Tuesday, March 11, 2014

Video Capture using OpenCV with VC++

Video Capture using OpenCV with VC++

Introduction

It is simple video capture application using Windows form with Visual C++. This project demonstrate the Visual C++ Configuration for OpenCV as well as create windows form application.



OpenCV is the Open Computer Vision. It is open source library for image processing. This article helps programmers to configure the visual studio for visual c++ to run OpenCV application using windows controls. OpenCV library can be integrated into visual studio. It easy to configure. Following six step shows the how to configure the visual studio 2010. This article having the video capture project, which is made in Visual Studio 2010 version.

Configuration Visual C++

Video :

Part I:

Part II:

Prepare Visual Studio 2010

Step 1:

Go to Property Manager of project Select "Debug | Win32" Right click on it. then Select Properties then follow second step.


Step 2:

Select the General subcategory from C/C++ category. Select the Additional Include Directories, add following path.

C:\opencv\build\include;

For 64bit :

C:\opencv\build\x86\vc10\bin ;

For 32bit :

C:\opencv\build\x64\vc10\bin ;







Step 3:


Set the library path to "C:\opencv\build\x86\vc10\lib" if the system is 64 bit, else set library path to "C:\opencv\build\x64\vc10\lib". then click on Ok button.






Step 4:


In this step, Need to add the OpenCV library. These are located at "C:\opencv\build\x86\vc10\lib" path location.



For Debug


opencv_calib3d248d.libopencv_contrib248d.libopencv_core248d.lib
opencv_features2d248d.libopencv_flann248d.libopencv_gpu248d.lib
opencv_highgui248d.libopencv_imgproc248d.libopencv_legacy248d.lib
opencv_ml248d.libopencv_nonfree248d.libopencv_objdetect248d.lib
opencv_ocl248d.libopencv_photo248d.libopencv_stitching248d.lib
opencv_superres248d.libopencv_video248d.libopencv_videostab248d.lib







For Release

Remove the last 'd' from file name. e.g. opencv_calib3d248d.lib to opencv_calib3d248.lib


Step 5:

Change Common Language Runtime Support, Pure MSIL Common Language RunTime Support (/clr:pure) to Common Language RunTime Support (/clr). then click on "Ok" to finish configuration.


Step 6:

Add following Environmental Path.
For 64bit : C:\opencv\build\x86\vc10\bin ;
For 32bit : C:\opencv\build\x64\vc10\bin ;

Using the code

Before going to write the code, need to include the header files as listed follow. capture and frame variable declared outside the namespace follow by the header files. These variable are the pointer variables.
#pragma once
#include "opencv/cv.h"
#include "opencv/highgui.h"
#include "opencv2/opencv.hpp"
#include "opencv2/core/core.hpp"

CvCapture* capture;
IplImage* frame;  





cvCaptureFromCAM function initialized the capture with first camera (index 0). If index passed as 1 then, it initialized with second camera and so on.


capture = cvCaptureFromCAM(0); 



Track bar initialized with total number of video frames. CV_CAP_PROP_FRAME_COUNT is a constant which passed to cvGetCaptureProperty to get total number of frames works with video file, not for cameras.


trackBar1->Maximum = (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_COUNT); 



Releases the capture from resources.


cvReleaseCapture(&capture);  

