Added support for images in "png" format to the WMTS (Web Map Tile Service) sensor

We have added to the sensor Web Map Tile Service (WMTS) the possibility of loading images .png so that now the sensor is compatible with all those WMTS servers that only provide images in that format, such as the one provided by the Spatial Data Infrastructure of Andalusia. As a result, the dialog box Parameters to connection to Web Map Tile Service has been modified and now shows a drop-down that allows us to select the type of image to request from the server. The .png file format compresses without loss, and its compression ratio is very good but only for synthetic images. In the case of photographs (such as an orthophoto) its compression ratio is much worse than the jpeg, so we recommend that you select png if you are connecting to a WMTS server that provides synthetic images such as a street map or a thematic map. If on the other hand you are downloading orthophotos and the server allows you to select jpeg, select jpeg to consume less bandwidth and the images appear faster in the Digi3D.NET window. Below is a screenshot obtained from the orthophoto server: WMS-C Service of Orthophotography 2010-2011 using the following connection string:

Server=http://www.ideandalucia.es/geowebcache/service/wmts?Request=GetCapabilities;Layer=orto_2010-11_23030;Style=_null;ImageFormat=image/png;TileMatrixSet=IDEAvisor:23030