AutoThreshold (Otsu) C++

Java -> C++

 

Code

int Otsu(float* histo, int n_length) 
{
	// Otsu's threshold algorithm
	// M. Emre Celebi 6.15.2007, Fourier Library https://sourceforge.net/projects/fourier-ipal/
	// ported to ImageJ plugin by G.Landini

	int ih;
	int threshold = -1;
	int num_pixels = 0;
	double total_mean;	/* mean gray-level for the whole image */
	double bcv, term;	/* between-class variance, scaling term */
	double max_bcv;		/* max BCV */
	double* cnh = nullptr;
	double* mean = nullptr;
	double* normal_histo = nullptr;
	
	cnh = new  double[n_length];			/* cumulative normalized histogram */
	mean = new  double[n_length];			/* mean gray-level */
	normal_histo = new  double[n_length];	/* normalized histogram */

	/* Calculate total numbre of pixels */
	for (ih = 0; ih < n_length; ih++)
		num_pixels = num_pixels + histo[ih];

	term = 1.0 / (double)num_pixels;

	/* Calculate the normalized histogram */
	for (ih = 0; ih < n_length; ih++) {
		normal_histo[ih] = term * histo[ih];
	}

	/* Calculate the cumulative normalized histogram */
	cnh[0] = normal_histo[0];
	for (ih = 1; ih < n_length; ih++) {
		cnh[ih] = cnh[ih - 1] + normal_histo[ih];
	}

	mean[0] = 0.0;

	for (ih = 0 + 1; ih < n_length; ih++) {
		mean[ih] = mean[ih - 1] + ih * normal_histo[ih];
	}

	total_mean = mean[n_length - 1];

	//	Calculate the BCV at each gray-level and find the threshold that maximizes it 
	threshold = -DBL_MAX;
	max_bcv = 0.0;

	for (ih = 0; ih < n_length; ih++) {
		bcv = total_mean * cnh[ih] - mean[ih];
		bcv *= bcv / (cnh[ih] * (1.0 - cnh[ih]));

		if (max_bcv < bcv) {
			max_bcv = bcv;
			threshold = ih;
		}
	}

	if (cnh)
		delete[] cnh;

	if (mean)
		delete[] mean;

	if (normal_histo)
		delete[] normal_histo;

	return threshold;
}

 

imageJ 관련 문서 : https://imagej.net/plugins/auto-threshold

github link : https://github.com/fiji/Auto_Threshold/blob/master/src/main/java/fiji/threshold/Auto_Threshold.java