Quickstart: running an OTB application with pyotb¶

pyotb has been written so that it is more convenient to run an application in Python.

You can pass the parameters of an application as a dictionary :

import pyotb
resampled = pyotb.RigidTransformResample({'in': 'my_image.tif', 'transform.type.id.scaley': 0.5,
                                          'interpolator': 'linear', 'transform.type.id.scalex': 0.5})

Note that pyotb has a 'lazy' evaluation: it only performs operation when it is needed, i.e. results are written to disk. Thus, the previous line doesn't trigger the application.

To actually trigger the application execution, you need to write the result to disk:

resampled.write('output.tif')  # this is when the application actually runs

Using Python keyword arguments¶

It is also possible to use the Python keyword arguments notation for passing the parameters:

output = pyotb.SuperImpose(inr='reference_image.tif', inm='image.tif')

is equivalent to:

output = pyotb.SuperImpose({'inr': 'reference_image.tif', 'inm': 'image.tif'})

Limitations : for this notation, python doesn't accept the parameter in or any parameter that contains a .. E.g., it is not possible to use pyotb.RigidTransformResample(in=input_path...) or pyotb.VectorDataExtractROI(io.vd=vector_path...).

In-memory connections¶

The big asset of pyotb is the ease of in-memory connections between apps.

Let's start from our previous example. Consider the case where one wants to apply optical calibration and binary morphological dilatation following the undersampling.

Using pyotb, you can pass the output of an app as input of another app :

import pyotb

resampled = pyotb.RigidTransformResample({'in': 'my_image.tif', 'interpolator': 'linear', 
                                          'transform.type.id.scaley': 0.5, 'transform.type.id.scalex': 0.5})

calibrated = pyotb.OpticalCalibration({'in': resampled, 'level': 'toa'}) 

dilated = pyotb.BinaryMorphologicalOperation({'in': calibrated, 'out': 'output.tif', 'filter': 'dilate', 
                                              'structype': 'ball', 'xradius': 3, 'yradius': 3})
dilated.write('result.tif')

Writing the result of an app¶

Any pyotb object can be written to disk using the write method, e.g. :

import pyotb

resampled = pyotb.RigidTransformResample({'in': 'my_image.tif', 'interpolator': 'linear',
                                          'transform.type.id.scaley': 0.5, 'transform.type.id.scalex': 0.5})
# Here you can set optionally pixel type and extended filename variables
resampled.write({'out': 'output.tif'}, pixel_type='uint16', filename_extension='?nodata=65535')

Another possibility for writing results is to set the output parameter when initializing the application:

import pyotb

resampled = pyotb.RigidTransformResample({'in': 'my_image.tif', 'interpolator': 'linear', 'out': 'output.tif',
                                          'transform.type.id.scaley': 0.5, 'transform.type.id.scalex': 0.5})
# Here you can set optionally pixel type and extended filename variables
resampled.write(pixel_type='uint16', filename_extension='?nodata=65535')