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| #include <opencv/highgui.h> #include <opencv2/opencv.hpp> #include <cmath>
int OSTU(cv::Mat& src) { int threshold=0; float sigma_temp=0.0f; float sigma_max = 0.0f; int pixel_num = src.rows * src.cols; int pixel_count[256]; float pixel_pro[256];
for(int i=0; i<256; i++) { pixel_count[i] = 0; }
for(int i=0; i < src.rows; i++) { uchar* data = src.ptr<uchar>(i);
for(int j=0; j < src.cols; j++) { pixel_count[data[j]]++; } } for(int i=0; i<256; i++) { pixel_pro[i] = (float)(pixel_count[i]) / (float)(pixel_num); }
for(int i=0; i<256; i++) { float w0=0, w1=0, u0=0, u1=0, u=0; for(int j=0; j<256; j++) { if(j < i) { w0 += pixel_pro[j]; u0 += pixel_pro[j] * j; } else { u1 += pixel_pro[j] * j; } }
sigma_temp = w0 * (1-w0) * pow((u0 - u1), 2); if(sigma_temp > sigma_max) { sigma_max = sigma_temp; threshold = i; } }
return threshold; }
void BinaryImage(cv::Mat& src, cv::Mat& des, int threshold) { for(int i=0; i < src.rows; i++) { uchar* src_data = src.ptr<uchar>(i); uchar* des_data = des.ptr<uchar>(i);
for(int j=0; j < src.cols; j++) { if(src_data[j] < threshold) { des_data[j] = 0; } else { des_data[j] = 255; } } } }
int main() { cv::Mat src, gray;
cv::namedWindow("src", cv::WINDOW_NORMAL); cv::namedWindow("gray", cv::WINDOW_NORMAL); cv::namedWindow("binary", cv::WINDOW_NORMAL);
src = cv::imread("../wallhaven-698240.jpg", cv::IMREAD_COLOR); cv::cvtColor(src, gray, cv::COLOR_RGB2GRAY);
int threshold = OSTU(gray);
cv::Mat binary = cv::Mat(gray.rows, gray.cols, CV_8U); BinaryImage(gray, binary, threshold);
printf("threshold: %d\n", threshold);
cv::imshow("src", src); cv::imshow("gray", gray); cv::imshow("binary", binary);
cv::waitKey(0);
return 0; }
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