二值化ostu算法：
#include "stdafx.h"
#include <stdio.h>
#include <cv.h>
#include <highgui.h>
#include <math.h>
int Otsu(IplImage* src);
int _tmain(int argc, _TCHAR* argv[])
{
IplImage* img = cvLoadImage("Lena.jpg",0);
IplImage* dst = cvCreateImage(cvGetSize(img), 8, 1);
int threshold = Otsu(img);
cvThreshold(img, dst, threshold, 255, CV_THRESH_BINARY);
cvNamedWindow( "img", 1 );
cvShowImage("img", dst);
cvWaitKey(-1);
cvReleaseImage(&img);
cvReleaseImage(&dst);
cvDestroyWindow( "dst" );
return 0;
}
int Otsu(IplImage* src)
{
int height=src->height;
int width=src->width;
long size = height * width;
//histogram
float histogram[256] = {0};
for(int m=0; m < height; m++)
{
unsigned char* p=(unsigned char*)src->imageData + src->widthStep * m;
for(int n = 0; n < width; n++)
{
histogram[int(*p++)]++;
}
}
int threshold;
long sum0 = 0, sum1 = 0; //存储前景的灰度总和和背景灰度总和
long cnt0 = 0, cnt1 = 0; //前景的总个数和背景的总个数
double w0 = 0, w1 = 0; //前景和背景所占整幅图像的比例
double u0 = 0, u1 = 0; //前景和背景的平均灰度
double variance = 0; //最大类间方差
int i, j;
double u = 0;
double maxVariance = 0;
for(i = 1; i < 256; i++) //一次遍历每个像素
{
sum0 = 0;
sum1 = 0;
cnt0 = 0;
cnt1 = 0;
w0 = 0;
w1 = 0;
for(j = 0; j < i; j++)
{
cnt0 += histogram[j];
sum0 += j * histogram[j];
}
u0 = (double)sum0 / cnt0;
w0 = (double)cnt0 / size;
for(j = i ; j <= 255; j++)
{
cnt1 += histogram[j];
sum1 += j * histogram[j];
}
u1 = (double)sum1 / cnt1;
w1 = 1 - w0; // (double)cnt1 / size;
u = u0 * w0 + u1 * w1; //图像的平均灰度
printf("u = %f\n", u);
//variance = w0 * pow((u0 - u), 2) + w1 * pow((u1 - u), 2);
variance = w0 * w1 * (u0 - u1) * (u0 - u1);
if(variance > maxVariance)
{
maxVariance = variance;
threshold = i;
}
}
printf("threshold = %d\n", threshold);
return threshold;
}