You first have to make sure you are outputting the image as a png or some other image format that supports transparency. Like this, at the base of the mapfile:
OUTPUTFORMAT NAME mypng DRIVER "GD/PNG" IMAGEMODE RGB FORMATOPTION "INTERLACE=false" MIMETYPE "image/png" EXTENSION "png" END IMAGETYPE mypng Then, if your source image is not perfectly square, and has black in areas that you want to be transparent, you can use the "OFFSITE [R] [G] [B]" attribute. This tells mapserver that any color in the raster that matches the color in your OFFSITE parameter should be rendered transparent. ex: LAYER NAME "blah" DATA '/path/to/raster.tiff' OFFSITE 0 0 0 END This has worked for me in the past, I hope it works for you. -Matt Mendick -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/quick-question-from-mapserver-beginner-tp5040040p5040856.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