FeatureExtractor.h

/*******************************************
 FeatureExtractor base class.
 *******************************************/

#ifndef FEATURE_EXTRACTOR_HEADER
#define FEATURE_EXTRACTOR_HEADER

#include "Feature.h"

typedef unsigned char uchar;

class FeatureExtractor {
public:
    // Interface.
    virtual void Extract(int width, int height, int i, int j, Feature *feature) = 0;

    // Some preprocess work, such as integral image.
    virtual void Preprocess(const cv::Mat& img) {}
};

// Extract a HoG feature.
// Use integral image to accelerate.
class HoGExtractor : public FeatureExtractor {
public:
    HoGExtractor(int width, int height);

    void Preprocess(const cv::Mat& img);

    // Use the integral image to extract HoG.
    // Must be called after Preprocess.
    void Extract(int width, int height, int i, int j, Feature *feature);

    ~HoGExtractor();

private:
    static const float xVector[9];
    static const float yVector[9];

    inline int Direct(feat x, feat y) {
        feat max = 0.0;
        int ret = 0;
        for (int i = 0; i < 9; i++) {
            feat proj = ABS(x * xVector[i] + y * yVector[i]);
            if (proj > max) {
                max = proj;
                ret = i;
            }
        }
        return ret;
    }

    feat *integrals;
    feat *bins;
    int widthStep;
};

#endif