SimpleBackgroundAnalyzer.cpp

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/*
 * Background.cpp
 *
 *  Created on: Oct 11, 2016
 *      Author: mschefer
 */
 
#include "SEFramework/Image/ImageAccessor.h"
#include "SEImplementation/Background/Utils.h"
#include "SEImplementation/Background/SimpleBackgroundAnalyzer.h"
 
#include <memory>
#include <algorithm>
 
#include "SEFramework/Image/ConstantImage.h"
#include "SEFramework/Image/VectorImage.h"
#include "SEFramework/Image/ProcessedImage.h"
 
 
namespace SourceXtractor {
 
BackgroundModel SimpleBackgroundAnalyzer::analyzeBackground(
    std::shared_ptr<DetectionImage> image,
    std::shared_ptr<WeightImage> /*variance_map*/, std::shared_ptr<Image<unsigned char>> /*mask*/,
    WeightImage::PixelType /*variance_threshold*/) const {
 
  // FIXME we use a VectorImage the same size as input which won't allow larger than memory images to be processed
 
  auto image_copy = VectorImage<DetectionImage::PixelType>::create(*image);
  std::sort(image_copy->getData().begin(), image_copy->getData().end());
  bck_model_logger.debug() << "Using the SimpleBackgroundLeverAnalyzer";
 
  auto background_level = image_copy->getData()[image_copy->getData().size()/2]; // the median
  auto background_level_map = ConstantImage<SeFloat>::create(image->getWidth(), image->getHeight(), background_level);
 
  auto subtracted_image = SubtractImage<SeFloat>::create(image, background_level_map);
 
  auto background_variance = getVariance(subtracted_image);
  auto background_variance_map = ConstantImage<SeFloat>::create(image->getWidth(), image->getHeight(), background_variance);
  bck_model_logger.debug() << "bg: " << background_level << " var: " << background_variance;
 
  return BackgroundModel(background_level_map, background_variance_map, 1.0, std::sqrt(background_variance));
}
 
 
SeFloat SimpleBackgroundAnalyzer::getVariance(std::shared_ptr<DetectionImage> image) {
  // Note: We compute the RMS by only taking into consideration pixels
  // below the background value.
  using Accessor = ImageAccessor<DetectionImage::PixelType>;
  Accessor accessor(image, Accessor::TOP_LEFT, 256, 1);
 
  double variance = 0;
  int pixels = 0;
  for (int y = 0; y < accessor.getHeight(); y++) {
    for (int x = 0; x < accessor.getWidth(); x++) {
      auto value = accessor.getValue(x, y);
      if (value < 0) {
        variance += value * value;
        pixels++;
      }
    }
  }
 
  if (pixels > 0) {
    variance /= pixels;
  }
 
  return variance;
}
 
}