Sample to grab depth frames from an Asus Xtion or Occipital Structure depth sensor with OpenNI2 and OpenCV3

opencvni.cpp

/*
 * Build command:
 * g++ -o opencvni opencvni.cpp `pkg-config --cflags --libs opencv`
*/

#include "opencv2/videoio/videoio.hpp"
#include "opencv2/highgui/highgui.hpp"

#include <iostream>

using namespace cv;

static void colorizeDisparity( const Mat& gray, Mat& rgb, double maxDisp=-1.f, float S=1.f, float V=1.f )
{
    CV_Assert( !gray.empty() );
    CV_Assert( gray.type() == CV_16UC1 );

    if( maxDisp <= 0 )
    {
        maxDisp = 0;
        minMaxLoc( gray, 0, &maxDisp );
    }

    rgb.create( gray.size(), CV_8UC3 );
    rgb = Scalar::all(0);
    if( maxDisp < 1 )
        return;

    for( int y = 0; y < gray.rows; y++ )
    {
        for( int x = 0; x < gray.cols; x++ )
        {
            unsigned short d = gray.at<unsigned short>(y,x);
            unsigned int H = ((unsigned short)maxDisp - d) * 240 / (unsigned short)maxDisp;

            unsigned int hi = (H/60) % 6;
            float f = H/60.f - H/60;
            float p = V * (1 - S);
            float q = V * (1 - f * S);
            float t = V * (1 - (1 - f) * S);

            Point3f res;

            if( hi == 0 ) //R = V,  G = t,  B = p
                res = Point3f( p, t, V );
            if( hi == 1 ) // R = q, G = V,  B = p
                res = Point3f( p, V, q );
            if( hi == 2 ) // R = p, G = V,  B = t
                res = Point3f( t, V, p );
            if( hi == 3 ) // R = p, G = q,  B = V
                res = Point3f( V, q, p );
            if( hi == 4 ) // R = t, G = p,  B = V
                res = Point3f( V, p, t );
            if( hi == 5 ) // R = V, G = p,  B = q
                res = Point3f( q, p, V );

            uchar b = (uchar)(std::max(0.f, std::min (res.x, 1.f)) * 255.f);
            uchar g = (uchar)(std::max(0.f, std::min (res.y, 1.f)) * 255.f);
            uchar r = (uchar)(std::max(0.f, std::min (res.z, 1.f)) * 255.f);

            rgb.at<Point3_<uchar> >(y,x) = Point3_<uchar>(b, g, r);
        }
    }
}

static float getMaxDisparity( VideoCapture& capture )
{
    const int minDistance = 400; // mm
    float b = (float)capture.get( CAP_OPENNI_DEPTH_GENERATOR_BASELINE ); // mm
    float F = (float)capture.get( CAP_OPENNI_DEPTH_GENERATOR_FOCAL_LENGTH ); // pixels
    return b * F / minDistance;
}

int main()
{
	VideoCapture capture( CAP_OPENNI2_ASUS );
	if( !capture.isOpened() )
    {
        std::cout << "***** Can not open a capture object." << std::endl;
        return -1;
    }
	for(;;)
	{
	    Mat disparityMap;
	    capture >> disparityMap;
	    Mat colorDisparityMap;
        colorizeDisparity( disparityMap, colorDisparityMap, -1 );
        Mat validColorDisparityMap;
        colorDisparityMap.copyTo( validColorDisparityMap, disparityMap != 0 );
	    imshow( "depth map", validColorDisparityMap );
	    if( waitKey( 30 ) >= 0 )
	        break;
	}
	return 0;
}