Commit 456976fc authored by Guillaume Pasero's avatar Guillaume Pasero
Browse files

DOC: document switch for application connection in CooBook

parent c6083ff4
......@@ -218,6 +218,68 @@ implementation does not break it, for instance by using an internal
writer to write intermediate data. In this case, execution should
still be correct, but some intermediate data will be read or written.
Mixed in-memory / on-disk connection
As an extension to the connection of OTB Applications (described in previous
section), a mixed mode is also available to easily switch between:
- **in-memory**: if you want to avoid unecessary I/O between applications
- **on-disk**: if you want intermediate outputs on disk
This mixed mode is based on the ``Application::ConnectImage()`` function. This
is how you use it:
.. code-block:: python
# for in-memory mode
app1 = otb.Registry.CreateApplication("Smoothing")
app2 = otb.Registry.CreateApplication("Smoothing")
app1.IN = input_image
app2.ConnectImage("in", app1, "out")
app2.OUT = output_image
Comparing with the standard in-memory connection, you can notice that:
- the syntax to do the connection is simpler
- you don't need to call ``Execute()`` on upstream applications anymore,
this is done recursively by calling ``ExecuteAndWriteOutput()`` on the latest
The on-disk version of this code is very similar:
.. code-block:: python
# for on-disk mode
app1 = otb.Registry.CreateApplication("Smoothing")
app2 = otb.Registry.CreateApplication("Smoothing")
app1.IN = input_image
app1.OUT = temp_image
app2.ConnectImage("in", app1, "out")
app2.OUT = output_image
The function ``PropagateConnectMode()`` is applied recursively in the upstream
applications. It allows to change between the 2 modes:
- ``True`` : means in-memory mode (this is the default)
- ``False`` : means on-disk mode
When you want to use the on-disk mode, you have to specify the path to
the intermediate image in the **output** image parameter of the upstream
application (``app1.OUT`` in the previous example). If this path is empty, the
in-memory mode is used as fallback.
This feature also works for ``InputImageList``. Calling the function
``ConnectImage("il", app1, "out")``, with ``il`` being an input image list, will
append a new image to the list, and connect it to output parameter ``out``.
Load and save parameters to XML
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