Dear Frank, dear all, thanks for your reply. I think I have narrowed down the problem and it isn't really a mapserver issue - the 8bit paletted img gets rendered to a 4bit-per-pixel png whereas the correctly transparent RGB img gets rendered to an 8bit-per-pixel png. Seems that the Google Earth API can't detect/deal with the NoData value in this 4bpp png and renders this value sort of "shaded black" (which I would like to get ridd of). GIMP for example can deal with the transparency in this 4bpp png.
If I switch to RGBA in the output format, then I have the transparency however the image is much bigger: OUTPUTFORMAT NAME png DRIVER "GD/PNG" MIMETYPE "image/png" # IMAGEMODE RGBA IMAGEMODE PC256 EXTENSION "png" TRANSPARENT ON FORMATOPTION "transparent=on" END Is there a way I can force the mapserver to produce 8bpp pngs? THANKS for your help - highly appreciated - and greetings, Chris PS here's the gdalinfo output for the 4bpp png: Driver: PNG/Portable Network Graphics Files: lb_usa.png Size is 1024, 768 Coordinate System is `' Corner Coordinates: Upper Left ( 0.0, 0.0) Lower Left ( 0.0, 768.0) Upper Right ( 1024.0, 0.0) Lower Right ( 1024.0, 768.0) Center ( 512.0, 384.0) Band 1 Block=1024x1 Type=Byte, ColorInterp=Palette NoData Value=0 Image Structure Metadata: NBITS=4 Color Table (RGB with 9 entries) 0: 1,1,1,0 1: 0,0,0,255 2: 12,16,120,255 3: 31,62,140,255 4: 33,110,158,255 5: 42,156,154,255 6: 61,184,104,255 7: 59,214,45,255 8: 113,235,47,255 -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/NoDATA-value-transparency-for-paletted-IMG-file-tp6305135p6312790.html Sent from the Mapserver - User mailing list archive at Nabble.com. _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users