Error in gdaladdo documentation and examples

[Jukka Rahkonen]

Gdaladdo document and examples suggest that setting options for compressing external overviews also makes gdaladdo to create external overviews. This is not true but user must use the -ro option as well. This is tested with gdaladdo from FWTools 2.4.2. Parts in the gdaladdo document which, to my understanding, should be corrected or written more clear are these three:

1) External overviews created in TIFF format may be compressed using the COMPRESS_OVERVIEW configuration option. All compression methods, supported by the GeoTIFF driver, available here. (eg --config COMPRESS_OVERVIEW DEFLATE). The photometric interpretation can be set with --config PHOTOMETRIC_OVERVIEW {RGB,YCBCR,...}, and the interleaving with --config INTERLEAVE_OVERVIEW {PIXEL|BAND}.

More clear: "External overviews created in TIFF format by using the -ro option..."

2) Create an external compressed GeoTIFF overview file from the ERDAS .IMG file: gdaladdo --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16

Should be "gdaladdo -ro --config "

3) Create an external JPEG-compressed GeoTIFF overview file from a 3-band RGB dataset:

gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR

--config INTERLEAVE_OVERVIEW PIXEL rgb_dataset.ext 2 4 8 16

Should contain the -ro option as well.

[Even Rouault]

I've tried to improve the doc in r18091.

Actually your above statements are not completely exact. -ro is just needed when the dataset is itself a GeoTIFF. For other formats, like .jpeg, it isn't required. Hopefully this will be clearer now.