CustomGLWidget.cpp

/*************************************************************************
   Copyright (c) 2010 Rafael Palomar
   
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY;
   without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

*************************************************************************/

/** \file CustomGLWidget.cpp
 *
 * This file contains the implementation for the CustomGLWidget class
 *
 */
#include "CustomGLWidget.h"

#include <iostream>
#include <QTimer>
#include <QMessageBox>
#include "cv.h"
#include "highgui.h"

/** \brief Constructor
 *
 * This function initializes the member variables for the CustomGLWidget class. In addition
 * the function performs the connection between signals and slots, which in this case is referred
 * to the connection between the timer signal and the capture/drawing slot.
 *
 * \arg parent parent widget.
 *
 */
CustomGLWidget::CustomGLWidget(QWidget *parent):QGLWidget(parent)
{
	//Initialize variable members
	m_timer = new QTimer();
	m_image = 0;
	m_capture = cvCaptureFromCAM(0);
	if(!m_capture)
		QMessageBox::critical(this,"Error","Error initializing capture from WebCam");

	//Get an initial frame from the webcam
	m_image = cvQueryFrame(m_capture);

	//Connect the timer signal with the capture action
	connect(m_timer, SIGNAL(timeout()), this, SLOT(captureFrame()));	
	
	//Start the timer scheduled for firing every 33ms (30fps)
	m_timer->start(33);	
}

/** \brief Destructor
 *
 * This function releases the capture from the webcam by calling
 * the proper OpenCV function.
 */
CustomGLWidget::~CustomGLWidget()
{
	//Release the capture
	cvReleaseCapture(&m_capture);		
}


/** \brief Initialize OpenGL
 *
 * This function is the responsible for setting up the dimensions of the viewport
 * and projection matrix (in this context). Initializes the viewport to the size of
 * the widget and the projection is set up to get a "world" of size 'width' x 'height' 
 *
 */
void CustomGLWidget::initializeGL()
{
	//Adjust the viewport
	glViewport(0,0,this->width(), this->height());
	
	//Adjust the projection matrix
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-this->width()/2, this->width()/2, this->height()/2, -this->height()/2, -1, 1);	
}


/** \brief Paint GL
 *
 * This function draws the scene which in this case is the capture from the webcam.
 * in order to adapt the output from the OpenCV's capture, an inversion is needed.
 *
 */
void CustomGLWidget::paintGL()
{	
	//Clear the color buffer
	glClear(GL_COLOR_BUFFER_BIT);

	//Set the raster position
	/*
	  The position seems to be the inverse because the rendering is
	  affected by the glPixelZoom call.
	 */
	glRasterPos2i(this->width()/2,-this->height()/2);
	//Inver the image (the data coming from OpenCV is inverted)
	glPixelZoom(-1.0f,-1.0f);

	//Draw image from OpenCV capture
	glDrawPixels(m_image->width, m_image->height, GL_RGB, GL_UNSIGNED_BYTE,m_image->imageData);		
}



/** \brief Capture Frame
 *
 * This function performs the capture of a frame from the webcam and
 * calls the function to render the scene.
 *
 */
void CustomGLWidget::captureFrame()
{	
	//Get an image from the webcam
	m_image = cvQueryFrame(m_capture);
	
	//Draw the scene
	glDraw();	
}