Scroll to navigation

GDAL_CALC(1) GDAL GDAL_CALC(1)

NAME

gdal_calc - Command line raster calculator with numpy syntax.

SYNOPSIS

gdal_calc.py --calc=expression --outfile=out_filename [-A filename]
             [--A_band=n] [-B...-Z filename] [other_options]


DESCRIPTION

Command line raster calculator with numpy syntax. Use any basic arithmetic supported by numpy arrays such as +, -, *, and \ along with logical operators such as >. Note that all files must have the same dimensions (unless extent option is used), but no projection checking is performed (unless projectionCheck option is used).

--help
Show this help message and exit

-h
The same as --help.

--calc=expression
Calculation in numpy syntax using +, -, /, *, or any numpy array functions (i.e. log10()`). Multiple ``--calc options can be listed to produce a multiband file (GDAL >= 3.2).

-A <filename>
Input gdal raster file, you can use any letter (a-z, A-Z). (lower case supported since GDAL 3.3)

A letter may be repeated (GDAL >= 3.3). The effect will be to create a 3-dim numpy array. In such a case, the calculation formula must use this input as a 3-dim array and must return a 2D array (see examples below). In case the calculation does not return a 2D array an error would be generated.


--A_band=<n>
Number of raster band for file A (default 1).

--outfile=<filename>
Output file to generate or fill.

--NoDataValue=<value>
Output NoDataValue (default datatype specific value). To indicate not setting a NoDataValue use --NoDataValue=none (GDAL >= 3.3)

NOTE:

Using the Python API: None value will indicate default datatype specific value. 'none' value will indicate not setting a NoDataValue.



--hideNoData
..versionadded:: 3.3

Ignores the input bands NoDataValue. By default, the input bands NoDataValue are not participating in the calculation. By setting this setting - no special treatment will be performed on the input NoDataValue. and they will be participating in the calculation as any other value. The output will not have a set NoDataValue, unless you explicitly specified a specific value by setting --NoDataValue=<value>.


--type=<datatype>
Output datatype, must be one of [Int32, Int16, Float64, UInt16, Byte, UInt32, Float32].

NOTE:

Despite the datatype set using --type, when doing intermediate aritmethic operations using operands of the same type, the operation result will honor the original datatype. This may lead into unexpected results in the final result.



--format=<gdal_format>
GDAL format for output file.

color-table=<filename>
Allows specifying a filename of a color table (or a ColorTable object) (with Palette Index interpretation) to be used for the output raster. Supported formats: txt (i.e. like gdaldem, but color names are not supported), qlr, qml (i.e. exported from QGIS)

--extent=<option>
..versionadded:: 3.3

this option determines how to handle rasters with different extents. this option is mutually exclusive with the projwin option, which is used for providing a custom extent. for all the options below the pixel size (resolution) and SRS (Spatial Reference System) of all the input rasters must be the same. ignore (default) - only the dimensions of the rasters are compared. if the dimensions do not agree the operation will fail. fail - the dimensions and the extent (bounds) of the rasters must agree, otherwise the operation will fail. union - the extent (bounds) of the output will be the minimal rectangle that contains all the input extents. intersect - the extent (bounds) of the output will be the maximal rectangle that is contained in all the input extents.


--projwin <ulx> <uly> <lrx> <lry>
..versionadded:: 3.3

this option provides a custom extent for the output, it is mutually exclusive with the extent option.


--projectionCheck
..versionadded:: 3.3

By default, no projection checking will be performed. By setting this option, if the projection is not the same for all bands then the operation will fail.


--creation-option=<option>
Passes a creation option to the output format driver. Multiple options may be listed. See format specific documentation for legal creation options for each format.

--co=<option>
The same as creation-option.

--allBands=[a-z, A-Z]
Process all bands of given raster (a-z, A-Z). Requires a single calc for all bands.

--overwrite
Overwrite output file if it already exists.

--debug
Print debugging information.

--quiet
Suppress progress messages.

PYTHON OPTIONS

..versionadded:: 3.3

The following options are available by using function the python interface of gdal_calc. They are not available using the command prompt.

user_namespace
A dictionary of custom functions or other names to be available for use in the Calc expression.

return_ds
If enabled, the output dataset would be returned from the function and not closed.

color_table
Allows specifying a ColorTable object (with Palette Index interpretation) to be used for the output raster.

EXAMPLE

Add two files together:

gdal_calc.py -A input1.tif -B input2.tif --outfile=result.tif --calc="A+B"


Average of two layers:

gdal_calc.py -A input1.tif -B input2.tif --outfile=result.tif --calc="(A+B)/2"


NOTE:

In the previous example, beware that if A and B inputs are of the same datatype, for example integers, you may need to force the conversion of one of the operands before the division operation.

gdal_calc.py -A input.tif -B input2.tif --outfile=result.tif --calc="(A.astype(numpy.float64) + B) / 2"




Add three files together (two options with the same result):

gdal_calc.py -A input1.tif -B input2.tif -C input3.tif --outfile=result.tif --calc="A+B+C"


..versionadded:: 3.3

gdal_calc.py -A input1.tif -A input2.tif -A input3.tif --outfile=result.tif --calc="numpy.sum(A,axis=0)".


Average of three layers (two options with the same result):

gdal_calc.py -A input1.tif -B input2.tif -C input3.tif --outfile=result.tif --calc="(A+B+C)/3"


..versionadded:: 3.3

gdal_calc.py -A input1.tif -A input2.tif -A input3.tif --outfile=result.tif --calc="numpy.average(a,axis=0)".


Maximum of three layers (two options with the same result):

gdal_calc.py -A input1.tif -B input2.tif -C input3.tif --outfile=result.tif --calc="numpy.max((A,B,C),axis=0)"


..versionadded:: 3.3

gdal_calc.py -A input1.tif -A input2.tif -A input3.tif --outfile=result.tif --calc="numpy.max(A,axis=0)"


Set values of zero and below to null:

gdal_calc.py -A input.tif --outfile=result.tif --calc="A*(A>0)" --NoDataValue=0


Using logical operator to keep a range of values from input:

gdal_calc.py -A input.tif --outfile=result.tif --calc="A*logical_and(A>100,A<150)"


Work with multiple bands:

gdal_calc.py -A input.tif --A_band=1 -B input.tif --B_band=2 --outfile=result.tif --calc="(A+B)/2" --calc="B*logical_and(A>100,A<150)"


AUTHOR

Chris Yesson <chris dot yesson at ioz dot ac dot uk>, Etienne Tourigny <etourigny dot dev at gmail dot com>

COPYRIGHT

1998-2021
September 1, 2021