[Gdal-dev] Conversion of paletted PNG to ECW does not work
Frank Warmerdam
warmerdam at pobox.com
Tue Dec 19 20:27:33 EST 2006
Jean-Claude Repetto wrote:
> Hello,
>
> When I convert a paletted PNG file to ECW, the resulting image is almost
> black, as if the compression was made using the indexes instead of the
> real colours.
>
> I am using GDAL 1.3.2 on Gentoo-64.
> Example:
> gdal_translate -of ECW -co "TARGET=94%" -co "DATUM=NTF" -co
> "PROJ=LM1FRA2D" -a_ullr a_ullr 970000 1860000 980000 1850000 test.png
> test.ecw
>
> There is no problem with a true colour PNG image.
>
> Is it a known bug ?
Jean-Claude,
It is a known "feature".
ECW does not support palettes so what you need to do is first convert your
8bit+palette image into a 24bit RGB image. This can be accomplished using
the pct2rgb.py script if you have a full (python enabled) build of GDAL
such as you get with FWTools.
pct2rgb.py test.png test24.tif
gdal_translate ... test24.tif test.ecw
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
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