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
intihist[256]; //
图像直方图,256个点
int i,
j,k; //
various counters
int n, n1, n2, gmin, gmax;
double m1, m2, sum, csum, fmax, sb;
// 对直方图置零...
memset(ihist, 0, sizeof(ihist));
gmin=255; gmax=0;
// 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++;
}
}
// set up everything
sum = csum = 0.0;
n = 0;
for (k = 0; k <= 255; k++)
{
sum
+=(double) k *
(double)ihist[k];
n
+=ihist[k];
}
if (!n) {
// if n
hasno value, there is problems...
fprintf(stderr, "NOT NORMAL thresholdValue = 160\n");
return(160);
}
// do the otsu global
thresholdingmethod
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);
if (sb
>fmax) {
fmax
= sb;
thresholdValue
= k;
}
}
// at this point we have our
thresholdingvalue
// debug code to display
thresholdingvalues
if ( vvv & 1 )
fprintf(stderr,"# OTSU: thresholdValue =
%dgmin=%d gmax=%d\n",
thresholdValue,
gmin, gmax);
return(thresholdValue);
}
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