[gdal-dev] Converting ecw to tif for Geoserver

[Etienne Tourigny]

On Sat, Feb 9, 2013 at 12:11 PM, Paul Meems <bontepaarden at gmail.com> wrote:
> Thanks Even,
>
> The low-res option really helped. Now I can test the commands in seconds
> instead of hours.
> I did these commands which seem to produce a tif file with overviews and
> correct transparency.
> I've opened it in MapWindow for now to check. MapWindow is using GDAL to
> read raster files.
>
> I will now convert the hi-res version and try that version in Geoserver.
> Here are the commands I used:
>
> # Create a low-res version:
> gdal_translate my.ecw test\lowres.tif -outsize 1% 1%
>
> # Fix the almost white pixels:
> nearblack -of GTiff -white -o lowres-white.tif lowres.tif
>
>
> # Warp and mark white pixels as transparent
> gdalwarp -multi -of GTiff -dstalpha -srcnodata "255 255 255" -co tiled=yes
> -co "BLOCKXSIZE=512" -co "BLOCKYSIZE=512" -s_srs EPSG:28992 -r lanczos
> -overwrite lowres-white.tif lowres-transparent.tif
>
> # Create internal tiles, don't use mask band because Geoserver doesn't like
> that:
> gdal_translate -of GTiff -a_srs EPSG:28992 -b 1 -b 2 -b 3 -co tiled=yes -co
> compress=jpeg -co photometric=YCBCR -co BLOCKXSIZE=512 -co BLOCKYSIZE=512
> --config GDAL_TIFF_INTERNAL_MASK YES lowres-transparent.tif
> lowres-compressed.tif
>
> # nodata is now black, but not all pixels are truly black:
> nearblack -of GTiff -o lowres-compressed-black.tif lowres-compressed.tif
>
> # Set the nodata value to black:
> gdal_translate -a_nodata 0 lowres-compressed-black.tif
> lowres-compressed-transparent.tif

you need to add option to compress in these last two commands, or the
final one only

>
> # Add overviews
> gdaladdo -r average --config COMPRESS_OVERVIEW JPEG --config
> PHOTOMETRIC_OVERVIEW YCBCR lowres-compressed-transparent.tif 2 4 8 16 32 64
> 128
>
>
> Thanks all.
>
>
> Paul
>
> 2013/2/9 Even Rouault <even.rouault at mines-paris.org>
>>
>> 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
>
>
>
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