Multispectral.cxx 6.12 KB
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/*
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 * Copyright (C) 2005-2019 Centre National d'Etudes Spatiales (CNES)
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 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
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/* Example usage:
./Multispectral Input/qb_RoadExtract.tif Output/qb_blue.tif Output/qb_shiftscale.tif
*/

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//  First, we are going to use \doxygen{otb}{VectorImage} instead of the now
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// traditional \doxygen{otb}{Image}. So we include the required header:
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// We also include some other header which will be useful later. Note that we
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// are still using the \doxygen{otb}{Image} in this example for some of the
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// output.

#include "otbImageFileReader.h"
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#include "otbImageFileWriter.h"
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#include "otbMultiToMonoChannelExtractROI.h"
#include "itkShiftScaleImageFilter.h"
#include "otbPerBandVectorImageFilter.h"

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int main(int argc, char* argv[])
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{
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  if (argc != 4)
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  {
    std::cerr << "Usage: " << argv[0] << " <input_filename> <output_extract> <output_shifted_scaled>" << std::endl;
  }

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  // We want to read a multispectral image so we declare the image type and the
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  // reader. As we have done in the previous example we get the filename from
  // the command line.

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  using PixelType       = unsigned short;
  using VectorImageType = otb::VectorImage<PixelType, 2>;
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  using ReaderType           = otb::ImageFileReader<VectorImageType>;
  ReaderType::Pointer reader = ReaderType::New();
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  reader->SetFileName(argv[1]);
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  //  Sometime, you need to process only one spectral band of the image. To get
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  // only one of the spectral band we use the
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  // \doxygen{otb}{MultiToMonoChannelExtractROI}. The declaration is as usual:
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  using ExtractChannelType                   = otb::MultiToMonoChannelExtractROI<PixelType, PixelType>;
  ExtractChannelType::Pointer extractChannel = ExtractChannelType::New();
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  //  We need to pass the parameters to the filter for the extraction. This
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  // filter also allow extracting only a spatial subset of the image. However,
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  // we will extract the whole channel in this case.
  //
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  // To do that, we need to pass the desired region using the
  // \code{SetExtractionRegion()} (method such as \code{SetStartX},
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  // \code{SetSizeX} are also available). We get the region from the reader with
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  // the \code{GetLargestPossibleRegion()} method. Before doing that we need to
  // read the metadata from the file: this is done by calling the
  // \code{UpdateOutputInformation()} on the reader's output. The difference with the
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  // \code{Update()} is that the pixel array is not allocated (yet !) and reduce
  // the memory usage.
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  reader->UpdateOutputInformation();
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  extractChannel->SetExtractionRegion(reader->GetOutput()->GetLargestPossibleRegion());
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  //  We chose the channel number to extract (starting from 1) and we plug the
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  // pipeline.
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  extractChannel->SetChannel(3);
  extractChannel->SetInput(reader->GetOutput());
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  //  To output this image, we need a writer. As the output of the
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  // \doxygen{otb}{MultiToMonoChannelExtractROI} is a \doxygen{otb}{Image}, we
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  // need to template the writer with this type.
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  using ImageType            = otb::Image<PixelType, 2>;
  using WriterType           = otb::ImageFileWriter<ImageType>;
  WriterType::Pointer writer = WriterType::New();
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  writer->SetFileName(argv[2]);
  writer->SetInput(extractChannel->GetOutput());
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  writer->Update();
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  // After this, we have a one band image that we can process with most OTB
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  // filters.
  //
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  // In some situation, you may want to apply the same process to all bands of
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  // the image. You don't have to extract each band and process them separately.
  // There is several situations:
  //
  // \begin{itemize}
  // \item the filter (or the combination of filters) you want to use are doing
  // operations that are well defined for \doxygen{itk}{VariableLengthVector}
  // (which is the pixel type), then you don't have to do anything special.
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  // \item if this is not working, you can look for the equivalent filter
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  // specially designed for vector images.
  // \item some of the filter you need to use applies operations undefined for
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  // \doxygen{itk}{VariableLengthVector}, then you can use the
  // \doxygen{otb}{PerBandVectorImageFilter} specially designed for this
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  // purpose.
  // \end{itemize}
  //
  // Let's see how this filter is working. We chose to apply the
  // \doxygen{itk}{ShiftScaleImageFilter} to each of the spectral band. We start
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  // by declaring the filter on a normal \doxygen{otb}{Image}. Note that we
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  // don't need to specify any input for this filter.
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  using ShiftScaleType               = itk::ShiftScaleImageFilter<ImageType, ImageType>;
  ShiftScaleType::Pointer shiftScale = ShiftScaleType::New();
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  shiftScale->SetScale(0.5);
  shiftScale->SetShift(10);
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  // We declare the \doxygen{otb}{PerBandVectorImageFilter} which has three
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  // template: the input image type, the output image type and the filter type
  // to apply to each band.
  //
  // The filter is selected using the \code{SetFilter()} method and the input
  // by the usual \code{SetInput()} method.
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  using VectorFilterType                 = otb::PerBandVectorImageFilter<VectorImageType, VectorImageType, ShiftScaleType>;
  VectorFilterType::Pointer vectorFilter = VectorFilterType::New();
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  vectorFilter->SetFilter(shiftScale);
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  vectorFilter->SetInput(reader->GetOutput());
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  // Now, we just have to save the image using a writer templated over an
  // \doxygen{otb}{VectorImage}:
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  using VectorWriterType                 = otb::ImageFileWriter<VectorImageType>;
  VectorWriterType::Pointer writerVector = VectorWriterType::New();
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  writerVector->SetFileName(argv[3]);
  writerVector->SetInput(vectorFilter->GetOutput());
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  writerVector->Update();
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  return EXIT_SUCCESS;
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}