Command-line interface

OTB ships with more than 100 ready to use applications for remote sensing tasks. They usually expose existing processing functions from the underlying C++ library, or integrate them into high level pipelines. OTB applications allow the user to:

  • Combine two or more functions from the Orfeo ToolBox,

  • Provide a high level interface to handle: input and output data, definition of parameters and communication with the user.

OTB applications can be launched in different ways, and accessed from different entry points. While the framework can be extended, the Orfeo ToolBox ships with the following:

  • A command-line launcher, to call applications from the terminal,

  • A SWIG interface, which means that any application can be loaded, set-up and executed into a high-level language such as Python for instance.

  • A QGIS interface based on the providers is built on top of the SWIG/Python interface and is available with seamless integration within QGIS.

The complete list of applications is described in the Chapter Applications by module.

All standard applications share the same implementation and automatically expose generated interfaces. However they are accessed in a slightly different way: the command-line interface is prefixed by otbcli_. For instance, calling otbcli_DynamicConvert will launch the command-line interface of the DynamicConvert application.

Command-line launcher

The command-line application launcher loads an application plugin, allows for its parameters to be set, and can then be executed from the command line. Launching the otbApplicationLauncherCommandLine without any arguments provided, results in the following help to be displayed:

$ otbApplicationLauncherCommandLine
Usage: ./otbApplicationLauncherCommandLine module_name [MODULEPATH] [arguments]

The module_name parameter corresponds to the application name. The [MODULEPATH] argument is optional and allows the path to the shared library (or plugin) corresponding to the module_name to be passed to the launcher.

It is also possible to set this path with the environment variable OTB_APPLICATION_PATH, making the [MODULEPATH] optional. This variable is checked by default when no [MODULEPATH] argument is given. When using multiple paths in OTB_APPLICATION_PATH, one must ensure that the standard path separator of the target system is used, which is : on Unix and ; on Windows.

An error in the application name (i.e. in parameter module_name) will make the otbApplicationLauncherCommandLine list the name of all applications found in the available path (either [MODULEPATH] and/or OTB_APPLICATION_PATH).

To ease the use of the applications, and to avoid extensive environment customizations; ready-to-use scripts are provided by the OTB installation to launch each application. They take care of adding the standard application installation path to the OTB_APPLICATION_PATH environment variable.

These scripts are named otbcli_<ApplicationName> and do not need any path settings. For example, you can start the Orthorectification application with the script called otbcli_Orthorectification.

Launching an application without parameters, or with incomplete parameters, will cause the launcher to display a summary of the parameters. This summary will display the minimum set of parameters that are required to execute the application. Here is an example based on the OrthoRectification application:

$ otbcli_OrthoRectification
ERROR: Waiting for at least one parameter.

This is the Ortho-rectification (OrthoRectification) application, version 6.7.0

This application allows ortho-rectifying optical and radar images from supported sensors.
Complete documentation: or -help

        -io                      <group>          Input and output data
MISSING                   <string>         Input Image  (mandatory)
MISSING -io.out                  <string> [pixel] Output Image  [pixel=uint8/uint16/int16/uint32/int32/float/double/cint16/cint32/cfloat/cdouble] (default value is float) (mandatory)
        -map                     <string>         Map Projection [utm/lambert2/lambert93/wgs/epsg] (mandatory, default value is utm)            <int32>          Zone number  (mandatory, default value is 31)
        -map.utm.northhem        <boolean>        Northern Hemisphere  (mandatory, default value is false)
        -map.epsg.code           <int32>          EPSG Code  (mandatory, default value is 4326)
        -outputs                 <group>          Output Image Grid
        -outputs.mode            <string>         Parameters estimation modes [auto/autosize/autospacing/outputroi/orthofit] (mandatory, default value is auto)
MISSING -outputs.ulx             <float>          Upper Left X  (mandatory)
MISSING -outputs.uly             <float>          Upper Left Y  (mandatory)
MISSING -outputs.sizex           <int32>          Size X  (mandatory)
MISSING -outputs.sizey           <int32>          Size Y  (mandatory)
MISSING -outputs.spacingx        <float>          Pixel Size X  (mandatory)
MISSING -outputs.spacingy        <float>          Pixel Size Y  (mandatory)
        -outputs.lrx             <float>          Lower right X  (optional, off by default)
        -outputs.lry             <float>          Lower right Y  (optional, off by default)
        -outputs.ortho           <string>         Model ortho-image  (optional, off by default)
        -outputs.isotropic       <boolean>        Force isotropic spacing by default  (mandatory, default value is true)
        -outputs.default         <float>          Default pixel value  (optional, off by default, default value is 0)
        -elev                    <group>          Elevation management
        -elev.dem                <string>         DEM directory  (optional, off by default)
        -elev.geoid              <string>         Geoid File  (optional, off by default)
        -elev.default            <float>          Default elevation  (mandatory, default value is 0)
        -interpolator            <string>         Interpolation [bco/nn/linear] (mandatory, default value is bco)
        -interpolator.bco.radius <int32>          Radius for bicubic interpolation  (mandatory, default value is 2)
        -opt                     <group>          Speed optimization parameters
        -opt.rpc                 <int32>          RPC modeling (points per axis)  (optional, off by default, default value is 10)
        -opt.ram                 <int32>          Available RAM (MB)  (optional, off by default, default value is 128)
        -opt.gridspacing         <float>          Resampling grid spacing  (optional, off by default, default value is 4)
        -progress                <boolean>        Report progress
        -help                    <string list>    Display long help (empty list), or help for given parameters keys

