RightAngleDetectionExample.cxx

Example usage:

./RightAngleDetectionExample Input/Scene.png Output/rightAngleOutput.shp 0.1 20

Example source code (RightAngleDetectionExample.cxx):

#include "otbImageFileReader.h"
#include "otbLineSegmentDetector.h"
#include "otbVectorDataFileWriter.h"




// This example illustrates the use of the
// \doxygen{otb}{VectorDataToRightAngleVectorDataFilter}.
// This filter detects the right angles in an image by exploiting the
// output of a line detection algorithm. Typically the
// \doxygen{otb}{LineSegmentDetector} class will be used. The right
// angle detection algorithm is described in detail in
// \cite{RightAngleDetection}.
//
// The first step required to use this filter is to include its header file.

#include "otbVectorDataToRightAngleVectorDataFilter.h"

int main(int argc, char* argv[])
{
  if (argc != 5)
  {
    std::cerr << "Usage: ./RightAngleDetectionExample input rightAngleOutput angleThreshold distanceThreshold\n";
    return EXIT_FAILURE;
  }

  const char* infname                  = argv[1];
  const char* rightAngleOutputFilename = argv[2];
  double      angleThreshold           = atof(argv[3]);
  double      distanceThreshold        = atof(argv[4]);

  const unsigned int Dimension = 2;
  using PixelType              = unsigned char;
  using PrecisionType          = double;

  using ImageType  = otb::Image<PixelType, Dimension>;
  using ReaderType = otb::ImageFileReader<ImageType>;

  auto reader = ReaderType::New();
  reader->SetFileName(infname);
  reader->GenerateOutputInformation();

  // After defining, as usual, the types for the input image and the
  // image reader, we define the specific types needed for this
  // example. First of all, we will use a vector data
  // to store the detected lines which will be provided by the line
  // segment detector.

  using VectorDataType = otb::VectorData<PrecisionType>;
  // The right angle detector's output is a vector data where each point
  // gives the coordinate of the detected angle.
  //
  // Next, We define the type for the line segment detector. A detailed
  // example for this detector can be found in section \ref{sec:LSD}.

  using LsdFilterType = otb::LineSegmentDetector<ImageType, PrecisionType>;

  // We can finally define the type for the right angle detection
  // filter. This filter is templated over the input vector data type
  // provided by the line segment detector.

  using RightAngleFilterType = otb::VectorDataToRightAngleVectorDataFilter<VectorDataType>;

  // We instantiate the line segment detector and the right angle detector.

  auto lsdFilter        = LsdFilterType::New();
  auto rightAngleFilter = RightAngleFilterType::New();

  // We plug the pipeline.

  lsdFilter->SetInput(reader->GetOutput());
  rightAngleFilter->SetInput(lsdFilter->GetOutput());

  // You can choose how far the right angle segments can be, and the tolerance
  // to consider an angle between two segments as an right one.

  rightAngleFilter->SetAngleThreshold(angleThreshold);
  rightAngleFilter->SetDistanceThreshold(distanceThreshold);

  using WriterType = otb::VectorDataFileWriter<LsdFilterType::VectorDataType>;

  auto rightAngleWriter = WriterType::New();

  rightAngleWriter->SetInput(rightAngleFilter->GetOutput());
  rightAngleWriter->SetFileName(rightAngleOutputFilename);

  // Before calling the \code{Update()} method of the writers in order to
  // trigger the pipeline execution, we call the
  // \code{GenerateOutputInformation()} of the reader, so the
  // filter gets the information about image size and spacing.

  reader->GenerateOutputInformation();
  rightAngleWriter->Update();

  return EXIT_SUCCESS;
}