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Exporting Color Index from TIFF/IMG

QiaoQiao Global Mapper UserPosts: 74Trusted User
edited February 2011 in Raster Data
Hi Mike,

I have a raster data in TIFF or IMG format. When loaded in Global Mapper, it is automatically treated as color imagery although I believe that only unsigned 8-bits numbers are stored in the file. Moving cursor, you could see the Pal Idx numbers, which are the numbers I interested in. I am wondering whether we could export the image to BIL file with the color indices values (i.e., Pal Idx) as unsigned 8-bits. I tried both "BIL - RGB" and "BIL - Grayscale". Neither one give me the original numbers.

Thanks,

Qiao

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited February 2011
    Qiao,

    It sounds like your images are 8-bit palette based images, so the colors that you are seeing are from the palette that converts the 8-bit value to a 24-bit color. What you can do is edit the palette of the image on the Palette tab of the Options dialog to use a grayscale value value each entry (i.e. RGB(0,0,0) for 0, RGB(1,1,1) for 1, etc.), then when you export to say a BIL - grayscale image you would get the original palette indices as the grayscale values in the output file.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • QiaoQiao Global Mapper User Posts: 74Trusted User
    edited February 2011
    Hi Mike,

    Your suggested approach worked well. Thanks for your help!

    All the best,

    Qiao
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