Best GeoTIFF format for GM

Hefy_jefyHefy_jefy Global Mapper UserPosts: 1
edited May 2013 in Raster Data
Hello,
I am not a Global Mapper user but we have a customer that takes GeoTIFF tiles from our GIS application and imports them into Global Mapper to create larger GeoTIFFs. The question has come up recently regarding the best method to handle transparency. The output TIFF type from our application is 24bit LZW compression with optionally an Alpha channel for transparency - I gather that GM also has the ability to assign a specific color as transparent. Since our app can export with any background color this would also be a solution.

Be grateful for any advice.
Geoff

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2013
    Geoff,

    You can set one or more colors transparent for a GeoTIFF layer on the Options dialog for the layer. When you save a new GeoTIFF with transparency though the valid/invalid flag always comes in the form of an alpha channel. GeoTIFF doesn't have a special transparency mode where just a single color is marked as invalid in the file like PNG does for palette-based images. If you create a compressed GeoTIFF that alpha channel will typically compress down into almost no space though, so there isn't much cost to it.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
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