ahmet,<br><br>One likely reason for the dark image is that your viewer is assuming a range of 0-65535 for the alpha values.<br>Check the histogram of the output image. In the
histogram for the second band, there should be a bunch of 0 valued
pixels and 255 valued pixels.<br>Please provide a small sample image if the problem persists.<br>
<br><br><div class="gmail_quote">2011/2/6 ahmet temiz <span dir="ltr"><<a href="mailto:ahmettemiz88@gmail.com">ahmettemiz88@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
hello<br>
<br>
I want to make nodata areas transparent.<br>
<br>
here is what I did:<br>
<br>
1.<br>
$gdalinfo -mm -noct duy_cat1.tif | grep -i 'nodata'<br>
NoData Value=65535<br>
<br>
2.<br>
gdalwarp -srcnodata 65535 -dstalpha duy_cat1.tif duy_cat14.tif<br>
<br>
But, duy_cat14.tif looks full black<br>
<br>
here is info of outputfile(duy_cat14.tif):<br>
~~~~~~~~~~<br>
Driver: GTiff/GeoTIFF<br>
Files: duy_cat14.tif<br>
Size is 4677, 5527<br>
Coordinate System is:<br>
PROJCS["UTM Zone 36, Northern Hemisphere",<br>
GEOGCS[,<br>
DATUM["unknown",<br>
SPHEROID["unnamed",6378388,297.000000000005]],<br>
PRIMEM["Greenwich",0],<br>
UNIT["degree",0.0174532925199433]],<br>
PROJECTION["Transverse_Mercator"],<br>
PARAMETER["latitude_of_origin",0],<br>
PARAMETER["central_meridian",33],<br>
PARAMETER["scale_factor",0.9996],<br>
PARAMETER["false_easting",500000],<br>
PARAMETER["false_northing",0],<br>
UNIT["metre",1,<br>
AUTHORITY["EPSG","9001"]]]<br>
Origin = (437192.936421879974660,4649982.939232329837978)<br>
Pixel Size = (20.004039786776190,-20.004039786776190)<br>
Metadata:<br>
AREA_OR_POINT=Area<br>
Image Structure Metadata:<br>
INTERLEAVE=PIXEL<br>
Corner Coordinates:<br>
Upper Left ( 437192.936, 4649982.939) ( 32d14'30.03"E, 41d59'55.01"N)<br>
Lower Left ( 437192.936, 4539420.611) ( 32d15'11.54"E, 41d 0'10.24"N)<br>
Upper Right ( 530751.831, 4649982.939) ( 33d22'16.70"E, 42d 0'1.87"N)<br>
Lower Right ( 530751.831, 4539420.611) ( 33d21'56.38"E, 41d 0'16.87"N)<br>
Center ( 483972.383, 4594701.775) ( 32d48'28.68"E, 41d30'10.99"N)<br>
Band 1 Block=4677x1 Type=UInt16, ColorInterp=Palette<br>
Computed Min/Max=0.000,65449.000<br>
Color Table (RGB with 65536 entries)<br>
Band 2 Block=4677x1 Type=UInt16, ColorInterp=Alpha<br>
Computed Min/Max=0.000,255.000<br>
~~~~~~~~~~~<br>
<br>
could you tell me where the problem is ?<br>
<br>
regards<br>
--<br>
Ahmet Temiz<br>
Jeoloji Müh.<br>
Planlama ve Zarar Azaltma Dairesi Başkanlığı<br>
Bilgi ve CBS grubu<br>
Eskişehir Yolu 10. km.<br>
Lodumlu / Ankara<br>
Tel : 0 312 2872680 / 1535<br>
_______________________________________________<br>
gdal-dev mailing list<br>
<a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br>
<a href="http://lists.osgeo.org/mailman/listinfo/gdal-dev" target="_blank">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a><br>
</blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9494447584<br>17.2416N 80.1426E<br>