Converting Geotiff Image Files from 24 bit color to 8 bit.
Note : OziExplorer can read both 24 bit and 8 bit tif images and both formats are paged in as required.
If a 24 bit image is converted to 8 bit color the Geotiff georeference information is lost.
This document describes a technique to save the georeference information and to then put it back into the file.
Software to convert the Geotiff image from 24 bit to 8 bit color. Paint Shop Pro (www.jasc.com) works well.
The Tiff Utilities available from the Utilities section of the OziExplorer web site (www.oziexplorer.com).
These instructions assume the geotiff file you are converting is called mytiff.tif and is located in a folder called c:\images, replace this with the real name of the tif file and path.
Open a DOS window.
Use the listgeo.exe program to save the georeference information from the geotiff file into a file called mytiff.met, actually this file can have any name.
listgeo c:\images\mytiff.tif >c:\images\mytiff.met
Convert the image to 8 bit color using Paint Shop Pro, the image is saved to mytiff1.tif, the compression method must be packbits and this is set up in the options button on the save dialog.
Use the geotifcp.exe program to put the georeference information back into the file.
geotifcp -g c:\images\mytiff.met c:\images\mytiff1.tif c:\images\mytiff2.tif