colorhistogram.cpp

#include "colorhistogram.h"

ColorHistogram::ColorHistogram()
{
    histSize[0] = histSize[1] = histSize[2] = 256;
    hranges[0] = 0.0;
    hranges[1] = 255.0;
    ranges[0] = hranges;
    ranges[1] = hranges;
    ranges[2] = hranges;
    channels[0] = 0;
    channels[1] = 1;
    channels[2] = 2;
}

Mat ColorHistogram::getHistogram(const Mat &image)
{
    MatND hist;
    hranges[0] = 0.0;
    hranges[1] = 255.0;
    channels[0] = 0;
    channels[1] = 1;
    channels[2] = 2;
    calcHist(&image,
             1,
             channels,
             Mat(),
             hist,
             3,
             histSize,
             ranges);
    return hist;
}
cv::SparseMat ColorHistogram::getSparseHistogram(const cv::Mat &image) {

        cv::SparseMat hist(3,histSize,CV_32F);

        // BGR color histogram
        hranges[0]= 0.0;    // BRG range
        hranges[1]= 255.0;
        channels[0]= 0;		// the three channels
        channels[1]= 1;
        channels[2]= 2;

        // Compute histogram
        cv::calcHist(&image,
            1,			// histogram of 1 image only
            channels,	// the channel used
            cv::Mat(),	// no mask is used
            hist,		// the resulting histogram
            3,			// it is a 3D histogram
            histSize,	// number of bins
            ranges		// pixel value range
        );

        return hist;
    }
// Computes the 2D ab histogram.
// BGR source image is converted to Lab
cv::MatND ColorHistogram::getabHistogram(const cv::Mat &image) {

    cv::MatND hist;

    // Convert to Lab color space
    cv::Mat lab;
    cv::cvtColor(image, lab, CV_BGR2Lab);

    // Prepare arguments for a 2D color histogram
    hranges[0]= -128.0;
    hranges[1]= 127.0;
    channels[0]= 1; // the two channels used are ab
    channels[1]= 2;

    // Compute histogram
    cv::calcHist(&lab,
        1,			// histogram of 1 image only
        channels,	// the channel used
        cv::Mat(),	// no mask is used
        hist,		// the resulting histogram
        2,			// it is a 2D histogram
        histSize,	// number of bins
        ranges		// pixel value range
    );

    return hist;
}

// Computes the 1D Hue histogram with a mask.
// BGR source image is converted to HSV
cv::MatND ColorHistogram::getHueHistogram(const cv::Mat &image) {

    cv::MatND hist;

    // Convert to Lab color space
    cv::Mat hue;
    cv::cvtColor(image, hue, CV_BGR2HSV);

    // Prepare arguments for a 1D hue histogram
    hranges[0]= 0.0;
    hranges[1]= 180.0;
    channels[0]= 0; // the hue channel

    // Compute histogram
    cv::calcHist(&hue,
        1,			// histogram of 1 image only
        channels,	// the channel used
        cv::Mat(),	// no mask is used
        hist,		// the resulting histogram
        1,			// it is a 1D histogram
        histSize,	// number of bins
        ranges		// pixel value range
    );

    return hist;
}

cv::Mat ColorHistogram::colorReduce(const cv::Mat &image, int div) {

  int n= static_cast<int>(log(static_cast<double>(div))/log(2.0));
  // mask used to round the pixel value
  uchar mask= 0xFF<<n; // e.g. for div=16, mask= 0xF0

  cv::Mat_<cv::Vec3b>::const_iterator it= image.begin<cv::Vec3b>();
  cv::Mat_<cv::Vec3b>::const_iterator itend= image.end<cv::Vec3b>();

  // Set output image (always 1-channel)
  cv::Mat result(image.rows,image.cols,image.type());
  cv::Mat_<cv::Vec3b>::iterator itr= result.begin<cv::Vec3b>();

  for ( ; it!= itend; ++it, ++itr) {

    (*itr)[0]= ((*it)[0]&mask) + div/2;
    (*itr)[1]= ((*it)[1]&mask) + div/2;
    (*itr)[2]= ((*it)[2]&mask) + div/2;
  }

  return result;
}