Reading a specific overview layer from GeoTIFF file using GDAL / Python

Question

I know how to create the overviews to a specific geoTIFF file using GDAL ( i have tested it in QGIS), but I cannot find any good information on how to read these overviews individually in Python.

gdal.SetConfigOption('HFA_USE_RRD', 'YES')
outData = gdal.Open("test2.tiff",gdal.GA_Update)
outData.BuildOverviews(overviewlist=[2,4,8])

i would expect the answer to be something like:

array = outData.GetOverviews(overviewlist = 2)

Answer 1

The reason to my problem was that I was not calling the function from the right class. GetOverview is called from the class Band.

Answer 2

Here is the python gdal code to extract overview from Sentinel 2 JP2 format with overview level 2 (0-index).

import gdal
jp2 = "T32UMD_20190727T104029_TCI_10m.jp2"

dataset = gdal.Open(jp2)

band1 = dataset.GetRasterBand(1);
overview1 = band1.GetOverview(2);

band2 = dataset.GetRasterBand(2);
overview2 = band2.GetOverview(2);    

band3 = dataset.GetRasterBand(3);
overview3 = band3.GetOverview(2);

arr1 = overview1.ReadAsArray()
arr2 = overview2.ReadAsArray()
arr3 = overview3.ReadAsArray()

[cols, rows] = arr1.shape

driver = gdal.GetDriverByName("GTiff")
outdata = driver.Create("test_overview.tiff", rows, cols, 3, gdal.GDT_Byte)

outdata.GetRasterBand(1).WriteArray(arr1)
outdata.GetRasterBand(2).WriteArray(arr2)
outdata.GetRasterBand(3).WriteArray(arr3)

outdata.FlushCache() ##saves to disk!!
outdata = None
band=None
ds=None