1gdaladdo(1) General Commands Manual gdaladdo(1)
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6 gdaladdo - .TH "gdaladdo" 1 "Fri Apr 22 2011" "GDAL"
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9 gdaladdo - builds or rebuilds overview images
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12 gdaladdo [-r {nearest,average,gauss,cubic,average_mp,average_magphase,mode}]
13 [-ro] [-clean] [--help-general] filename levels
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16 The gdaladdo utility can be used to build or rebuild overview images
17 for most supported file formats with one over several downsampling
18 algorithms.
19 -r {nearest
21 (default),average,gauss,cubic,average_mp,average_magphase,mode}:
22 Select a resampling algorithm.
23 -ro:
25 (available from GDAL 1.6.0) open the dataset in read-only mode, in
26 order to generate external overview (for GeoTIFF especially).
27 -clean:
29 (available from GDAL 1.7.0) remove all overviews.
30 filename:
32 The file to build overviews for (or whose overviews must be
33 removed).
34 levels:
36 A list of integral overview levels to build. Ignored with -clean
37 option.
38 Mode (available from GDAL 1.6.0) selects the value which appears most
40 often of all the sampled points. average_mp is unsuitable for use.
41 Average_magphase averages complex data in mag/phase space. Nearest and
42 average are applicable to normal image data. Nearest applies a nearest
43 neighbour (simple sampling) resampler, while average computes the
44 average of all non-NODATA contributing pixels. Cubic resampling
45 (available from GDAL 1.7.0) applies a 4x4 approximate cubic convolution
46 kernel. Gauss resampling (available from GDAL 1.6.0) applies a Gaussian
47 kernel before computing the overview, which can lead to better results
48 than simple averaging in e.g case of sharp edges with high contrast or
49 noisy patterns. The advised level values should be 2, 4, 8, ... so that
50 a 3x3 resampling Gaussian kernel is selected.
51 gdaladdo will honour properly NODATA_VALUES tuples (special dataset
53 metadata) so that only a given RGB triplet (in case of a RGB image)
54 will be considered as the nodata value and not each value of the
55 triplet independantly per band.
56 Selecting a level value like 2 causes an overview level that is 1/2 the
58 resolution (in each dimension) of the base layer to be computed. If the
59 file has existing overview levels at a level selected, those levels
60 will be recomputed and rewritten in place.
61 Some format drivers do not support overviews at all. Many format
63 drivers store overviews in a secondary file with the extension .ovr
64 that is actually in TIFF format. By default, the GeoTIFF driver stores
65 overviews internally to the file operated on (if it is writable),
66 unless the -ro flag is specified.
67 External overviews created in TIFF format may be compressed using the
69 COMPRESS_OVERVIEW configuration option. All compression methods,
70 supported by the GeoTIFF driver, available here. (eg --config
71 COMPRESS_OVERVIEW DEFLATE). The photometric interpretation can be set
72 with --config PHOTOMETRIC_OVERVIEW {RGB,YCBCR,...}, and the
73 interleaving with --config INTERLEAVE_OVERVIEW {PIXEL|BAND}.
74 To produce the smallest possible JPEG-In-TIFF overviews, you should use
76 :
77 --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL
79 Starting with GDAL 1.7.0, external overviews can be created in the
82 BigTIFF format by using the BIGTIFF_OVERVIEW configuration option :
83 --config BIGTIFF_OVERVIEW {IF_NEEDED|IF_SAFER|YES|NO}. The default
84 value is IF_NEEDED. The behaviour of this option is exactly the same as
85 the BIGTIFF creation option documented in the GeoTIFF driver
86 documentation.
87 · YES forces BigTIFF.
89 · NO forces classic TIFF.
90 · IF_NEEDED will only create a BigTIFF if it is clearly needed
91 (uncompressed, and overviews larger than 4GB).
92 · IF_SAFER will create BigTIFF if the resulting file *might* exceed
93 4GB.
94 Most drivers also support an alternate overview format using Erdas
95 Imagine format. To trigger this use the USE_RRD=YES configuration
96 option. This will place the overviews in an associated .aux file
97 suitable for direct use with Imagine or ArcGIS as well as GDAL
98 applications. (eg --config USE_RRD YES)
100 Create overviews, embedded in the supplied TIFF file:
101 gdaladdo -r average abc.tif 2 4 8 16
102 Create an external compressed GeoTIFF overview file from the ERDAS .IMG
103 file:
104 gdaladdo -ro --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16
105 Create an external JPEG-compressed GeoTIFF overview file from a 3-band
106 RGB dataset (if the dataset is a writable GeoTIFF, you also need to add
107 the -ro option to force the generation of external overview):
108 gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR
109 --config INTERLEAVE_OVERVIEW PIXEL rgb_dataset.ext 2 4 8 16
110 Create an Erdas Imagine format overviews for the indicated JPEG file:
111 gdaladdo --config USE_RRD YES airphoto.jpg 3 9 27 81
113 Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer
114 <silke@intevation.de>
115GDAL Fri Apr 22 2011 gdaladdo(1)