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#include "precomp.hpp"
#include "opencv2/photo.hpp"
#include "opencv2/imgproc.hpp"
#include "hdr_common.hpp"

namespace cv
{
	
class CalibrateDebevecImpl : public CalibrateDebevec
{
public:
	CalibrateDebevecImpl(int samples, float lambda) :
		samples(samples),
		lambda(lambda),
		name("CalibrateDebevec"),
		w(tringleWeights())
	{
	}
	
	void process(InputArrayOfArrays src, OutputArray dst, std::vector<float>& times)
	{
		std::vector<Mat> images;
		src.getMatVector(images);
		dst.create(256, images[0].channels(), CV_32F);
		Mat response = dst.getMat();

		CV_Assert(!images.empty() && images.size() == times.size());
		CV_Assert(images[0].depth() == CV_8U);
		checkImageDimensions(images);

		for(int channel = 0; channel < images[0].channels(); channel++) {
			Mat A = Mat::zeros(samples * images.size() + 257, 256 + samples, CV_32F);
			Mat B = Mat::zeros(A.rows, 1, CV_32F);

			int eq = 0;
			for(int i = 0; i < samples; i++) {

				int pos = 3 * (rand() % images[0].total()) + channel;
				for(size_t j = 0; j < images.size(); j++) {

					int val = (images[j].ptr() + pos)[0];
					A.at<float>(eq, val) = w.at<float>(val);
					A.at<float>(eq, 256 + i) = -w.at<float>(val);
					B.at<float>(eq, 0) = w.at<float>(val) * log(times[j]);		
					eq++;
				}
			}
			A.at<float>(eq, 128) = 1;
			eq++;

			for(int i = 0; i < 254; i++) {
				A.at<float>(eq, i) = lambda * w.at<float>(i + 1);
				A.at<float>(eq, i + 1) = -2 * lambda * w.at<float>(i + 1);
				A.at<float>(eq, i + 2) = lambda * w.at<float>(i + 1);
				eq++;
			}
			Mat solution;
			solve(A, B, solution, DECOMP_SVD);
			solution.rowRange(0, 256).copyTo(response.col(channel));
		}
		exp(response, response);
	}

	int getSamples() const { return samples; }
	void setSamples(int val) { samples = val; }

	float getLambda() const { return lambda; }
	void setLambda(float val) { lambda = val; }

	void write(FileStorage& fs) const
    {
        fs << "name" << name
		   << "samples" << samples
		   << "lambda" << lambda;
    }

    void read(const FileNode& fn)
    {
        FileNode n = fn["name"];
        CV_Assert(n.isString() && String(n) == name);
        samples = fn["samples"];
		lambda = fn["lambda"];
    }

protected:
	String name;
	int samples;
	float lambda;
	Mat w;
};

Ptr<CalibrateDebevec> createCalibrateDebevec(int samples, float lambda)
{
	return new CalibrateDebevecImpl(samples, lambda);
}

}