//opencv
#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
/******************************************************************************************
Function: OtsuThreshold
Description: 图片二值化最佳阈值确定（大津法,OTSU算法)
Input: src:原图片
Return: 阈值
******************************************************************************************/
int OtsuThreshold(IplImage* src)
{
int threshold;
try
{
int height = src->height;
int width = src->width;
//histogram
float histogram[256] = { 0 };
for (int i = 0; i < height; i++) {
unsigned char* p = (unsigned char*)src->imageData + src->widthStep*i;
for (int j = 0; j < width; j++) {
histogram[*p++]++;
}
}
//normalize histogram
int size = height*width;
for (int i = 0; i < 256; i++) {
histogram[i] = histogram[i] / size;
}
//average pixel value
float avgValue = 0;
for (int i = 0; i < 256; i++) {
avgValue += i*histogram[i];
}
float maxVariance = 0;
float w = 0, u = 0;
for (int i = 0; i < 256; i++) {
w += histogram[i];
u += i*histogram[i];
float t = avgValue*w - u;
float variance = t*t / (w*(1 - w));
if (variance > maxVariance) {
maxVariance = variance;
threshold = i;
}
}
}
catch (cv::Exception e)
{
}
return threshold;
}
