[Gdal-dev] JP2ECW ColorTables

[Ivan Lucena]

Dave,

 

I think it's a limitation of JPEG. It can't handle a color table at all.
You can check the free Intel or Microsoft implementation, but I guess
that JPEG wasn't designed for it or the compression algorithm does not
work with color table (now I am stretching my luck ;-)

 

I had the same problem and Frank advised me to look at the Python script
"pct2rgb.py" in the GDAL /bin folder to see how it creates a temporary
RGB GeoTiff and then translate it to JPEG. The advantage that I've found
in this technique is that it also allow you to convert input data types
other them byte to JPEG. You just need to normalize the values in 0-255
and use it as an color index.

 

I've implemented it in Delphi (+ GDAL) and its working fine.

 

Lucena, Ivan

 

________________________________

From: gdal-dev-bounces at lists.maptools.org
[mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of Murphy, David
Sent: Tuesday, June 06, 2006 11:28 AM
To: gdal-dev at lists.maptools.org
Subject: [Gdal-dev] JP2ECW ColorTables

 

Hello-

 

Is there a GDAL create option to enable the JP2ECW driver to handle
color tables?  Our goal is to translate 1-band HFA (*.img) files with a
color table to JP2ECW files, but it seems that the JP2ECW driver
defaults all 1-band files to greyscale.  Any info would help.

 

Thanks,

Dave Murphy

 

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