OPENNI学习实践-openni+kinect 获取真实世界坐标

#include <stdlib.h>
#include <iostream>
#include <string>

#include <XnCppWrapper.h>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/core/core.hpp>

using namespace std;
using namespace xn;
using namespace cv;

void CheckOpenNIError(XnStatus eResult,string sStatus)
{
if(eResult != XN_STATUS_OK)
cout << sStatus << "Error: " << xnGetStatusString(eResult) << endl;//P53
}

int main()
{
XnStatus eResult = XN_STATUS_OK;
DepthMetaData depthMD;
IRMetaData irData;
namedWindow("Depth Image");
namedWindow("IRImage");

Context mContext;
eResult = mContext.Init();
CheckOpenNIError(eResult,"Initialize context");

DepthGenerator mDepthGenerator;
eResult = mDepthGenerator.Create(mContext);
CheckOpenNIError(eResult,"Create depth generator");

IRGenerator mIRGenerator;
eResult = mIRGenerator.Create(mContext);
CheckOpenNIError(eResult,"Create depth generator");

mDepthGenerator.GetMirrorCap().SetMirror(true);
mIRGenerator.GetMirrorCap().SetMirror(true);

XnMapOutputMode mapMode;
mapMode.nXRes = 640;
mapMode.nYRes = 480;
mapMode.nXRes = 30;
eResult = mDepthGenerator.SetMapOutputMode(mapMode);

XnMapOutputMode MyMapMode;
MyMapMode.nXRes = 640;
MyMapMode.nYRes = 480;
MyMapMode.nFPS = 30;
mIRGenerator.SetMapOutputMode( MyMapMode );

eResult = mContext.StartGeneratingAll();

int flag=0;

while(true)
{
eResult = mContext.WaitAnyUpdateAll();
if(eResult == XN_STATUS_OK)
{

mDepthGenerator.GetMetaData(depthMD);
Mat cvDepthImage16UC1(depthMD.FullYRes(),depthMD.FullXRes(),CV_16UC1,(char*) depthMD.Data());
Mat cvDepthImage8UC1;
cvDepthImage16UC1.convertTo(cvDepthImage8UC1,CV_8UC1,255.0/(depthMD.ZRes()));
imshow("Depth Image",cvDepthImage8UC1);

mIRGenerator.GetMetaData(irData);
Mat irImage16UC1(irData.FullYRes(),irData.FullXRes(),CV_16UC1,(char*) irData.Data());
Mat irImage8UC1;
irImage16UC1.convertTo(irImage8UC1,CV_8UC1,255.0/255);
cv::circle(irImage8UC1,Point2d(MyMapMode.nXRes/2,MyMapMode.nYRes/2),10,Scalar(255),5);

XnPoint3D *ProjectivePoint=new XnPoint3D[1];
XnPoint3D *ProjectivePoint2=new XnPoint3D[1];
XnPoint3D *RealPoint=new XnPoint3D[1];
ProjectivePoint[0]=xnCreatePoint3D(MyMapMode.nXRes/2,MyMapMode.nYRes/2,depthMD(MyMapMode.nXRes/2,MyMapMode.nYRes/2));
mDepthGenerator.ConvertProjectiveToRealWorld(1,ProjectivePoint,RealPoint);
printf("z=%f",RealPoint[0].Z);

imshow("IRImage",irImage8UC1);

waitKey(30);
}
}

mContext.StopGeneratingAll();
mContext.Shutdown();
return 0;
}

重点在于

XnPoint3D *ProjectivePoint=new XnPoint3D[1];
XnPoint3D *ProjectivePoint2=new XnPoint3D[1];
XnPoint3D *RealPoint=new XnPoint3D[1];
ProjectivePoint[0]=xnCreatePoint3D(MyMapMode.nXRes/2,MyMapMode.nYRes/2,depthMD(MyMapMode.nXRes/2,MyMapMode.nYRes/2));
mDepthGenerator.ConvertProjectiveToRealWorld(1,ProjectivePoint,RealPoint);

首先定义几个点，然后选取需要转换的点在深度图中的位置，然后利用函数进行计算即可得到真实坐标值。
利用DepthGenerator 中GetDepthMap或者getMetaData均可获得深度图像的像素值；GetMetaData函数是将像素值填充到DepthMetaData的对象中，GetDepthMap是直接读取像素值。

XnPoint3D是保持类型为float的x、y、z的结构，为将像素值转为点云，须利用DepthGenerator的ConvertProjectToRealWorld函数：

01.XnStatus  ConvertProjectiveToRealWorld (XnUInt32 nCount, const XnPoint3D aProjective[], XnPoint3D aRealWorld[]) const

其中nCount表示点数数目，aProjective表示投影坐标下所有(x,y,z)的值，aRealWorld表示实际空间坐标值，该坐标系的坐标原点是：depth map的中心投影到Kinect所在平面上的点。