libCinder demo showing openCV contour detection

CvBlobsApp.cpp

#include "cinder/app/AppBasic.h"
#include "cinder/gl/gl.h"
#include "cinder/params/Params.h"
#include "cinder/ImageIo.h"
#include "cinder/Utilities.h"

#include "cinder/Capture.h"
#include "cinder/gl/Texture.h"

#include "CinderOpenCV.h"

using namespace ci;
using namespace ci::app;
using namespace std;

class CvBlobsApp : public AppBasic {
public:
	void prepareSettings(Settings *settings);
	void setup();
	void keyDown( KeyEvent event );
	void update();
	void draw();
	
private:
	params::InterfaceGl mParams;
    
    Capture			mCap;
    gl::Texture		mTexture;
    
    typedef vector< vector<cv::Point> > ContourVector;
    ContourVector mContours;
    int mStepSize;
    int mBlurAmount;
};

void CvBlobsApp::prepareSettings(Settings *settings)
{
	settings->setWindowSize( 1024, 768 );
}

void CvBlobsApp::setup()
{
	mParams = params::InterfaceGl( "Settings", Vec2i( 200, 100 ) );
    mParams.addParam( "Threshold Step Size", &mStepSize, "min=1 max=255" );
    mParams.addParam( "CV Blur amount", &mBlurAmount, "min=3 max=55" );
    mStepSize = 10;
    mBlurAmount = 5;
	
    try {
		mCap = Capture( 640, 480 );
		mCap.start();
	}
	catch( ... ) {
		console() << "Failed to initialize capture" << std::endl;
	}
}

void CvBlobsApp::keyDown( KeyEvent event )
{
	switch( event.getChar() ){
		case 'f':
			setFullScreen( !isFullScreen() );
			break;
		default:
		break;
	}
}

void CvBlobsApp::update()
{
    if( mCap && mCap.checkNewFrame() ) {
		cv::Mat input( toOcv( mCap.getSurface() ) );
        cv::Mat gray;
        cv::Mat thresh;
        
        cv::cvtColor( input, gray, CV_RGB2GRAY );
        cv::blur( gray, gray, cv::Size( mBlurAmount, mBlurAmount ) );
        mContours.clear();
        
        for( int t = 0; t <= 255; t += mStepSize )
        {
            ContourVector vec;
            cv::threshold( gray, thresh, t, 255, CV_8U );
            cv::findContours( thresh, vec, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE );
            // put into mContours
            mContours.insert( mContours.end(), vec.begin(), vec.end() );
        }
        
        
		mTexture = gl::Texture( fromOcv( gray ) );
	}
}

void CvBlobsApp::draw()
{
	gl::clear( Color::black() ); 
    
    gl::pushMatrices();
    gl::translate( Vec2f( getWindowWidth() - 640, getWindowHeight() - 480 ) * 0.5f );
	
	if( mTexture )
    {
        gl::color( Color::white() );
		gl::draw( mTexture );
    }
    
    // draw the contours
    for( ContourVector::iterator iter = mContours.begin(); iter != mContours.end(); ++iter )
    {
        glBegin( GL_LINE_LOOP );
        
        for( vector<cv::Point>::iterator pt = iter->begin(); pt != iter->end(); ++pt )
        {
            gl::color( Color( 1.0f, 0.0f, 0.0f ) );
            gl::vertex( fromOcv( *pt ) );
        }
        
        glEnd();
    }
    
    gl::popMatrices();
    
	// draw interface
	params::InterfaceGl::draw();
}


CINDER_APP_BASIC( CvBlobsApp, RendererGl )

Note that getUniquePath() is a function in my fork of Cinder, and is not (yet?) standard. Removed from the sample.