gdaladdo

gdaladdo(1)                 General Commands Manual                gdaladdo(1)



NAME
       gdaladdo - gdaladdo builds or rebuilds overview images

SYNOPSIS
       gdaladdo [-r {nearest,average,gauss,average_mp,average_magphase,mode}]
                [-ro] [--help-general] filename levels

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

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

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

       filename:
           The file to build overviews for.

       levels:
           A list of integral overview levels to build.

       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. 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 3x3 resampling
       Gaussian kernel is selected.

       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.

       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. The GeoTIFF driver stores overviews
       internally to the file operated on, unless the -ro flag is specified.

       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}.

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

       --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL


       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)

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 --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16

       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

       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                              4 Dec 2008                       gdaladdo(1)