utils.h

#ifndef __UTILS_H__
#define __UTILS_H__

#include <string>
#include <vector>
#include <set>
#include <sstream>
#include <stdexcept>

// COLORS
const cv::Scalar BLUE(255, 0, 0), 	    RED(0, 0, 255),        GREEN(0, 255, 0),
				 CYAN(255, 255, 0), 	MAGENTA(255, 0, 255),  YELLOW(0, 255, 255),
				 WHITE(255, 255, 255), 	BLACK(0, 0, 0);

inline int pow2(int n) { return 1 << n; }

template<typename T>
inline T sq(T n) { return n * n; }

template<typename T>
inline T lerp(const T& val1, const T& val2, double alpha) {
	return val1*(1-alpha) + val2*alpha;
}

int random(int min, int max);

template<typename T>
inline cv::Rect_<T> roiAround(T x, T y, T radius) {
    return cv::Rect_<T>(x - radius, y - radius, 2*radius + 1, 2*radius + 1);
}

template<typename T>
inline cv::Rect_<T> roiAround(const cv::Point_<T>& centre, T radius)
{
    return roiAround(centre.x, centre.y, radius);
}

inline cv::Rect boundingBox(const cv::Mat& img) {
    return cv::Rect(0,0,img.cols,img.rows);
}

inline cv::Point2f normVec(const cv::Point& vec)
{
	float mag = sqrt(vec.x*vec.x + vec.y*vec.y);
    return cv::Point2f(vec.x/mag, vec.y/mag);
}

template<typename T>
std::vector<T> randomSubset(const std::vector<T>& src, typename std::vector<T>::size_type size) {

	if (size > src.size())
		throw std::range_error("Subset size out of range");

	std::vector<T> ret;
	std::set<int> vals;

	for (size_t j = src.size() - size; j < src.size(); ++j) {

		int rand = random(0, j); // generate a random integer in range [0, j]

		if (vals.find(rand) == vals.end())
			ret.push_back(src[rand]);
		else
			ret.push_back(src[j]);
	}

	return ret;
}

// Drawing convenience methods for cross and plus shapes
inline void cross(cv::Mat& img, cv::Point centre, int radius, const cv::Scalar& colour, int thickness = 1, int lineType = 8, int shift = 0) {
    cv::line(img, centre + cv::Point(-radius, -radius), centre + cv::Point(radius, radius), colour, thickness, lineType, shift = 0);
    cv::line(img, centre + cv::Point(-radius, radius), centre + cv::Point(radius, -radius), colour, thickness, lineType, shift = 0);
}
inline void plus(cv::Mat& img, cv::Point centre, int radius, const cv::Scalar& colour, int thickness = 1, int lineType = 8, int shift = 0) {
    cv::line(img, centre + cv::Point(0, -radius), centre + cv::Point(0, radius), colour, thickness, lineType, shift = 0);
    cv::line(img, centre + cv::Point(-radius, 0), centre + cv::Point(radius, 0), colour, thickness, lineType, shift = 0);
}

#endif // __UTILS_H__