第四天：数据结构

声明Point类: PointNX, 例Point2f, Point3f

声明Mat类时, 需要指明数据类型和通道数: CV_{8U,16S,16U,32S,32F,32F,64F}, CV_{1,2,3,(N)}

一大堆函数…

#include <opencv2/opencv.hpp>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include<iostream>
#include<fstream>

using namespace cv;


template <typename T>

void printMatrix(T mat){
	for (size_t i = 0; i < mat.cols; i++)
	{
		for (size_t j = 0; j < mat.rows; j++)
			std::cout<<mat.val[i*mat.rows+j]<<"\t";
		std::cout<<std::endl;
	}
}


int matrixCalc(){
	Matx33f matrix = Matx33f::ones();
	Vec3f vector = Vec3f(3,1,2);
	Vec3f vector2 = matrix*vector;

	printMatrix(vector2);
	
	return 0;
}

计算一个3×3 float matrix 和 1×3 float vector 的点积并用泛型函数打印出结果.

第五天: Draw something use matrix

创建三通道二维矩阵，并绘制一个圆

#include <opencv2/opencv.hpp>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include<iostream>
#include<fstream>

using namespace cv;

int main() {
	Mat mat = Mat::zeros(100,100,CV_8UC3);
	Scalar color = Scalar(200,21,25,15);
	circle(mat, Point(50,50), 10, color,2,8,0);
	imshow("Example1",mat);
	waitKey(0);
	return 0 ;
}

Something extra

读取一个图片，返回鼠标处的RGB值:

#include<opencv2/opencv.hpp>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include<iostream>
#include<fstream>

using namespace cv;
using namespace std;

void onMouseMove(int event, int x, int y, int flags, void* src){
	if(event == EVENT_FLAG_LBUTTON){
	 Mat *img = (Mat*)src;
	 int b = img->at<Vec3b>(y,x)[0];
	 int g = img->at<Vec3b>(y,x)[1];
	 int r = img->at<Vec3b>(y,x)[2];
	 printf("Point(%d,%d): (%d,%d,%d)\n",x,y,r,g,b);
	}
}

int main(int argc, char** argv){
	if((argc!=2)){
		cerr<<"Error: Only take an argument.";
		return -1;
	}
	String picName = argv[1];
	Mat img = imread(picName);
	if(img.empty()){
	cerr<<"Error: No such file.";
		return -1;
	}

	imshow(picName,img);
	setMouseCallback(picName,onMouseMove,&img);
	waitKey(0);

	return 0;
}

An improvement ( and a bug fix) on the side

#include<opencv2/opencv.hpp>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include<iostream>
#include<fstream>
#include <windows.h>

using namespace cv;
using namespace std;
int MouseDown=0;
void onMouseMove(int event, int x, int y, int flags, void* src){
	Mat *img = (Mat*)src;
	if(x<=0 || y<=0 || x>=img->cols || y>=img->rows)
		return;
	if(event==EVENT_LBUTTONDOWN)
		MouseDown = 1;
	if(event == EVENT_LBUTTONUP)
		MouseDown = 0;

	if((event == EVENT_MOUSEMOVE && MouseDown)||MouseDown){
		int b = img->at<Vec3b>(y,x)[0];
		int g = img->at<Vec3b>(y,x)[1];
		int r = img->at<Vec3b>(y,x)[2];
		printf("Point(%d,%d): (%d,%d,%d)\n",x,y,r,g,b);
	}
}

int main(int argc, char** argv){
	if((argc!=2)){
		cerr<<"Error: Only take an argument.";
		return -1;
	}
	String picName =argv[1];
	Mat img = imread(picName);
	if(img.empty()){
	cerr<<"Error: No such file.";
		return -1;
	}
	imshow(picName,img);
	setMouseCallback(picName,onMouseMove,&img);
	waitKey(0);
	return 0;
}

Fix: Invalid coordinates crack.

Update: Press & Move to get continous values of pixels.

We may create a sketch program via this.

Another update: Change the if-condition to make single press avalible.