gdaladdo Man page

gdaladdo General Commands Manual gdaladdo

NAME

gdaladdo – gdaladdo builds or rebuilds overview images

SYNOPSIS

gdaladdo [-r {nearest,average,gauss,cubic,average_mp,average_magphase,mode}] [-b band] [-ro] [-clean] [–help-general] filename levels

DESCRIPTION

The gdaladdo utility can be used to build or rebuild overview images
for most supported file formats with one of several downsampling
algorithms.

-r {nearest
(default),average,gauss,cubic,average_mp,average_magphase,mode}:
Select a resampling algorithm.

-b band:
(available from GDAL 1.10) Select an input band band for overview
generation. Band numbering starts from 1. Multiple -b switches may
be used to select a set of input bands to generate overviews.

-ro:
(available from GDAL 1.6.0) open the dataset in read-only mode, in
order to generate external overview (for GeoTIFF especially).

-clean:
(available from GDAL 1.7.0) remove all overviews.

filename:
The file to build overviews for (or whose overviews must be
removed).

levels:
A list of integral overview levels to build. Ignored with -clean
option.

Mode (available from GDAL 1.6.0) selects the value which appears most
often of all the sampled points. average_mp is unsuitable for use.
Average_magphase averages complex data in mag/phase space. Nearest and
average are applicable to normal image data. Nearest applies a nearest
neighbour (simple sampling) resampler, while average computes the
average of all non-NODATA contributing pixels. Cubic resampling
(available from GDAL 1.7.0) applies a 4×4 approximate cubic convolution
kernel. Gauss resampling (available from GDAL 1.6.0) applies a Gaussian
kernel before computing the overview, which can lead to better results
than simple averaging in e.g case of sharp edges with high contrast or
noisy patterns. The advised level values should be 2, 4, 8, … so that
a 3×3 resampling Gaussian kernel is selected.

gdaladdo will honour properly NODATA_VALUES tuples (special dataset
metadata) so that only a given RGB triplet (in case of a RGB image)
will be considered as the nodata value and not each value of the
triplet independently per band.

Selecting a level value like 2 causes an overview level that is 1/2 the
resolution (in each dimension) of the base layer to be computed. If the
file has existing overview levels at a level selected, those levels
will be recomputed and rewritten in place.

For internal GeoTIFF overviews (or external overviews in GeoTIFF
format), note that -clean does not shrink the file. A later run of
gdaladdo with overview levels will cause the file to be expanded,
rather than reusing the space of the previously deleted overviews. If
you just want to change the resampling method on a file that already
has overviews computed, you don’t need to clean the existing overviews.

Some format drivers do not support overviews at all. Many format
drivers store overviews in a secondary file with the extension .ovr
that is actually in TIFF format. By default, the GeoTIFF driver stores
overviews internally to the file operated on (if it is writeable),
unless the -ro flag is specified.

Most drivers also support an alternate overview format using Erdas
Imagine format. To trigger this use the USE_RRD=YES configuration
option. This will place the overviews in an associated .aux file
suitable for direct use with Imagine or ArcGIS as well as GDAL
applications. (eg –config USE_RRD YES)

External overviews in GeoTIFF format
External overviews created in TIFF format may be compressed using the
COMPRESS_OVERVIEW configuration option. All compression methods,
supported by the GeoTIFF driver, are 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}.

For JPEG compressed external overviews, the JPEG quality can be set
with ‘–config JPEG_QUALITY_OVERVIEW value’ (GDAL 1.7.0 or later).

For LZW or DEFLATE compressed external overviews, the predictor value
can be set with ‘–config PREDICTOR_OVERVIEW 1|2|3’ (GDAL 1.8.0 or
later).

To produce the smallest possible JPEG-In-TIFF overviews, you should use
:

–config COMPRESS_OVERVIEW JPEG –config PHOTOMETRIC_OVERVIEW YCBCR –config INTERLEAVE_OVERVIEW PIXEL

Starting with GDAL 1.7.0, external overviews can be created in the
BigTIFF format by using the BIGTIFF_OVERVIEW configuration option :
–config BIGTIFF_OVERVIEW {IF_NEEDED|IF_SAFER|YES|NO}. The default
value is IF_NEEDED. The behaviour of this option is exactly the same as
the BIGTIFF creation option documented in the GeoTIFF driver
documentation.

· YES forces BigTIFF.
· NO forces classic TIFF.
· IF_NEEDED will only create a BigTIFF if it is clearly needed
(uncompressed, and overviews larger than 4GB).
· IF_SAFER will create BigTIFF if the resulting file might exceed 4GB.
See the documentation of the GeoTIFF driver for further explanations on
all those options.
EXAMPLE
Create overviews, embedded in the supplied TIFF file:
gdaladdo -r average abc.tif 2 4 8 16
Create an external compressed GeoTIFF overview file from the ERDAS .IMG
file:
gdaladdo -ro –config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16
Create an external JPEG-compressed GeoTIFF overview file from a 3-band
RGB dataset (if the dataset is a writeable GeoTIFF, you also need to
add the -ro option to force the generation of external overview):
gdaladdo –config COMPRESS_OVERVIEW JPEG –config PHOTOMETRIC_OVERVIEW YCBCR
–config INTERLEAVE_OVERVIEW PIXEL rgb_dataset.ext 2 4 8 16
Create an Erdas Imagine format overviews for the indicated JPEG file:
gdaladdo –config USE_RRD YES airphoto.jpg 3 9 27 81
AUTHORS
Frank Warmerdam warmerdam@pobox.com, Silke Reimer silke@intevation.de

GDAL Tue Apr 5 2016 gdaladdo