[gdal-dev] Antialiasing problem with gdaladdo at edges/nodata sections

[Neumann, Andreas]

Hi, 

I have Orthoimages where the boundaries aren't rectangular, but they
have corners and sometimes even diagonal edges. 

I noticed, that after creating pyramids/overview with gdaladdo, that I
get antialiasing/rendering artefacts that aren't present in the original
image at full resolution. See attached image that shows the problem. I
used a pink background to emphasize the problem. 

My nodata values are set to white (rgb 255,255,255) in the original
image. 

Here is the gdaladdo command that I used: 

gdaladdo -r cubic --config BIGTIFF_OVERVIEW YES --config
COMPRESS_OVERVIEW JPEG --config JPEG_QUALITY 85 --config
PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL
dop2002_lv95.tif 2 4 8 16 32 64 128 256 512 1024 

This is the output of gdalinfo on the original image: 

----------------------- 

Driver: GTiff/GeoTIFF
Files: dop2002_lv95 - Kopie.tif
Size is 240000, 190000
Coordinate System is:
PROJCS["CH1903+ / LV95",
GEOGCS["CH1903+",
DATUM["CH1903+",
SPHEROID["Bessel 1841",6377397.155,299.1528128,
AUTHORITY["EPSG","7004"]],
TOWGS84[674.374,15.056,405.346,0,0,0,0],
AUTHORITY["EPSG","6150"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4150"]],
PROJECTION["Hotine_Oblique_Mercator_Azimuth_Center"],
PARAMETER["latitude_of_center",46.95240555555556],
PARAMETER["longitude_of_center",7.439583333333333],
PARAMETER["azimuth",90],
PARAMETER["rectified_grid_angle",90],
PARAMETER["scale_factor",1],
PARAMETER["false_easting",2600000],
PARAMETER["false_northing",1200000],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["Easting",EAST],
AXIS["Northing",NORTH],
AUTHORITY["EPSG","2056"]]
Origin = (672000.000000000000000,234000.000000000000000)
Pixel Size = (0.100000000000000,-0.100000000000000)
Metadata:
AREA_OR_POINT=Area
TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
TIFFTAG_XRESOLUTION=1
TIFFTAG_YRESOLUTION=1
Image Structure Metadata:
COMPRESSION=YCbCr JPEG
INTERLEAVE=PIXEL
SOURCE_COLOR_SPACE=YCbCr
Corner Coordinates:
Upper Left ( 672000.000, 234000.000) ( 13d51' 5.78"W, 35d55'48.10"N)
Lower Left ( 672000.000, 215000.000) ( 13d47'45.10"W, 35d46' 1.03"N)
Upper Right ( 696000.000, 234000.000) ( 13d35'53.15"W, 35d59'13.56"N)
Lower Right ( 696000.000, 215000.000) ( 13d32'34.61"W, 35d49'25.99"N)
Center ( 684000.000, 224500.000) ( 13d41'49.73"W, 35d52'37.44"N)
Band 1 Block=256x256 Type=Byte, ColorInterp=Red
NoData Value=255
Band 2 Block=256x256 Type=Byte, ColorInterp=Green
NoData Value=255
Band 3 Block=256x256 Type=Byte, ColorInterp=Blue
NoData Value=255 

-------------------------------------------------------------------------------


Is there a way to get rid of these artefacts at the nodata borders? 

Thank you and greetings, 

Andreas 

  
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