Following function capture the video from camera and also from video file like *.avi, *.mp4 .
private: System::Void button2_Click(System::Object^  sender, System::EventArgs^  e) 
{
   if(comboBox1->Text == "")
   {
    MessageBox::Show(this,"Select Capture Method","Error!!!");
   }
   if(button2->Text == "Start")
   {
    if (comboBox1->Text == "Capture From Camera")
    {                    
        capture = cvCaptureFromCAM(0);
        trackBar1->Minimum = 0;
        trackBar1->Maximum = 0;
        button2->Text = "Stop";
        timer1->Start();
    }
    else if (comboBox1->Text == "Capture From File")
    {    
        openFileDialog1->Filter = "AVI files (*.avi)|*.txt|All files (*.*)|*.*";
        openFileDialog1->FilterIndex = 2;
        openFileDialog1->RestoreDirectory = true;
        openFileDialog1->FileName ="";
        if ( openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK )
        {        
         char *fileName = (char*) Marshal::StringToHGlobalAnsi(openFileDialog1->FileName).ToPointer();                    
         capture = cvCaptureFromFile(fileName);
         trackBar1->Minimum = 0;
         trackBar1->Maximum = (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_COUNT);
         button2->Text = "Stop";
         timer1->Start();
       }                
    }
   }
   else if(button2->Text == "Stop")
   {
     cvReleaseCapture(&capture);        
     button2->Text = "Start";
     timer1->Stop();
   }
}   

cvQueryFrame function query the frame current video capture. and assigned to frame variable.
frame = cvQueryFrame(capture); 

Following statement is the replacement for the imshow( "windowname" , frame ) function of OpenCV which shows the image frame.
pictureBox1->Image  = gcnew System::Drawing::Bitmap(frame->width,frame->height,frame->widthStep,System::Drawing::Imaging::PixelFormat::Format24bppRgb,(System::IntPtr) frame->imageData);
pictureBox1->Refresh(); 

Timer initialized with 30 intervals. It executes the function after 30 interval of time. Following function Query the frame , and extract the video properties. Following constants are used to extract video properties
CV_CAP_PROP_POS_FRAMES : Get current position of video frame.
CV_CAP_PROP_FOURCC : Get video codec information.
CV_CAP_PROP_POS_MSEC : Get Time information.
CV_CAP_PROP_FRAME_HEIGHT : Get video frame height.
CV_CAP_PROP_FRAME_WIDTH : Get video frame width.
CV_CAP_PROP_FPS : Get video frame rate (Fame Per Seconds) .
private: System::Void timer1_Tick(System::Object^  sender, System::EventArgs^  e) 
{
    try
    {        
        frame = cvQueryFrame(capture);    
        if(frame != NULL)
        {
            pictureBox1->Image  = gcnew System::Drawing::Bitmap(frame->width,frame->height,frame->widthStep,System::Drawing::Imaging::PixelFormat::Format24bppRgb,(System::IntPtr) frame->imageData);
            pictureBox1->Refresh();
    
            trackBar1->Value = (int)cvGetCaptureProperty(capture,CV_CAP_PROP_POS_FRAMES);            
            double codec_double = cvGetCaptureProperty(capture,CV_CAP_PROP_FOURCC);
            label6->Text = "Codec: " + System::Text::Encoding::UTF8->GetString(BitConverter::GetBytes((int)codec_double));
            label7->Text = "Time: " + (TimeSpan::FromMilliseconds( cvGetCaptureProperty(capture,CV_CAP_PROP_POS_MSEC) ).ToString())->Substring(0, 8);
            label8->Text = "Frame No.: " + (int)cvGetCaptureProperty(capture,CV_CAP_PROP_POS_FRAMES);
            label9->Text = "Video Resolution: " + (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_HEIGHT) + " X " + (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_WIDTH);
            label11->Text = "Video Frame Rate: " + (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FPS);
        }
    }catch(...){}
} 

Track Bar initialized with position of current video frame. CV_CAP_PROP_POS_FRAMES is a constant which is used for getting the current position of video frame.
private: System::Void trackBar1_Scroll(System::Object^  sender, System::EventArgs^  e) 
{
    cvSetCaptureProperty(capture,CV_CAP_PROP_POS_FRAMES, trackBar1->Value);
}  

Points of Interest

  • Learn how to configure visual c++.
  • Learn how to capture the video from video file as well as cameras.
  • Learn how to extract the video properties.

References

[1] http://opencv.org/
[2] http://en.wikipedia.org/wiki/OpenCV
[3] http://docs.opencv.org/
[4] http://www.cs.iit.edu/~agam/cs512/lect-notes/opencv-intro/opencv-intro.html