Le mercredi 28 mai 2014 16:35:39, Jonathan Moules a écrit : > Hi List, > I have four band (RGB plus Infrared) imagery from some aerial photography > we've had flown. I've already used GDAL to create suitable optimised RGB > GeoTIFFs using this data and now want to do it with the Infrared band too. > > The RGBI data is about 1TB uncompressed, currently stored as 2732 GeoTIFF > tiles compressed with LZW: > > Files: SK1400.tif > > > SK1400.tfw > > > > Size is 8000, 8000 > > Coordinate System is: > > PROJCS["OSGB 1936 / British National Grid", > > > > GEOGCS["OSGB 1936", > > > > DATUM["OSGB_1936", > > > > SPHEROID["Airy 1830",6377563.396,299.3249753150316, > > > > AUTHORITY["EPSG","7001"]], > > > > AUTHORITY["EPSG","6277"]], > > > > PRIMEM["Greenwich",0], > > UNIT["degree",0.0174532925199433], > > AUTHORITY["EPSG","4277"]], > > > > PROJECTION["Transverse_Mercator"], > > PARAMETER["latitude_of_origin",49], > > PARAMETER["central_meridian",-2], > > PARAMETER["scale_factor",0.9996012717], > > PARAMETER["false_easting",400000], > > PARAMETER["false_northing",-100000], > > UNIT["metre",1, > > > > AUTHORITY["EPSG","9001"]], > > > > AUTHORITY["EPSG","27700"]] > > > > Origin = (414000.000000000000000,301000.000000000000000) > > Pixel Size = (0.125000000000000,-0.125000000000000) > > > > Metadata: > > AREA_OR_POINT=Area > > > > Image Structure Metadata: > > COMPRESSION=LZW > > INTERLEAVE=PIXEL > > > > Corner Coordinates: > > Upper Left ( 414000.000, 301000.000) ( 1d47'35.68"W, 52d36'22.49"N) > > Lower Left ( 414000.000, 300000.000) ( 1d47'35.83"W, 52d35'50.12"N) > > Upper Right ( 415000.000, 301000.000) ( 1d46'42.51"W, 52d36'22.40"N) > > Lower Right ( 415000.000, 300000.000) ( 1d46'42.68"W, 52d35'50.03"N) > > Center ( 414500.000, 300500.000) ( 1d47' 9.18"W, 52d36' 6.26"N) > > Band 1 Block=8000x32 Type=Byte, ColorInterp=Red > > Band 2 Block=8000x32 Type=Byte, ColorInterp=Green > > Band 3 Block=8000x32 Type=Byte, ColorInterp=Blue > > Band 4 Block=8000x32 Type=Byte, ColorInterp=Undefined > > My goal is to create a mosaiced GeoTIFF image with all four bands in it. It > should be as small as possible without serious quality degredation. > > > I've got some some questions as a result of my experiments so far: > > > - "-co PHOTOMETRIC=YCBCR" - in gdal_translate this will fail saying it > only works with 3 bands. Yet with gdaladdo, compressing overviews with > "--config PHOTOMETRIC_OVERVIEW YCBCR" works fine (or at least gives no > errors). Any reason for this?
--config PHOTOMETRIC_OVERVIEW YCBCR is ignored if you build internal GTiff overview. And I've just tested with external overview and it fails as expected : $ gdaladdo 4band.tif 2 --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR -ro ERROR 6: PHOTOMETRIC_OVERVIEW=YCBCR requires a source raster with only 3 bands (RGB) Overview building failed. > - Is there any special compression to use for four band imagery as I > can't use YCBCR? Just base JPEG compression > - What's the best way to process the data? I'm using: > > gdal_translate aerial.vrt aerial.tif -of GTiff -co BIGTIFF=YES -co > > > TILED=YES -co blockxsize=512 -co blockysize=512 -co COMPRESS=JPEG -co > > JPEG_QUALITY=50 -a_srs EPSG:27700 > > gdaladdo aerial.tif -r average --config COMPRESS_OVERVIEW JPEG --config > > JPEG_QUALITY_OVERVIEW 50 --config INTERLEAVE_OVERVIEW PIXEL --config > > PHOTOMETRIC_OVERVIEW YCBCR 2 4 8 16 32 As said above, the --config options will be ignored for internal overviews (except JPEG_QUALITY_OVERVIEW actually). They will reuse the same setting as the full resolution bands > > - How do I get GDAL to *not *set Band 4 to "Alpha" (which is what the > above does). Add -co ALPHA=UNSPECIFIED > > Using GDAL 1.10.1 > > Thanks, > Jonathan -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev