Kinect SDK C++ - 2. Kinect Depth Data

Today we will learn how to get depth data from a kinect and what the format of the data is

kinect code

kinect Initialization

To get the depth data from the kinect, simply change the argument to NuiImageStreaOpen().

The First argument is now NUI_IMAGE_TYPE_DEPATH,telling the Kinect that wo now want depath images

instead of RGB iamges.(For clarity we also changed the name of the handle to reflect this)

We also should enable the Near Mode.let the kinect to be more sensitive to closer objects(say from 50cm to

200cm),otherwise,from 80 to 400cm.

To done that,passing flag NUI_IMAGE_FLAG_ENABLE_NEAR_MODE as the third argument

<span style="font-size:12px;"><span style="font-size:10px;">// NEW VARIABLE
HANDLE depthStream;

bool initKinect() {
// Get a working kinect sensor
int numSensors;
if (NuiGetSensorCount(&numSensors) < 0 || numSensors < 1) return false;
if (NuiCreateSensorByIndex(0, &sensor) < 0) return false;

// Initialize sensor
sensor->NuiInitialize(NUI_INITIALIZE_FLAG_USES_DEPTH | NUI_INITIALIZE_FLAG_USES_COLOR);

// --------------- START CHANGED CODE -----------------
sensor->NuiImageStreamOpen(
NUI_IMAGE_TYPE_DEPTH,                     // Depth camera or rgb camera?

NUI_IMAGE_RESOLUTION_640x480,             // Image resolution
NUI_IMAGE_STREAM_FLAG_ENABLE_NEAR_MODE,   // Image stream flags, e.g. near mode
2,      // Number of frames to buffer
NULL,   // Event handle
&depthStream);
// --------------- END CHANGED CODE -----------------
return sensor;
}</span></span>

For more information about the near mode,please prefer to offficial blog.

getting a depth frame from the kinect

the display of the dapth image from the kinect in grayscale.Each pixel will just be the pixel's distance

from the kinect(in millimeters)mod 256.

note the NuiDepthPixelToDepth fuction,calling this function returns the depth in millimeters at that pixel.

The depth data is 16 bits,so we use a USHORT to read it in.

<span style="font-size:12px;"><span style="font-size:10px;">      const USHORT* curr = (const USHORT*) LockedRect.pBits;
const USHORT* dataEnd = curr + (width*height);

while (curr < dataEnd) {
// Get depth in millimeters
USHORT depth = NuiDepthPixelToDepth(*curr++);

// Draw a grayscale image of the depth:
// B,G,R are all set to depth%256, alpha set to 1.
for (int i = 0; i < 3; ++i)
*dest++ = (BYTE) depth%256;
*dest++ = 0xff;
}
</span></span>

that's all the Kinect code! The rest is just how to get it to display.