//Exercises at end of Chapter 5,《learning OpenCV3》
#include "stdafx.h"
#include <opencv2/opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
void help(const char **argv) {
cout << "\n\n"
<< "This program solves the Exercises at the end of Chapter 5 \n"
<< "Call:\n"
<< argv[0] << " <path/image_name>\n\n"
<< "For example: " << argv[0] << " / test.jpg\n"
<< endl;
}
int main( int argc, const char** argv )
{
help(argv);
if(argc < 2) {
cout << "\nERROR: You had too few parameters.\n" << endl;
return -1;
}
/************************************************************************/
/*5.1. Drawing practice: load or create and display a color image. Draw one example of
every shape and line that OpenCV can draw. */
/************************************************************************/
Mat src = imread("e:/template/lena.jpg");
cv::circle(src,Point(100,100),100,Scalar(255,255,255),2); //circle
cv::rectangle(src,Point(0,0),Point(300,300),Scalar(255,255,255),2);//rectangle
cv::line(src,Point(0,0),Point(300,300),Scalar(255,255,255),2);//line
cv::ellipse(src,cv::Point(100,100),Size(100,100),45,0,180,Scalar(255,0,0),2);//ellipse
/************************************************************************/
/*5.2. Grayscale: load and display a color image.
a. Turn it into three-channel grayscale (it is still an BGR image, but it looks gray
to the user).
b. Draw color text onto the image.*/
/************************************************************************/
//a
Mat tmp;
cvtColor(src,tmp,COLOR_BGR2GRAY);
cvtColor(tmp,src,COLOR_GRAY2BGR);
//b
putText(src,"puttext",Point(50,30),CV_FONT_HERSHEY_DUPLEX,1.0f,Scalar(0,255,0));
/************************************************************************/
/*5.5. Use cv::LineIterator to count pixels on different line segments in, say, a 300 × 300 image.
a. At what angles do you get the same number of pixels for 4-connected and
8-connected lines?
b. For line segment angles other than the above, which counts more pixels:
4-connected or 8-connected lines?
c. For a given line segment, explain the difference in the length of the line compared
to the number of pixels you count iterating along the line for
both 4-connected and 8-connected? Which connectedness is closer to the true
line length?
/************************************************************************/
//a、
LineIterator it_4_x(src, Point(0,0), Point(0,100), 4);
LineIterator it_8_x(src, Point(0,0), Point(0,100), 4);
LineIterator it_4_y(src, Point(0,0), Point(100,0), 4);
LineIterator it_8_y(src, Point(0,0), Point(100,0), 4);
cout << "it_4_x " <<it_4_x.count<<" it_8_x "<<it_8_x.count<<endl;
cout << "it_4_y " <<it_4_y.count<<" it_8_y "<<it_8_y.count<<endl;
//b the answer is: 4-connected counts more pixels than 8-connected counts
LineIterator it_4(src, Point(0,0), Point(100,100), 4);
LineIterator it_8(src, Point(0,0), Point(100,100), 8);
cout << "it_4 " <<it_4.count<<" large than it_8 "<<it_8.count<<endl;
//c
// the difference is the same as the difference between 4-connected and 8-connected
// I veleve the 8-connected is closer to the true line length.
waitKey();
return 0;
}