TIFF/GeoTIFF images on MapServer 3.2

Pericles S. Nacionales pnaciona at lists.gis.umn.edu
Sat May 1 13:42:29 PDT 1999


Thanks, folks for your help on my TIFF/GeoTIFF problem.  Thanks specially to
Ken Boss.

> You can do the color reduction in Imagine using the
> Interpreter->Utilities->Adv. RGB Clustering menu option.  (You can try
> to RGB Clustering option above it, but in my experience the results
> are generally unacceptable).  Select your input image, choose the
> three bands you want to work with, and hit the "Load Image Data"
> button.  Then go to the "Partition Data" tab and tweak the "(Color)
> Sections" values, hitting the "Calculate Number of Classes" button
> with each change.  Ideally, you'll want a number of classes
> approaching, but not exceeding, 256 (and a data type of Unsigned 8
> bit).  Usually some combination of 7s and 8s in the Color Sections
> will get you there.  I've never tried the threshold options, you may
> want to experiment with those as well.
>
> Once you've got the parameters set where you want them, click the
> Build LUT button.  Then go back to the Image I/O tab, specify your
> output image, and hit the "Produce Output" button.  You'll get a new,
> single-band .img file that you can then convert to GeoTIFF.
>
> The results are generally pretty good, but the process is a bit
> unwieldy and doesn't lend itself to automated processing of large
> numbers of images.  We use a product called "Image Alchemy"
> (http://www.handmadesw.com/) for such purposes - it reads (but doesn't
> write) .img files and will output to a huge variety of image formats,
> including TIFF.  I don't think it does GeoTIFF, though as Steve points
> out you can just concoct an ESRI world file in that case.  Of course
> there are plenty of other packages that could be used as well, but I
> don't know of any others off-hand that can read .img files, if that's
> an issue.




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