/** Author: Andre Beinrucker (andre.beinrucker@uni-potsdam.de)

//This is a very crude edge detector, inspired by the one described in www.idiap.ch/~fleuret/papers/fleuret-jmlr2004.pdf (Figure 3)

*/

#include <mash/heuristic.h>
#include <math.h>
using namespace Mash;


//------------------------------------------------------------------------------
/// The 'Identity' heuristic class
//------------------------------------------------------------------------------
class simple_edgedetector: public Heuristic
{
    //_____ Construction / Destruction __________
public:
    simple_edgedetector();
    virtual ~simple_edgedetector();


    //_____ Implementation of Heuristic __________
public:
    virtual unsigned int dim();

    virtual scalar_t computeFeature(unsigned int feature_index);
};


//------------------------------------------------------------------------------
/// Creation function of the heuristic
//------------------------------------------------------------------------------
extern "C" Heuristic* new_heuristic()
{
    return new simple_edgedetector();
}



/************************* CONSTRUCTION / DESTRUCTION *************************/

simple_edgedetector::simple_edgedetector()
{
}


simple_edgedetector::~simple_edgedetector()
{
}


/************************* IMPLEMENTATION OF Heuristic ************************/

unsigned int simple_edgedetector::dim()
{
    // We have has many features than pixels in the region of interest
    unsigned int roi_size = roi_extent * 2 + 1;
    return roi_size * roi_size;
}


scalar_t simple_edgedetector::computeFeature(unsigned int feature_index)
{
    // Compute the coordinates of the top-left pixel of the region of interest
    unsigned int x0 = coordinates.x - roi_extent;
    unsigned int y0 = coordinates.y - roi_extent;

    // Compute the coordinates of the pixel corresponding to the feature, in
    // the region of interest
    unsigned int roi_size = roi_extent * 2 + 1;
    unsigned int x = feature_index % roi_size;
    unsigned int y = (feature_index - x) / roi_size;

    // Return the pixel value corresponding to the desired feature
    byte_t** pLines = image->grayLines();

    //Detect horizontal edges

    if ((y<roi_size-2) && (x<roi_size-1) && (y>0) && (x>0))
    {
        int horizontal_difference = 0;
        int horizontal_average_of_differences = 0;
        horizontal_difference = ((pLines[y0 + y][x0 + x] - pLines[y0 + y - 1][x0 + x]));
        horizontal_average_of_differences =
        (   fabs(pLines[y0 + y    ][x0 + x - 1] - pLines[y0 + y    ][x0 + x    ]) +
            fabs(pLines[y0 + y    ][x0 + x    ] - pLines[y0 + y    ][x0 + x + 1]) +
            //fabs(pLines[y0 + y - 1][x0 + x    ] - pLines[y0 + y    ][x0 + x    ]) +
            fabs(pLines[y0 + y + 1][x0 + x - 1] - pLines[y0 + y + 1][x0 + x    ]) +
            fabs(pLines[y0 + y + 1][x0 + x    ] - pLines[y0 + y + 1][x0 + x + 1]) //+
            //fabs(pLines[y0 + y + 1][x0 + x    ] - pLines[y0 + y + 2][x0 + x    ])
            );
        if (fabs(horizontal_difference) > 2*fabs(horizontal_average_of_differences))
            return 1.0f;
    }



    return 0.0f;
}