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--- opencv_tutorials_t1 [2016/06/06 14:03] – created joaomatos
+++ opencv_tutorials_t1 [2017/05/13 16:55] (current) – [Using your Webcam Image] acater
@@ Line 1: / Line 1: @@
-Tutorial 1 -
+===== Tutorial 1 =====
+ On this tutorial you will learn how to open an image , and change from RGB colored to gray scale and HSV.At the end you will learn the same thing but using the live webcam stream.
+I recommend you to type the code on your own to get familiarized with the program language. If you have trouble , the original code is attached bellow ( Running on Visual Studio 2015 + OpenCV 3.1 ) * Check the installation guide to make sure that you linked all the OpenCV modules to your Visual Studio.
+{{::basic_operations.rar|Basic operations using image}}
+{{::basic_operations_using_webcam.rar|Basic operations using webcam}}
+----
+===== Basic Operations =====
+{{ ::basic_op.jpg?direct |}}
+<Code:c++ linenums:1>
+//Blocks that we will need on this program
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/core/core.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+// declaring the namespaces
+using namespace std;
+using namespace cv;
+int main(int argc, char *argv[])
+{
+	//Declaring variables to store the colored,gray scale and HSV images
+	Mat colorimage;
+	Mat grayimage;
+	Mat hsvimage;
+	//Read the color image from your PC.
+	//Change the argument of the imread function to your image's path.
+	colorimage = imread("C:/Users/jcunhamatos/Desktop/s63.jpg");
+	//Resize function to resize your image
+	resize(colorimage, colorimage, Size(640, 480));
+	//Convert Color function.
+	//cvtColor(source image , converted image , type of conversion )
+	//You can check a list of possible convertions on the opencv website
+	// The third argument will define the conversion.
+	// COLOR TO GRAY (CV_BGR2GRAY)
+	cvtColor(colorimage, grayimage, CV_BGR2GRAY);
+	//COLOR TO HSV  ( CV_BGR2HSV)
+	cvtColor(colorimage, hsvimage, CV_BGR2HSV);
+	//Function to create windows to display your image. The type of the window
+	//can be defined on the second argument
+	//Can be omitted ( just use imshow ) if you want to use the default window properties.
+	namedWindow("Color Image", CV_WINDOW_NORMAL);
+	namedWindow("GrayScale Image", CV_WINDOW_NORMAL);
+	namedWindow("HSV Image", CV_WINDOW_NORMAL);
+	//function to show the image on the specified window (first argument)
+	imshow("Color Image", colorimage);
+	imshow("GrayScale Image", grayimage);
+	imshow("HSV image", hsvimage);
+	//Press any key to end the program
+	waitKey(0);
+	return 0;
+}
+</Code>
+----
+===== Understanding the Code =====
+<Code:c++ linenums:1>
+//Blocks that we will need on this program
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/core/core.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+// declaring the namespaces
+using namespace std;
+using namespace cv;
+</Code>
+**Line 1 to 11**:
+ First we have to include the modules from OpenCV that will be used on the program. Each modules has its own functions and Variables type. (For example: the Mat variable type , the cvtColor function , the imshow function , etc... - each one is inside of one OpenCV module , that needs to be included in order to make the program compile). The "usingnamespace" is convenient to declare always because it avoid us to type cv::OpenCVFunction  or std::StandardFunction always before using the function for the opencv scope or standard scope.
+----
+<Code:c++ linenums:13>
+int main(int argc, char *argv[])
+{
+	//Declaring variables to store the colored,gray scale and HSV images
+	Mat colorimage;
+	Mat grayimage;
+	Mat hsvimage;
+</Code>
+**Line 13 to 19**
+ To Store images we will the Mat variable type.
+----
+<Code:c++ linenums:20>
+//Read the color image from your PC.
+	//Change the argument of the imread function to your image's path.
+	colorimage = imread("C:/Users/jcunhamatos/Desktop/s63.jpg");
+	//Resize function to resize your image
+	resize(colorimage, colorimage, Size(640, 480));
+	//Convert Color function.
+	//cvtColor(source image , converted image , type of conversion )
+	//You can check a list of possible convertions on the opencv website
+	// The third argument will define the conversion.
+	// COLOR TO GRAY (CV_BGR2GRAY)
+	cvtColor(colorimage, grayimage, CV_BGR2GRAY);
+	//COLOR TO HSV  ( CV_BGR2HSV)
+	cvtColor(colorimage, hsvimage, CV_BGR2HSV);
+</Code>
+**Line 20 to 37**
+ First we have to open the image using the **"imread"** function , that takes the path of your image on your computer as argument. We can use the **"resize"** function to set the width and height of the picture (avoid to open big files) . A very useful function from OpenCV is the **"cvtColor"** , which convert the image "color type". The type of the conversion is set on the third argument - on this case , the color from the original picture is RGB , and we want to convert to gray scale (CV_BGR2GRAY) and convert to HSV (CV_BGR2HSV).
