Le samedi 09 février 2013 13:48:13, Paul Meems a écrit : > The last days I've been trying to convert my ecw file to a GeoTiff so I can > use it in Geoserver. > The ecw is a mozaik of aerial photos. > When I do these two commands it is working in Geoserver: > > - gdal_translate -of GTiff -co tiled=yes -co compress=jpeg -co > photometric=YCBCR -a_srs EPSG:28992 -co "BLOCKXSIZE=512" -co > "BLOCKYSIZE=512" my.ecw my.tif > - gdaladdo -r average --config COMPRESS_OVERVIEW JPEG --config > PHOTOMETRIC_OVERVIEW YCBCR my.tif 2 4 8 16 32 64 128 > > But I want to add a second reference layer beneath this one which is > larger. The translated ecw has white edges, so that is not looking nice. > I've asked about this before and suggested was to use a cutline. So I > create a polygon that is inside the ecw file and ran this command: > > - gdalwarp -multi -cutline "clip.shp" -of GTiff -co tiled=yes -co > compress=jpeg -co photometric=YCBCR -co "BLOCKXSIZE=512" -co > "BLOCKYSIZE=512" -s_srs EPSG:28992 -r lanczos -overwrite my.ecw > clipped.tif > > When I open clipped.tif in MapWindow I can see the white edges are gone. > But when I call *gdaladdo* white artifacts are back again.
I'm not clear why gdaladdo would add while artifacts if clipped.tif has no more white borders (i.e. if your clipping shape is a rectangle completely inside the validity area of the ECW). Unless clipped.tif has an alpha channel, but the gdalwarp command line you showed has no -dstalpha. But that wouldn't work actually since you use JPEG YCbCr compression, which doesn't support alpha channels. A solution - provided that MapWindows supports GDAL mask bands as transparency channels - would be : # Warp and mark white pixels as transparent gdalwarp 1.tif 2.tif -dstalpha -srcnodata "255 255 255" [other_options] # Transform 2.tif as a JPEG-YCBCR-in-TIFF with an internal mask band gdal_translate 2.tif 3.tif -b 1 -b 2 -b 3 -mask 4 -co compress=jpeg -co photometric=YCBCR -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 --config GDAL_TIFF_INTERNAL_MASK YES # Add overviews gdaladdo 3.tif -r average --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR 2 4 > I'm now in the process of calling *nearblack* on both my.tiff and > clipped.tif but I'm not sure I'm doing it right. I think I'm using the > correct commands but perhaps in the wrong order. > The ecw file isn't very large (2.6GB) but all steps take a long time, > especially *nearblack *which is running for 4 hours now and is just at 10%. > For the experiments, I'd encourage working with a low res extract of the ECW : gdal_translate src.ecw lowres.tif -outsize 1% 1% > Does anybody have some suggestions how to process the steps to convert an > ecw file which has white outside areas to a transparent tif file with > overviews? > > I'm running the latest GDAL v1.10 version from Tamas on Windows Vista on a > 8GB 4core machine. Speed is not a big issue when I know the result will be > OK. Another point: It is well known that warping with compression doesn't produce files with optimal size. See http://trac.osgeo.org/gdal/wiki/UserDocs/GdalWarp#GeoTIFFoutput- coCOMPRESSisbroken > > Thanks, > > Paul _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
