动态阙值

int ihist[256] = {0}; // 图像直方图，256个点

int otsu (unsigned char *image, int rows, int cols, int x0, int y0, int dx, int dy, int vvv)

{   

	unsigned char *np; // 图像指针

	int thresholdValue=1; // 阈值



	int i, j, k; // various counters

	int n, n1, n2, gmin, gmax;

	double m1, m2, sum, csum, fmax, sb;

		

	//初始化灰度直方图

//	for (k = 0; k <= 255; k++) 

//	{

//		ihist[k] = 0;

//	}

	//gmin=255; gmax=0;//图像阈值范围设置初始

	gmin=200; gmax=60;

	// 生成直方图

	for (i = y0 + 1; i < y0 + dy - 1; i++) {

	   np = &image[i*cols+x0+1];

	   for (j = x0 + 1; j < x0 + dx - 1; j++) {

		   ihist[*np]++;

		   if(*np > gmax) gmax=*np;

		   if(*np < gmin) gmin=*np;

		   np++; /* next pixel */

	   }

	}



	// set up everything

	sum = csum = 0.0;

	n = 0;



	for (k = 0; k <= 255; k++) {

	   sum += (double) k * (double) ihist[k]; /* x*f(x) 质量矩*/

	   n += ihist[k]; /* f(x) 质量 */

	}



	if (!n) {

	   // if n has no value, there is problems...

//	   fprintf (stderr, "NOT NORMAL thresholdValue = 160\n");

	   return (160);

	}



	// do the otsu global thresholding method

	fmax = -1.0;

	n1 = 0;

	for (k = 0; k < 255; k++) {

	   n1 += ihist[k];

	   if (!n1) { continue; }

	   n2 = n - n1;

	   if (n2 == 0) { break; }

	   csum += (double) k *ihist[k];

	   m1 = csum / n1;

	   m2 = (sum - csum) / n2;

	   sb = (double) n1 *(double) n2 *(m1 - m2) * (m1 - m2);

	   /* bbg: note: can be optimized. */

	   if (sb > fmax) {

		   fmax = sb;

		   thresholdValue = k;

	   }

	}



	return(thresholdValue);

}