opencv4入门笔记（25）：二值图像与固定阈值分割萤火

本系列代码托管于：https://github.com/chintsan-code/opencv4-tutorials

本篇使用的项目为：bin_image

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

using namespace cv;
using namespace std;

int main(int argc, const char** argv) {
	Mat src = imread("../sample/master.jpg");
	if (src.empty()) {
		cout << "could not load image..." << endl;
		return -1;
	}
	namedWindow("input", WINDOW_AUTOSIZE);
	imshow("input", src);
	Mat gray, binary;
	cvtColor(src, gray, COLOR_BGR2GRAY);
	imshow("input", gray);
	threshold(gray, binary, 200, 255, THRESH_BINARY);
	imshow("threshold binary", binary);

	threshold(gray, binary, 127, 255, THRESH_BINARY_INV);
	imshow("threshold binary invert", binary);

	threshold(gray, binary, 127, 255, THRESH_TRUNC);
	imshow("threshold TRUNC", binary);

	threshold(gray, binary, 127, 255, THRESH_TOZERO);
	imshow("threshold to zero", binary);

	threshold(gray, binary, 127, 255, THRESH_TOZERO_INV);
	imshow("threshold to zero invert", binary);

	waitKey(0);
	destroyAllWindows();
	return 0;
}

灰度与二值图像

灰度图像：单通道。取值范围0-255
二值图像：单通道。取值0（黑色）或255（白色）

threshold：使用固定阈值对图像进行分割

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

src：输入图像。8-bit或32F，多通道
dst：输出图像，与src具有相同的尺寸、类型、通道数
thresh：固定阈值。当type含有THRESH_OTSU或THRESH_TRIANGLE时，可以设为0，即不需要手动设置，而是使用全局自动阈值
maxval：当type为THRESH_BINARY或THRESH_BINARY_INV时使用的最大值
type：分割类型
- THRESH_BINARY
- THRESH_BINARY_INV
- THRESH_TRUNC
- THRESH_TOZERO
- THRESH_TOZERO_INV
- THRESH_OTSU
- THRESH_TRIANGLE
@return：当type含有THRESH_OTSU或THRESH_TRIANGLE时，返回计算出的thresh

关于type：