Surf Detector

	#include <iostream>
	#include <stdio.h>
	#include <stdlib.h>
	#include "opencv2/highgui/highgui.hpp"
	#include "opencv2/imgproc/imgproc.hpp"
	#include "opencv2/core/core.hpp"
	#include "opencv2/features2d/features2d.hpp"
	using namespace std;
	using namespace cv;
	//#include "Functions.h"
	char* source_window = "Source image";
	char* corners_window = "Corners detected";
	int main()
	{
	Mat src;
	src = imread("building.jpg",CV_LOAD_IMAGE_GRAYSCALE);
	if(src.empty())
	{
	cout << "Could not open or find the image" << std::endl ;
	return -1;
	}
	// -- step 1: Detect the keypoints using SURF Detector
	int minHessian = 200;
	SurfFeatureDetector detector(minHessian);
	vector<KeyPoint> keypoints;
	detector.detect(src,keypoints);
	Mat img_keypoints;
	drawKeypoints(src,keypoints,img_keypoints,Scalar::all(-1), DrawMatchesFlags::DEFAULT);
	imshow("Keypoins", img_keypoints);
	waitKey(0);
	return 0;
	}

view raw gistfile1.cpp hosted with ❤ by GitHub

OpenCV Sobel edge detector

http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/sobel_derivatives/sobel_derivatives.html

Orignal

Sobel X Gradient

Sobel Y Gradient

Sobel Gradient

	#include <iostream>
	#include <stdio.h>
	#include <stdlib.h>
	#include "opencv2/highgui/highgui.hpp"
	#include "opencv2/imgproc/imgproc.hpp"
	#include "opencv2/core/core.hpp"
	using namespace std;
	using namespace cv;
	#include "Functions.h"
	int main()
	{
	Mat image;
	//image = imread("lena.jpg",1);
	image = imread("building.jpg",1);
	if(image.empty())
	{
	cout << "Could not open or find the image" << std::endl ;
	return -1;
	}
	/// Convert it to gray
	cvtColor( image, image, CV_RGB2GRAY );
	resize(image,image,Size(0,0),0.5,0.5,INTER_LINEAR);
	namedWindow("Image", CV_WINDOW_AUTOSIZE );
	imshow("Image", image);
	/// Generate grad_x and grad_y
	Mat grad_x, grad_y;
	Mat abs_grad_x, abs_grad_y;
	int scale = 1;
	int delta = 0;
	int ddepth = CV_16S;
	Mat grad;
	/// Gradient X
	//Scharr( image, grad_x, ddepth, 1, 0, scale, delta, BORDER_DEFAULT );
	Sobel( image, grad_x, ddepth, 1, 0, 3, scale, delta, BORDER_DEFAULT );
	convertScaleAbs( grad_x, abs_grad_x );
	/// Gradient Y
	// Scharr( image, grad_y, ddepth, 0, 1, scale, delta, BORDER_DEFAULT );
	Sobel( image, grad_y, ddepth, 0, 1, 3, scale, delta, BORDER_DEFAULT );
	convertScaleAbs( grad_y, abs_grad_y );
	/// Total Gradient (approximate)
	addWeighted( abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad );
	namedWindow("ImageSobel", CV_WINDOW_AUTOSIZE );
	imshow( "ImageSobel", grad );
	namedWindow("ImageSobelGx", CV_WINDOW_AUTOSIZE );
	imshow( "ImageSobelGx", abs_grad_x );
	namedWindow("ImageSobelGy", CV_WINDOW_AUTOSIZE );
	imshow( "ImageSobelGy", abs_grad_y );
	waitKey(0);
	return 0;
	}

view raw gistfile1.cpp hosted with ❤ by GitHub

OpenCV Tutorial 1: Mat - The basic Image Container

Color Space In OpenCV

There are, however, many other color systems each with their own advantages:

• RGB is the most common as our eyes use something similar, our display systems also compose colors using these.
• The HSV and HLS decompose colors into their hue, saturation and value/luminance components, which is a more natural way for us to describe colors. You might, for example, dismiss the last component, making your algorithm less sensible to the light conditions of the input image.
• YCrCb is used by the popular JPEG image format.
• CIE L*a*b* is a perceptually uniform color space, which comes handy if you need to measure the distance of a given color to another color.

