Frank,<br><br>I reported the bug the best I could: 1384.<br><br>Matt and Frank, <br>I certainly appreciate all the help I have received from both.<br>I hope to be able to give something back to GDAL soon. <br><br>Tx<br><br>
<div><span class="gmail_quote">On 12/7/06, <b class="gmail_sendername">Frank Warmerdam</b> <<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Matt Wilkie wrote:<br>> Hi Dori, gdal doesn't like something about the way the source image[1]<br>> is formatted. I can't view it in OpenEV or in QGIS, it just comes up as<br>> a black image even before trying to translate or merge. Histograms in
<br>> both programs come up blank. You should probably file a bug[2]<br>><br>> In the meantime, I was able to open the image using ossim<br>> imagelinker[3], so maybe give that a try (though being pressed for time
<br>> you may not have the time to learn it).<br>><br>><br>> [1]<br>> <a href="http://www.mediamax.com/izzybitsie/Hosted/AS_GMSNO_00_20061122205548.tif.gz">http://www.mediamax.com/izzybitsie/Hosted/AS_GMSNO_00_20061122205548.tif.gz
</a><br>> [2] <a href="http://bugzilla.remotesensing.org/enter_bug.cgi?product=GDAL">http://bugzilla.remotesensing.org/enter_bug.cgi?product=GDAL</a><br>> [3] <a href="http://www.ossim.org/OSSIM/Welcome.html">http://www.ossim.org/OSSIM/Welcome.html
</a><br><br>folks,<br><br>I'm afraid I lost track of this thread. I have now fetched the file and<br>inspected it. TIFF colors maps are supposed to have colors in the<br>range 0-65535 for each component instead of the usual 0-255 in other
<br>formats. It seems that this file has been incorrectly generated to<br>have the colormap between 0 and 255. So when GDAL converts it to<br>0-255 values (roughly by dividing by 256) everything ends up black.<br><br>So, the input files are screwed up.
<br><br>Any programs that ignore colormaps will just treat the images as<br>greyscale.<br><br>I also think this may be a fairly common failure with tiff generators<br>and that some applications may have special logic to look for files
<br>with all colormap values in the 0-255 range and avoid the rescaling<br>that should happen.<br><br>Dori - if you want to file a bug in the GDAL bugzilla (Matt provided<br>the link above) for this problem, I'll try and implement a "hack" so
<br>that these PCTs work properly. It would be nice to get this in place<br>in time for beta2.<br><br>Best regards,<br>--<br>---------------------------------------+--------------------------------------<br>I set the clouds in motion - turn up | Frank Warmerdam,
<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a><br>light and sound - activate the windows | <a href="http://pobox.com/~warmerdam">http://pobox.com/~warmerdam</a><br>and watch the world go round - Rush | President OSGeo,
<a href="http://osgeo.org">http://osgeo.org</a><br><br></blockquote></div><br>