Dear devs,I'm experiencing an strange issue concerning overviews when I try to add overviews via Python. Essentially I want to create overviews for Greyscale images encoded in RGB, but on one overview level I always get colored pixels in a specific rectangle area of the image.
I created the boiled down test script to demonstrate what I am doing (create RGB grey image of certain size, save it to disk and apply overviews) which is available in the attachment. The script is called like that: `python test_overviews.py out.tif`
In my case I could see the colorfull overviews in QGIS (or MapServer WMS) if I zoomed out a little. A screenshot of QGIS with the image can be found in the attachment.
Strangely, I only have this issue on CentOS 6.3 (gdal 1.9.1, libgeotiff 1.4.0, libtiff 3.9.4) but not on my host Ubuntu 12.10 system (gdal 1.9.2, libgeotiff2 1.3.0, libtiff 4.0.2).
I tried different interpolation methods for the `BuildOverviews` function, with no effect. If I remove the level `2` or `4` from my level list, the effect does *not* show. A different image size results in a different colour and position of the rectangle and sometimes the rectangle is not visible at all.
The issue is the same when I use `gdaladdo out_no_ovr.tif 2 4 8 16`. Any idea on this? Regards, Fabian
<<attachment: screenshot.png>>
import sys
from osgeo import gdal, gdalconst
mem_drv = gdal.GetDriverByName('MEM')
ds = mem_drv.Create('',
852, # size X
549, # size Y
3, # bands
gdalconst.GDT_Byte)
for i in range(1, 4):
band = ds.GetRasterBand(i)
band.Fill(128)
driver = gdal.GetDriverByName("GTIFF")
out_ds = driver.CreateCopy(sys.argv[1], ds)
out_ds.BuildOverviews("NEAREST", [
2,
4,
8,
16
])
ds = None
out_ds = None
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