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NAME

       gdaladdo - Builds or rebuilds overview images.

SYNOPSIS

          gdaladdo [-r {nearest,average,rms,bilinear,gauss,cubic,cubicspline,lanczos,average_magphase,mode}]
                  [-b band]* [-minsize val]
                  [-ro] [-clean] [-oo NAME=VALUE]* [--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,rms,gauss,cubic,cubicspline,lanczos,average_magphase,mode}
              Select a resampling algorithm.

              nearest applies a nearest neighbour (simple sampling) resampler

              average computes the average of all non-NODATA contributing pixels.  Starting  with
              GDAL  3.1,  this  is  a weighted average taking into account properly the weight of
              source pixels not contributing fully to the target pixel.

              rms computes the root mean squared / quadratic mean of all non-NODATA  contributing
              pixels (GDAL >= 3.3)

              bilinear applies a bilinear convolution kernel.

              gauss  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.

              cubic applies a cubic convolution kernel.

              cubicspline applies a B-Spline convolution kernel.

              lanczos applies a Lanczos windowed sinc convolution kernel.

              average_magphase averages complex data in mag/phase space.

              mode selects the value which appears most often of all the sampled points.

       -b <band>
              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    open the dataset in read-only mode, in order to  generate  external  overview  (for
              GeoTIFF especially).

       -clean remove all overviews.

       -oo NAME=VALUE
              Dataset open option (format specific)

       -minsize <val>
              Maximum  width or height of the smallest overview level. Only taken into account if
              explicit levels are not specified. Defaults to 256.

              New in version 2.3.

       <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.

              New in version 2.3: levels are no longer required to  build  overviews.   In  which
              case, appropriate overview power-of-two factors will be selected until the smallest
              overview is smaller than the value of the -minsize switch.

       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
       writable), 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.  (e.g. --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. (e.g. --config COMPRESS_OVERVIEW DEFLATE).  The photometric interpretation
       can  be  set  with  the  PHOTOMETRIC_OVERVIEW =RGB/YCBCR/... configuration option, and the
       interleaving with the INTERLEAVE_OVERVIEW =PIXEL/BAND configuration option.

       Since GDAL 3.6, COMPRESS_OVERVIEW and decl_configoption:INTERLEAVE_OVERVIEW  are  honoured
       when creating internal overviews of TIFF files.

       For  JPEG  compressed  external  and  internal overviews, the JPEG quality can be set with
       --config JPEG_QUALITY_OVERVIEW value.

       For WEBP compressed external and internal overviews, the WEBP quality  level  can  be  set
       with --config WEBP_LEVEL_OVERVIEW value. If not set, will default to 75.

       For WEBP compressed external and internal overviews, the WEBP lossless/lossy switch can be
       set with --config WEBP_LOSSLESS_OVERVIEW value. If not set, will default  to  NO  (lossy).
       Added in GDAL 3.6.0

       For  LERC  compressed  external and internal overviews, the max error threshold can be set
       with --config MAX_Z_ERROR_OVERVIEW value. If not set, will default to 0 (lossless).  Added
       in GDAL 3.4.1

       For  DEFLATE  or  LERC_DEFLATE compressed external and internal overviews, the compression
       level can be set with --config ZLEVEL_OVERVIEW value. If not set, will default to 6. Added
       in GDAL 3.4.1

       For  ZSTD  or  LERC_ZSTD compressed external and internal overviews, the compression level
       can be set with --config ZSTD_LEVEL_OVERVIEW value. If not set, will default to  9.  Added
       in GDAL 3.4.1

       For  LZW,  ZSTD  or  DEFLATE compressed external overviews, the predictor value can be set
       with --config PREDICTOR_OVERVIEW 1|2|3.

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

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

       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_SAFER starting with GDAL 2.3.0 (previously was IF_NEEDED).  The
       behavior 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.

       Sparse GeoTIFF overview files (that is tiles which are omitted if all their pixels are  at
       the  nodata  value,  when  there's  one,  or at 0 otherwise) can be obtained with --config
       SPARSE_OK_OVERVIEW ON. Added in GDAL 3.4.1

       See the documentation of the GTiff -- GeoTIFF File Format driver for further  explanations
       on all those options.

SETTING BLOCKSIZE IN GEOTIFF OVERVIEWS

       --config GDAL_TIFF_OVR_BLOCKSIZE <size>

       Example: --config GDAL_TIFF_OVR_BLOCKSIZE 256

       Default  value is 128, or starting with GDAL 3.1, if creating overviews on a tiled GeoTIFF
       file, the tile size of the full resolution image.  Note: without this  setting,  the  file
       can   have   the   full  resolution  image  with  a  blocksize  different  from  overviews
       blocksize.(e.g. full resolution image at blocksize 256, overviews at blocksize 128)

NODATA / SOURCE VALIDITY MASK HANDLING DURING RESAMPLING

       Invalid values in source pixels, either identified through a nodata value metadata set  on
       the source band, a mask band, an alpha band will not be used during resampling.

       The details of how it is taken into account depends on the resampling kernel:

       • for  nearest resampling, for each target pixel, one of the potential contributing source
         pixels is selected (in an implementation specific way). Its value is used as it,  be  it
         valid or invalid.

       • for  bilinear,  cubic,  cubicspline  and  lanczos, for each target pixel, the weights of
         contributing source pixels is set to zero to ignore them when they are masked.  There is
         an  extra  specificity  for  cubic:  given  that  some  of the weights in the kernel are
         negative, such strategy could lead to  strong  overshoot/undershoot  when  there  is  an
         alternance  of  valid  and  invalid  pixels.  Consequently,  if any of the horizontal or
         vertical direction, if the maximum number of valid source pixels in  each  dimension  is
         less than the radius of the resampling kernel, the target pixel is considered as nodata.

       • for  the  other  resampling  methods, source pixels contributing to the target pixel are
         ignored if masked. Only the valid ones are taken into account. If there  are  none,  the
         target pixel is considered as nodata.

MULTITHREADING

       New in version 3.2.

       The  GDAL_NUM_THREADS  configuration  option  can be set to ALL_CPUS or a integer value to
       specify the number of threads to use for overview computation.

C API

       Functionality of this utility can be done from C with GDALBuildOverviews().

EXAMPLES

       Create overviews, embedded in the supplied TIFF file, with automatic computation of levels
       (GDAL 2.3 or later)

          gdaladdo -r average abc.tif

       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 writable 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

       Create  overviews  for  a  specific  subdataset,  like for example one of potentially many
       raster layers in a GeoPackage (the "filename" parameter must be  driver  prefix,  filename
       and subdataset name, like e.g. shown by gdalinfo):

          gdaladdo GPKG:file.gpkg:layer

AUTHOR

       Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>

COPYRIGHT

       1998-2023

                                           Jul 06, 2023                               GDALADDO(1)