Standalone Tool Adapter

Overview

The Stand-Alone Tools Adapter is the glue between the Toolbox and an external tool.
It allows defining adapters - as GPF operators - for external processes/tools, that can be used either in a GPF graph or from the Toolbox GUI.
The three major responsibilities for the Stand-Alone Tools Adapter both in GUI and GPF operator mode are:

Provide the user's inputs from the Toolbox context to the external tool

If the tool is invoked from the Toolbox GUI, the Stand-Alone Tools Adapter takes care of the current GUI context and state: opened product files, selected product file, available bands in selected product, the selected band, the displayed views, the selected view may serve as input to the tool. In case of the GPF operator, inputs are provided by standard mechanisms used by the GPT and are already implemented in SNAP: inputs come from XML configuration files or from command-line parameters.

Invoke the tool so that a new process is created

Notify the user about the progress and eventually let her/him cancel the running process

The output of the tool while it is running, for example logging information, is converted to a progress indication for the user. In the case of invocation from the Toolbox GUI, the user can see a progress bar and can cancel the operation in case of long-running processes.

Open the generated outputs in the Toolbox.

If the tool is invoked from the Toolbox GUI and the output is readable by the Toolbox, the resulting product is opened so that the user can visualise the result. If the tool is invoked from a GPF operator, the output of the adapter operator can serve as input to a subsequent processing step.

See here for a description of the user interface as well as the parameters that can be used to integrate an external tool (executable or script).