Open smit1678 opened 7 years ago
The source file is 18GB on a slow FTP connection, so I can only go off of what it was transcoded into. (Though if @ragnvald has access to the original, I'd like to see what the output of gdalinfo
against it is.)
The transcoded version has 3 bands and no NODATA values (per gdalinfo /vsicurl/http://oin-hotosm.s3.amazonaws.com/598d7c5aa260c700113db24d/0/e77bbf55-a505-4a25-9de1-7ed667b88bfa.tif
). The white areas are white (255, 255, 255) and the black areas black (0, 0, 0), so I suspect that the same may be true for the source.
The black and white areas need to be masked out either by creating a mask or alpha band. (Since the band types are all Byte
, NODATA values are problematic (they need to be in the range of 0-255, which are also valid colors).
Unfortunately, I don't have any quick/simple solutions for adding mask bands.
This is the GDAL info from a similar file:
Driver: GTiff/GeoTIFF Files: E:/ghana_coast/norkart_fiksa/output_qgis_merger/phase-6_modified_2.tif Size is 80016, 37806 Coordinate System is: PROJCS["unnamed", GEOGCS["Clarke 1880 mod.", DATUM["unknown", SPHEROID["clrk80",6378249.145,293.4663], TOWGS84[-130,29,364,0,0,0,0]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",4.666666666666667], PARAMETER["central_meridian",-1], PARAMETER["scale_factor",0.99975], PARAMETER["false_easting",274319.51], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]]] Origin = (207999.849344947375357,58396.820743878321082) Pixel Size = (0.499910369967251,-0.499910369967251) Metadata: AREA_OR_POINT=Area Image Structure Metadata: INTERLEAVE=PIXEL Corner Coordinates: Upper Left ( 207999.849, 58396.821) ( 1d35'53.98"W, 5d11'40.73"N) Lower Left ( 207999.849, 39497.209) ( 1d35'53.41"W, 5d 1'25.28"N) Upper Right ( 248000.678, 58396.821) ( 1d14'14.82"W, 5d11'41.59"N) Lower Right ( 248000.678, 39497.209) ( 1d14'14.59"W, 5d 1'26.11"N) Center ( 228000.263, 48947.015) ( 1d25' 4.21"W, 5d 6'33.52"N) Band 1 Block=80016x1 Type=Byte, ColorInterp=Red Band 2 Block=80016x1 Type=Byte, ColorInterp=Green Band 3 Block=80016x1 Type=Byte, ColorInterp=Blue
I guess if I could automate the selection (wand-type select) for both bigger black and white areas I could create a mask which is then used as an alpha-channel. I am however some of a novice in raster data handling, so if you know someone which could describe a procedure in QGIS it would be grand.
Via report form on website from @ragnvald:
Image on OAM: https://map.openaerialmap.org/#/-0.11981964111328125,5.5619986997627,11/03333311110/598d829d46e19904aab0a92a?_k=qrpy46
@mojodna suggestions?