+----
+<Code:c++ linenums:38>
+//Function to create windows to display your image. The type of the window
+	//can be defined on the second argument
+	//Can be omitted ( just use imshow ) if you want to use the default window properties.
+	namedWindow("Color Image", CV_WINDOW_NORMAL);
+	namedWindow("GrayScale Image", CV_WINDOW_NORMAL);
+	namedWindow("HSV Image", CV_WINDOW_NORMAL);
+	//function to show the image on the specified window (first argument)
+	imshow("Color Image", colorimage);
+	imshow("GrayScale Image", grayimage);
+	imshow("HSV image", hsvimage);
+	//Press any key to end the program
+	waitKey(0);
+	return 0;
+}
+</Code>
+**Line 20 to 37**
+ To show the results we first open a window , using the function **"namedWindow"** , which the second argument defines the window properties ( if it can be sized , etc.. ) . Then we use the **"imshow"** function to display the Mat variable (second argument) on the specified window ( first argument ). The **"namedWindow"** function can be omitted if you want to use the default window properties (auto size).
+----
+===== Using your Webcam Image =====
+ To use the webcam live video instead of an saved image, you just need to insert a infinite do loop , and your video will be a collection of frames from your webcam. The new code will be.
+<Code:c++ linenums:1>
+//Blocks that we will need on this program
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/core/core.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+// declaring the namespaces
+using namespace std;
+using namespace cv;
+int main(int argc, char *argv[])
+{
+	//Declaring variables to store the colored,gray scale and HSV images
+	Mat colorimage;
+	Mat grayimage;
+	Mat hsvimage;
+	//Open the default camera
+	VideoCapture capture(0);
+	//Check for Failure
+	if (!capture.isOpened())
+	{
+		printf("Failed to open the webcam");
+	}
+	//Set Capture device properties.
+	capture.set(CV_CAP_PROP_FRAME_WIDTH, 640);
+	capture.set(CV_CAP_PROP_FRAME_HEIGHT, 480);
+	char key=0;
+		//Loop will stop if "q" is pressed in the keyboard
+		while (key != 'q')
+		{
+			//Capture a frame of the webcam live video and store it on the image variable
+			capture >> colorimage;
+		//Convert Color function.
+		//cvtColor(source image , converted image , type of conversion )
+		//You can check a list of possible convertions on the opencv website
+		// The third argument will define the conversion.
+		// COLOR TO GRAY (CV_BGR2GRAY)
+		cvtColor(colorimage, grayimage, CV_BGR2GRAY);
+		//COLOR TO HSV  ( CV_BGR2HSV)
+		cvtColor(colorimage, hsvimage, CV_BGR2HSV);
+		//Function to create windows to display your image. The type of the window
+		//can be defined on the second argument
+		//Can be omitted ( just use imshow ) if you want to use the default window properties.
+		namedWindow("Color Image", CV_WINDOW_NORMAL);
+		namedWindow("GrayScale Image", CV_WINDOW_NORMAL);
+		namedWindow("HSV Image", CV_WINDOW_NORMAL);
+		//function to show the image on the specified window (first argument)
+		imshow("Color Image", colorimage);
+		imshow("GrayScale Image", grayimage);
+		imshow("HSV image", hsvimage);
+		//Press q to end the program
+		key = waitKey(25);
+	}
+	return 0;
+}
+</Code>
+** What is changed ? **
+<Code:c++ linenums:20>
+//Open the default camera
+	VideoCapture capture(0);
+	//Check for Failure
+	if (!capture.isOpened())
+	{
+		printf("Failed to open the webcam");
+	}
+	//Set Capture device properties.
+	capture.set(CV_CAP_PROP_FRAME_WIDTH, 640);
+	capture.set(CV_CAP_PROP_FRAME_HEIGHT, 480);
+</Code>
+ We changed the **"imread"** for the **"VideoCapture"** which will capture from your default video source (capture(0)) and the **"resize"** for the **"capture.set"** function.
+----
+<Code:c++ linenums:34>
+char key=0;
+		//Loop will stop if "q" is pressed in the keyboard
+		while (key != 'q')
+		{
+                        //Capture a frame of the webcam live video and store it on the image variable
+			capture >> colorimage;
+</Code>
+The loop will run until the "q" key on the keyboard is pressed (we need to declare the key variable first ). The video shown on the images will be a collection of frames took from your webcam ( using the assign **capture >> colorimage**) the color image will store the webcam frame . The rest of the code is the same thing as the last code , converting to gray scale and HSV.  At the end we just need to assign the **"waitKey"** command to the key variable and close the loop.
+\\
+The video below demonstrates the program as it is run in real time.
+\\
+{{youtube>PqW0GsMVRd0?medium}}