colorhistogram.h

#if !defined COLHISTOGRAM

#define COLHISTOGRAM

 

#include <opencv2\core\core.hpp>

#include <opencv2\imgproc\imgproc.hpp>

 

class ColorHistogram {

 

 

  private:

 

    int histSize[3];

float hranges[2];

    const float* ranges[3];

    int channels[3];

 

  public:

 

ColorHistogram() {

 

 

// Prepare arguments for a color histogram

histSize[0]= histSize[1]= histSize[2]= 256;

hranges[0]= 0.0;    // BRG range

hranges[1]= 255.0;

ranges[0]= hranges; // all channels have the same range

ranges[1]= hranges;

ranges[2]= hranges;

channels[0]= 0;// the three channels

channels[1]= 1;

channels[2]= 2;

 

}

 

// Computes the histogram.

cv::MatND getHistogram(const cv::Mat &image) {

 

 

cv::MatND hist;

 

// 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 histogram.

cv::SparseMat 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 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 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 colorReduce(const cv::Mat &image, int div=64) {

 

 

  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;

 

}

 

 

};

 

 

#endif