OrthoRectificationExample.cxx

Example source code (OrthoRectificationExample.cxx):

#include "otbImageFileReader.h"
#include "otbImageFileWriter.h"

// This example demonstrates the use of the
// \doxygen{otb}{GenericRSResampleImageFilter}. This filter is intended to
// orthorectify images which are in a distributor format with the
// appropriate meta-data describing the sensor model. In this example,
// we will choose to use an UTM projection for the output image.
//
// The first step toward the use of these filters is to include the
// proper header files: the one for the ortho-rectification filter and
// the one defining the different projections available in OTB.

#include "otbGenericRSResampleImageFilter.h"
#include "otbSpatialReference.h"

int main(int argc, char* argv[])
{

  if (argc != 11)
  {
    std::cout << argv[0]
              << " <input_filename> <output_filename>  <utm zone> <hemisphere N/S> <x_ground_upper_left_corner> <y_ground_upper_left_corner> <x_Size> <y_Size> "
                 "<x_groundSamplingDistance> <y_groundSamplingDistance> (should be negative since origin is upper left)>"
              << std::endl;

    return EXIT_FAILURE;
  }

  // We will start by defining the types for the images, the image file
  // reader and the image file writer. The writer will be a
  // \doxygen{otb}{ImageFileWriter} which will allow us to set
  // the number of stream divisions we want to apply when writing the
  // output image, which can be very large.

  using ImageType       = otb::Image<int, 2>;
  using VectorImageType = otb::VectorImage<int, 2>;
  using ReaderType      = otb::ImageFileReader<VectorImageType>;
  using WriterType      = otb::ImageFileWriter<VectorImageType>;

  ReaderType::Pointer reader = ReaderType::New();
  WriterType::Pointer writer = WriterType::New();

  reader->SetFileName(argv[1]);
  writer->SetFileName(argv[2]);

  // We can now proceed to declare the type for the ortho-rectification
  // filter. The class \doxygen{otb}{GenericRSResampleImageFilter} is
  // templated over the input and the output image types.

  // Software Guide : BeginCodeSnippet

  using OrthoRectifFilterType = otb::GenericRSResampleImageFilter<VectorImageType, VectorImageType>;

  OrthoRectifFilterType::Pointer orthoRectifFilter = OrthoRectifFilterType::New();

  // Now we need to
  // instantiate the map projection, set the {\em zone} and {\em hemisphere}
  // parameters and pass this projection to the orthorectification filter.

  std::string wkt =
      otb::SpatialReference::FromUTM(atoi(argv[3]), *argv[4] == 'N' ? otb::SpatialReference::hemisphere::north : otb::SpatialReference::hemisphere::south)
          .ToWkt();
  std::cout << wkt << std::endl;
  orthoRectifFilter->SetOutputProjectionRef(wkt);

  // We then wire the input image to the orthorectification filter.

  orthoRectifFilter->SetInput(reader->GetOutput());

  // Using the user-provided information, we define the output region
  // for the image generated by the orthorectification filter.
  // We also define the spacing of the deformation grid where actual
  // deformation values are estimated. Choosing a bigger deformation field
  // spacing will speed up computation.

  ImageType::IndexType start;
  start[0] = 0;
  start[1] = 0;
  orthoRectifFilter->SetOutputStartIndex(start);

  ImageType::SizeType size;
  size[0] = atoi(argv[7]);
  size[1] = atoi(argv[8]);
  orthoRectifFilter->SetOutputSize(size);

  ImageType::SpacingType spacing;
  spacing[0] = atof(argv[9]);
  spacing[1] = atof(argv[10]);
  orthoRectifFilter->SetOutputSpacing(spacing);

  ImageType::SpacingType gridSpacing;
  gridSpacing[0] = 2. * atof(argv[9]);
  gridSpacing[1] = 2. * atof(argv[10]);
  orthoRectifFilter->SetDisplacementFieldSpacing(gridSpacing);

  ImageType::PointType origin;
  origin[0] = strtod(argv[5], nullptr);
  origin[1] = strtod(argv[6], nullptr);
  orthoRectifFilter->SetOutputOrigin(origin);

  // We can now set plug the ortho-rectification filter to the writer
  // and set the number of tiles we want to split the output image in
  // for the writing step.

  writer->SetInput(orthoRectifFilter->GetOutput());

  // Finally, we trigger the pipeline execution by calling the
  // \code{Update()} method on the writer. Please note that the
  // ortho-rectification filter is derived from the
  // \doxygen{otb}{StreamingResampleImageFilter} in order to be able to
  // compute the input image regions which are needed to build the
  // output image. Since the resampler applies a geometric
  // transformation (scale, rotation, etc.), this region computation is
  // not trivial.

  writer->Update();

  return EXIT_SUCCESS;
}