Use -help param1 [... paramN] to see detailed documentation of those parameters.

otbcli_OrthoRectification QB_TOULOUSE_MUL_Extract_500_500.tif -io.out QB_Toulouse_ortho.tif

For a detailed description of the application behaviour and parameters, please check the application reference documentation presented in chapter Applications by module  or follow the DOCUMENTATION hyperlink provided in the output of otbApplicationLauncherCommandLine. Parameters are passed to the application using the parameter key (which might include one or several . character), prefixed by a -. Command-line examples are provided in the chapter Applications by module.

Load and save parameters to XML

OTB application parameters can be saved and loaded to an XML file using the special -inxml and -outxml parameters. Those parameters are available in all applications. For example:

otbcli_BandMath -il input_image_1 input_image_2
                -exp "abs(im1b1 - im2b1)"
                -out output_image
                -outxml saved_applications_parameters.xml

Then, you can run the applications with the same parameters using the output XML file previously saved. For this, you have to use the inxml parameter:

otbcli_BandMath -inxml saved_applications_parameters.xml

Note that you can also add additional parameters to the command line at the same time

otbcli_BandMath -inxml saved_applications_parameters.xml
                -exp "(im1b1 - im2b1)"

In this case it will use as mathematical expression “(im1b1 - im2b1)” instead of “abs(im1b1 - im2b1)”.

Parallel execution with MPI

Provided that Orfeo ToolBox has been built with MPI and SPTW modules activated, it is possible to use MPI for massive parallel computation and writing of an output image. A simple call to mpirun before the command-line activates this behaviour, with the following logic. MPI writing is only triggered if:

  • OTB is built with MPI and SPTW,

  • The number of MPI processes is greater than 1,

  • The output filename is .tif or .vrt

In this case, the output image will be divided into several tiles according to the number of MPI processes specified to the mpirun command, and all tiles will be computed in parallel.

If the output filename extension is .tif, tiles will be written in parallel to a single Tiff file using SPTW (Simple Parallel Tiff Writer).

If the output filename extension is .vrt, each tile will be written to a separate Tiff file, and a global VRT file will be written.

Here is an example of MPI call on a cluster:

$ mpirun -np $nb_procs --hostfile $PBS_NODEFILE  \
  otbcli_BundleToPerfectSensor \
  -inp $ROOT/IMG_PHR1A_P_001/IMG_PHR1A_P_201605260427149_ORT_1792732101-001_R1C1.JP2 \
  -inxs $ROOT/IMG_PHR1A_MS_002/IMG_PHR1A_MS_201605260427149_ORT_1792732101-002_R1C1.JP2 \
  -out $ROOT/pxs.tif uint16 -ram 1024

  ------------ JOB INFO 1043196.tu-adm01 -------------

  JOBID           : 1043196.tu-adm01
  USER            : michelj
  GROUP           : ctsiap
  JOB NAME        : OTB_mpi
  SESSION         : 631249
  RES REQSTED     : mem=1575000mb,ncpus=560,place=free,walltime=04:00:00
  RES USED        : cpupercent=1553,cput=00:56:12,mem=4784872kb,ncpus=560,vmem=18558416kb,
  BILLING         : 42:46:40 (ncpus x walltime)
  QUEUE           : t72h
  ACCOUNT         : null

------------ END JOB INFO 1043196.tu-adm01 ---------

One can see that the registration and pan-sharpening of the panchromatic and multi-spectral bands of a Pleiades image has been split between 560 CPUs and only took 56 seconds to complete.

Note that this MPI parallel invocation of applications is only available for command-line calls to OTB applications, and only for images output parameters.