This standalone OTB module is a wrapper of the Sirius library. It provides an image to image filter which resamples an image in the frequency domain. This filter is packaged in the application FrequencyResample.

• Orfeo Toolbox
• Sirius library
• Sirius documentation

This module is using CMake to build its libraries and executables.

• C++14 compiler (GCC >5)
• CMake >=3.2
• GDAL development kit, >=2
• FFTW development kit, >=3
• Sirius library

OTB Frequency Resample Module depends on the Sirius library. In order to find the library using CMake find_package helper, SIRIUS_ROOT must be set to a Sirius install directory.

This OTB module can be built outside the OTB project as a standalone module. It only requires an OTB build tree (e.g. SuperBuild generation).

• CMAKE_BUILD_TYPE: Debug, Release, RelWithDebInfo and MinSizeRel
• SIRIUS_ROOT: path to Sirius install directory
• OTB_BUILD_MODULE_AS_STANDALONE: set to ON to build FrequencyResample as a standalone module
• OTB_DIR: path to the OTB build tree CMake directory
• BUILD_TESTING: set to ON to enable tests

git clone https://github.com/CS-SI/OTB-SIRIUS.git
mkdir .build
cd .build
cmake .. -DCMAKE_BUILD_TYPE=Release \
         -DSIRIUS_ROOT=/path/to/Sirius/install/directory \
         -DOTB_BUILD_MODULE_AS_STANDALONE=ON \
         -DOTB_DIR=/path/to/OTB/SDK/lib/cmake/OTB-x.y \
         -DBUILD_TESTING=ON
cmake --build . --target FrequencyResample-all

This module can also be built inside the OTB project (cf. OTB documentation).

• Module_FrequencyResample: set to ON to activate FrequencyResample remote module
• SIRIUS_ROOT: path to Sirius install directory

git clone https://github.com/CS-SI/OTB-SIRIUS.git FrequencyResample
cp -r FrequencyResample /path/to/OTB/Modules/Remote
cd /path/to/OTB/build/directory
cmake /path/to/OTB -DModule_FrequencyResample=ON -DSIRIUS_ROOT=/path/to/Sirius/install/directory
cmake --build . --target FrequencyResample-all

• GDAL library
• FFTW3 library

The following example will zoom in /path/to/input/image.tif by 2, apply the filter /path/to/filter/image.tif to the resampled image and write the output into /path/to/output/image.tif.

# CWD is the OTB build directory
./bin/otbcli_FrequencyResample \
    -in /path/to/input/image.tif \
    -out /path/to/output/image.tif \
    -resampling.ratio 2:1 \
    -filter.path /path/to/filter/image.tif

The following code is a boilerplate to create and initialize the FrequencyResampleFilter component.

#include "otbFrequencyResampleFilter.h"

using FilterType = otb::FrequencyResampleFilter<DoubleImageType>;

// initialization parameters
sirius::ZoomRatio zoom_ratio(2, 1);

sirius::Image filter_image = {...};
sirius::Filter freq_filter = sirius::Filter::Create(filter_image, zoom_ratio);

sirius::ImageDecompositionPolicies image_decomposition =
      sirius::ImageDecompositionPolicies::kRegular;
sirius::FrequencyZoomStrategies zoom_strategy =
      sirius::FrequencyZoomStrategies::kPeriodization;

FilterType::Pointer i2i_filter = FilterType::New();

// init filter
i2i_filter->Init(zoom_ratio, std::move(freq_filter),
                 image_decomposition, zoom_strategy);

i2i_filter->SetInput(...);