Hello, How about adding alpha channel to your Sounds like having alpha channel might be perfect fora place to try adding alpha channel to your GeoTIFFs? I suppose that can be done with gdalwarp, at least it is having a switch -dstalpha. However, the user documentation at http://www.gdal.org/gdalwarp.html is saying nothing about that switch. Regards, Jukka Rahkonen
________________________________ Lähettäjä: UMN MapServer Users List puolesta: Kirk Holbrook Lähetetty: ke 12.4.2006 23:33 Vastaanottaja: [email protected] Aihe: [UMN_MAPSERVER-USERS] GeoTIFF source alpha/transparency: what's the best method? Hi, I've been working to optimize my map that uses several large geoTIFFs (over 500MB each). I started out using Red (RGB 255 0 0) as the area to be transparent in my TIFFs (since there is no true red in any of my TIFFs) and using "OFFSITE 255 0 0" in each layer to make it transparent. It works well, but when I use gdaladdo to add overviews to optimize my map, I get a lot of red artifacts in the overviews. I've also set up a tileindex which is helping immensely. Is there a better way to handle transparency? I've got 24 bit TIFFs (which I'd like to keep, rather than going to 8 bit). Note also that my transparent areas are not necessarily rectangular -- there are a few odd shapes. Thanks a lot, Kirk
