TIL Day 28

2023.10.27

Today's agenda

1. template matching
2. pararrel in opencv

1. template matching

find part from source image to template image

void matchTemplate(InputArray image, InputArray templ,
					OutputArray result, int method, InputArray mask = noArray());

parameters

• image : input image(CV_8UC1 or CV_32F1)
• templ : template image
• result : CV_32F1 matrix
• method :
• mask : mask image

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

using namespace std;
using namespace cv;

int main()
{
	Mat src = imread("circuit.bmp", IMREAD_GRAYSCALE);
	Mat tmpl = imread("crystal.bmp", IMREAD_GRAYSCALE);

#if 0
	src = imread("wheres_wally.jpg", IMREAD_GRAYSCALE); // IMREAD_COLOR
	tmpl = imread("wally.bmp", IMREAD_GRAYSCALE);
#endif

	if (src.empty() || tmpl.empty()) {
		cerr << "Image load failed!" << endl;
		return -1;
	}

#if 1
	src = src + 50;

	Mat noise(src.size(), CV_32S);
	randn(noise, 0, 10); // 10, 50, 100
	add(src, noise, src, noArray(), CV_8U);
#endif

#if 1
	GaussianBlur(src, src, Size(), 1);
	GaussianBlur(tmpl, tmpl, Size(), 1);
#endif

#if 0
	resize(src, src, Size(), 0.9, 0.9); // 0.8, 0.7
#endif

#if 0
	Point2f cp(src.cols / 2.f, src.rows / 2.f);
	Mat rot = getRotationMatrix2D(cp, 10, 1); // 20, 30
	warpAffine(src, src, rot, src.size());
#endif

	Mat res, res_norm;
	matchTemplate(src, tmpl, res, TM_CCOEFF_NORMED);
	normalize(res, res_norm, 0, 255, NORM_MINMAX, CV_8U);

	double maxv;
	Point maxloc;
	minMaxLoc(res, 0, &maxv, 0, &maxloc);

	cout << "maxv: " << maxv << endl;
	cout << "maxloc: " << maxloc << endl;

	Mat dst;
	cvtColor(src, dst, COLOR_GRAY2BGR);

	rectangle(dst, Rect(maxloc.x, maxloc.y, tmpl.cols, tmpl.rows), Scalar(0, 0, 255), 2);

//	imshow("src", src);
	imshow("tmpl", tmpl);
	imshow("res_norm", res_norm);
	imshow("dst", dst);
	waitKey();
}

if more than 1 template is exist in source image

matchTemplate(src, tmpl, res, TM_CCOEFF_NORMED);
normalize(res, res_norm, 0, 255, NORM_MINMAX, CV_8UC1);

2. pararrel in opencv

supported pararrel method in opencv

void pararrel_for_(const Range& range,
					const PararrelLoopBody& body, double nstripes = -1.);
void pararrel_for_(const Range& range,
					std::function<void(const Range&)> function, double nstripes = -1.);

parameters

• range : ranged for pararrel processing
• body : function body(lambda expression in modern c++)