WCS does not handle OFFSITE/NODATA through tileindex

[jratike80]

WCS server does not handle correctly warped images which contain nodata areas if they are used through tileindex. Nodata areas are not treated as transparent but the WCS output has also the nodata pixels burned into image with they original pixel values, in my case totally black, RGB 0 0 0. This happens even if gdalinfo correctly reports the nodata values for each image in the tileindex mosaic, and in the mapfile, in LAYER section there is a row OFFSITE 0 0 0. The same layer gives seamless result when used though Mapserver WMS.

WCS creates correct images if .vrt file is used instead of shapefile tileindex. Changes which I needed were

• Convert shapefile tileindex into .vrt with gdalbuildvrt from FWTools 2.4.2 package. No parameters were needed, it was enough to give a command simply as > gdalbuildvrt M085_WMS.vrt m085_wms.shp
• Edit a mapfile to read this .vrt file instead of tileindex

#TILEINDEX "d:/data/M085_WMS" DATA "d:/data/M085_WMS.vrt"