13 OpenCV基本阈值操作threshold

一、基本阈值操作

opencv提供了threshold()函数对图像的阈值进行处理，threshold()共支持五种类型的阈值化方式，分别是阈值二值化、阈值反二值化、截断、阈值取零和阈值反取零。

• 阈值二值化 threshold binary
  
• 阈值反二值化 threshold binary inverted
  
• 截断 truncate
  
• 阈值取零 threshold to zero
  
• 阈值反取零 threshold to zero inverted
  

二、threshold()

double cv::threshold  ( InputArray  src,  
  OutputArray  dst,  
  double  thresh,  
  double  maxval,  
  int  type  
 ) 

• InputArray src: 输入图像，可以是Mat类型，图像必须为单通道8位或32位浮点型图像
• OutputArray dst: 输出图像，与输入图像尺寸和类型相同
• double thresh: 设定的阈值
• double maxval: 使用THRESH_BINARY和THRESH_BINARY_INV类型的最大值
• int type: 阈值化类型

三、示例

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

Mat src, dst, gray_src;
int threshold_value = 127;
int threshold_max = 255;

const char* output_title = "binary image";
void Threshold_Demo(int, void*);

int main()
{
	src = imread("images/02.png");
	if (!src.data) {
		cout << "could not load image1..." << endl;
		return -1;
	}
	namedWindow("input_image", CV_WINDOW_AUTOSIZE);
	imshow("input_image", src);

	Threshold_Demo(0, 0);
	createTrackbar("Threshold Value:", output_title, &threshold_value, threshold_max, Threshold_Demo);
	

	waitKey();
	return 0;
}
void Threshold_Demo(int, void*)
{
	cvtColor(src, gray_src, CV_BGR2GRAY);
	
	threshold(gray_src, dst, threshold_value,threshold_max,THRESH_BINARY);
	imshow(output_title, dst);
}