Halbtonvariante', FORMAT:"image/png", transparent:"TRUE"},
{isBaseLayer: false});
map.addLayer(wmsLayer);
map.zoomToExtent([807292,6012131,1249140,6277886], true);
}
</script>
<style>
#map{
width:650px;
height:400px;
}
</style>
</head>
<body onload="init()">
<div id="map" ></div>
</body>
</html>
Best Answer
WMS servers can typically serve images in many formats (jpeg, 8-bit png, 24-bit png etc.). Jpeg format, while it gives a good compression rate for natural looking imagery like aerial photos or satellite images, has a drawback that it does not support transparency.
If you need WMS layers with transparency, use png instead of jpeg as an outputformat. For vector layers png is a good choice anyways because such layers can usually be compressed as effectively with png as with jpeg. Png is also a lossless compression method which keeps the lines on the map sharp.