Sample Code

	// create by using the constructor
	Mat M(2,2, CV_8UC3, Scalar(0,0,255));
	cout << "M = " << endl << " " << M << endl << endl;
	// create by using the create function()
	M.create(4,4, CV_8UC(2));
	cout << "M = "<< endl << " " << M << endl << endl;
	// create multidimensional matrices
	int sz[3] = {2,2,2};
	Mat L(3,sz, CV_8UC(1), Scalar::all(0));
	// Cannot print via operator <<
	// Create using MATLAB style eye, ones or zero matrix
	Mat E = Mat::eye(4, 4, CV_64F);
	cout << "E = " << endl << " " << E << endl << endl;
	Mat O = Mat::ones(2, 2, CV_32F);
	cout << "O = " << endl << " " << O << endl << endl;
	Mat Z = Mat::zeros(3,3, CV_8UC1);
	cout << "Z = " << endl << " " << Z << endl << endl;
	// create a 3x3 double-precision identity matrix
	Mat C = (Mat_<double>(3,3) << 0, -1, 0, -1, 5, -1, 0, -1, 0);
	cout << "C = " << endl << " " << C << endl << endl;
	Mat RowClone = C.row(1).clone();
	cout << "RowClone = " << endl << " " << RowClone << endl << endl;
	// Fill a matrix with random values
	Mat R = Mat(3, 2, CV_8UC3);
	randu(R, Scalar::all(0), Scalar::all(255));
	// Demonstrate the output formating options
	cout << "R (default) = " << endl << R << endl << endl;
	cout << "R (python) = " << endl << format(R,"python") << endl << endl;
	cout << "R (numpy) = " << endl << format(R,"numpy" ) << endl << endl;
	cout << "R (csv) = " << endl << format(R,"csv" ) << endl << endl;
	cout << "R (c) = " << endl << format(R,"C" ) << endl << endl;
	Point2f P(5, 1);
	cout << "Point (2D) = " << P << endl << endl;
	Point3f P3f(2, 6, 7);
	cout << "Point (3D) = " << P3f << endl << endl;
	vector<float> v;
	v.push_back( (float)CV_PI); v.push_back(2); v.push_back(3.01f);
	cout << "Vector of floats via Mat = " << Mat(v) << endl << endl;
	vector<Point2f> vPoints(20);
	for (size_t E = 0; E < vPoints.size(); ++E)
	vPoints[E] = Point2f((float)(E * 5), (float)(E % 7));
	cout << "A vector of 2D Points = " << vPoints << endl << endl;

view raw gistfile1.cpp hosted with ❤ by GitHub

Camera Calibration tool box from Caltech

http://www.vision.caltech.edu/bouguetj/calib_doc/
This is a release of a Camera Calibration Toolbox for Matlab^® with a complete documentation. This document may also be used as a tutorial on camera calibration since it includes general information about calibration, references and related links. 

Read Camera Write Video

	// ReadCameraWriteVideo.cpp : Defines the entry point for the console application.
	//
	#include "stdafx.h"
	#include <iostream>
	// Include standard OpenCV headers
	#include "cv.h"
	#include "highgui.h"
	using namespace std;
	// All the new API is put into "cv" namespace
	using namespace cv;
	int main (int argc, char *argv[])
	{
	// Open the default camera
	VideoCapture capture(0);
	// Check if the camera was opened
	if(!capture.isOpened())
	{
	cerr << "Could not create capture";
	return -1;
	}
	// Get the properties from the camera
	double width = capture.get(CV_CAP_PROP_FRAME_WIDTH);
	double height = capture.get(CV_CAP_PROP_FRAME_HEIGHT);
	cout << "Camera properties\n";
	cout << "width = " << width << endl <<"height = "<< height << endl;
	// Create a matrix to keep the retrieved frame
	Mat frame;
	// Create a window to show the image
	namedWindow ("Capture", CV_WINDOW_AUTOSIZE);
	// Create the video writer
	VideoWriter video("capture.avi",-1, 30, cvSize((int)width,(int)height) );
	// Check if the video was opened
	if(!video.isOpened())
	{
	cerr << "Could not create video.";
	return -1;
	}
	cout << "Press Esc to stop recording." << endl;
	// Get the next frame until the user presses the escape key
	while(true)
	{
	// Get frame from capture
	capture >> frame;
	// Check if the frame was retrieved
	if(!frame.data)
	{
	cerr << "Could not retrieve frame.";
	return -1;
	}
	// Save frame to video
	video << frame;
	// Show image
	imshow("Capture", frame);
	// Exit with escape key
	if(waitKey(1) == 27)
	break;
	}
	// Exit
	return 0;
	}

view raw gistfile1.cpp hosted with ❤ by GitHub

overloading constructors

	#include <iostream>
	using namespace std;
	class CRectangle {
	int x, y;
	public:
	CRectangle();
	CRectangle(int _x, int _y);
	void set_values (int,int);
	int area () {return (x*y);}
	};
	void CRectangle::set_values (int a, int b) {
	x = a;
	y = b;
	}
	CRectangle::CRectangle():x(0),y(0)
	{}
	CRectangle::CRectangle(int _x, int _y):x(_x),y(_y)
	{}
	int main () {
	CRectangle rect, rectb, rectc(3,4);
	rectb.set_values (5,6);
	cout << "rect area: " << rect.area() << endl;
	cout << "rectb area: " << rectb.area() << endl;
	cout << "rectc area: " << rectc.area() << endl;
	return 0;
	}

view raw gistfile1.cpp hosted with ❤ by GitHub

Output:

rect area: 0 rectb area: 30 rectc area: 12

Push structure into vector in C++

Push structure into vector in C++

	#include "stdafx.h"
	#include <stdio.h>
	#include<iostream>
	#include<vector>
	using namespace std;
	//define struct
	struct test{
	double r;
	double theta;
	};
	int _tmain(int argc, _TCHAR* argv[])
	{
	test testStr[9];
	for (int i =0;i<9;i++)
	{
	testStr[i].r = 0;
	testStr[i].theta = 0;
	}
	vector<test> strVect; // define a vector of struct
	strVect.push_back(testStr[0]);
	strVect.push_back(testStr[1]);
	printf("test structure %d\n", strVect[0].r);
	getchar();
	}

view raw gistfile1.cpp hosted with ❤ by GitHub

Latex array stretch

Stretch the row size of a table

\renewcommand\arraystretch{MyValue}% (MyValue=1.0 is for standard spacing)