Capture RGB from Kinnect with Openni and show with OpenCV

Question

I need to capture the color RGB image from a Kinnect camera, but I want to show it in OpenCV as this is only a part of a bigger program. I know OpenCV has compatibility with OpenNI if you set the flag, but although I tried hard CMake couldn't find the path to OpenNI2 so I couldn't build OpenCV with OpenNI. Anyway I think it is good to know how to manually convert OpenNI frames to openCV frames, so I decided to follow this way.

For capturing the color frame in OpenNI I tried the following:

openni::Device device;  
openni::VideoStream  color;
openni::VideoFrameRef colorFrame;

rc = openni::OpenNI::initialize();
rc = device.open(openni::ANY_DEVICE);
rc = color.create(device, openni::SENSOR_COLOR);
rc = color.start();

color.readFrame(&colorFrame);
const openni::RGB888Pixel* imageBuffer = (const openni::RGB888Pixel*)colorFrame.getData();

But now I don't understand how to do the conversion to cv::Mat.

Does any anybody manged to do this?

Answer 1

Ok, first you should separate initialization from the loop for reading frames, this way.

Initialization

openni::Device device;  
openni::VideoStream  color;
openni::VideoFrameRef colorFrame;

rc = openni::OpenNI::initialize();
rc = device.open(openni::ANY_DEVICE);
rc = color.create(device, openni::SENSOR_COLOR);
rc = color.start();

Mat frame;

Now comes the main loop for reading frames. You have done almost everything, the only thing left is to copy the buffer to the openCV Mat.

Loop for reading frames

while (true)
{
   color.readFrame(&colorFrame);
   const openni::RGB888Pixel* imageBuffer = (const openni::RGB888Pixel*)colorFrame.getData();

   frame.create(colorFrame.getHeight(), colorFrame.getWidth(), CV_8UC3);
   memcpy( frame.data, imageBuffer, 3*colorFrame.getHeight()*colorFrame.getWidth()*sizeof(uint8_t) );

   cv::cvtColor(frame,frame,CV_BGR2RGB); //this will put colors right
}