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134 lines
6.6 KiB
ReStructuredText
134 lines
6.6 KiB
ReStructuredText
*******
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HighGUI
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*******
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.. highlight:: cpp
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Using Kinect and other OpenNI compatible depth sensors
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======================================================
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Depth sensors compatible with OpenNI (Kinect, XtionPRO, ...) are supported through ``VideoCapture`` class. Depth map, RGB image and some other formats of output can be retrieved by using familiar interface of ``VideoCapture``.
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In order to use depth sensor with OpenCV you should do the following preliminary steps:
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#.
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Install OpenNI library (from here http://www.openni.org/downloadfiles) and PrimeSensor Module for OpenNI (from here https://github.com/avin2/SensorKinect). The installation should be done to default folders listed in the instructions of these products, e.g.:
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.. code-block:: text
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OpenNI:
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Linux & MacOSX:
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Libs into: /usr/lib
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Includes into: /usr/include/ni
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Windows:
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Libs into: c:/Program Files/OpenNI/Lib
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Includes into: c:/Program Files/OpenNI/Include
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PrimeSensor Module:
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Linux & MacOSX:
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Bins into: /usr/bin
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Windows:
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Bins into: c:/Program Files/Prime Sense/Sensor/Bin
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If one or both products were installed to the other folders, the user should change corresponding CMake variables ``OPENNI_LIB_DIR``, ``OPENNI_INCLUDE_DIR`` or/and ``OPENNI_PRIME_SENSOR_MODULE_BIN_DIR``.
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#.
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Configure OpenCV with OpenNI support by setting ``WITH_OPENNI`` flag in CMake. If OpenNI is found in install folders OpenCV will be built with OpenNI library (see a status ``OpenNI`` in CMake log) whereas PrimeSensor Modules can not be found (see a status ``OpenNI PrimeSensor Modules`` in CMake log). Without PrimeSensor module OpenCV will be successfully compiled with OpenNI library, but ``VideoCapture`` object will not grab data from Kinect sensor.
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#.
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Build OpenCV.
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VideoCapture can retrieve the following data:
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#.
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data given from depth generator:
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* ``CV_CAP_OPENNI_DEPTH_MAP`` - depth values in mm (CV_16UC1)
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* ``CV_CAP_OPENNI_POINT_CLOUD_MAP`` - XYZ in meters (CV_32FC3)
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* ``CV_CAP_OPENNI_DISPARITY_MAP`` - disparity in pixels (CV_8UC1)
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* ``CV_CAP_OPENNI_DISPARITY_MAP_32F`` - disparity in pixels (CV_32FC1)
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* ``CV_CAP_OPENNI_VALID_DEPTH_MASK`` - mask of valid pixels (not ocluded, not shaded etc.) (CV_8UC1)
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#.
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data given from RGB image generator:
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* ``CV_CAP_OPENNI_BGR_IMAGE`` - color image (CV_8UC3)
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* ``CV_CAP_OPENNI_GRAY_IMAGE`` - gray image (CV_8UC1)
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In order to get depth map from depth sensor use ``VideoCapture::operator >>``, e. g. ::
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VideoCapture capture( CV_CAP_OPENNI );
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for(;;)
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{
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Mat depthMap;
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capture >> depthMap;
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if( waitKey( 30 ) >= 0 )
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break;
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}
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For getting several data maps use ``VideoCapture::grab`` and ``VideoCapture::retrieve``, e.g. ::
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VideoCapture capture(0); // or CV_CAP_OPENNI
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for(;;)
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{
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Mat depthMap;
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Mat bgrImage;
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capture.grab();
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capture.retrieve( depthMap, CV_CAP_OPENNI_DEPTH_MAP );
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capture.retrieve( bgrImage, CV_CAP_OPENNI_BGR_IMAGE );
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if( waitKey( 30 ) >= 0 )
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break;
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}
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For setting and getting some property of sensor` data generators use ``VideoCapture::set`` and ``VideoCapture::get`` methods respectively, e.g. ::
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VideoCapture capture( CV_CAP_OPENNI );
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capture.set( CV_CAP_OPENNI_IMAGE_GENERATOR_OUTPUT_MODE, CV_CAP_OPENNI_VGA_30HZ );
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cout << "FPS " << capture.get( CV_CAP_OPENNI_IMAGE_GENERATOR+CV_CAP_PROP_FPS ) << endl;
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Since two types of sensor's data generators are supported (image generator and depth generator), there are two flags that should be used to set/get property of the needed generator:
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* CV_CAP_OPENNI_IMAGE_GENERATOR -- A flag for access to the image generator properties.
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* CV_CAP_OPENNI_DEPTH_GENERATOR -- A flag for access to the depth generator properties. This flag value is assumed by default if neither of the two possible values of the property is not set.
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Some depth sensors (for example XtionPRO) do not have image generator. In order to check it you can get ``CV_CAP_OPENNI_IMAGE_GENERATOR_PRESENT`` property.
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::
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bool isImageGeneratorPresent = capture.get( CV_CAP_PROP_OPENNI_IMAGE_GENERATOR_PRESENT ) != 0; // or == 1
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Flags specifing the needed generator type must be used in combination with particular generator property. The following properties of cameras available through OpenNI interfaces are supported:
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*
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For image generator:
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- ``CV_CAP_PROP_OPENNI_OUTPUT_MODE`` -- Three output modes are supported: ``CV_CAP_OPENNI_VGA_30HZ`` used by default (image generator returns images in VGA resolution with 30 FPS), ``CV_CAP_OPENNI_SXGA_15HZ`` (image generator returns images in SXGA resolution with 15 FPS) and ``CV_CAP_OPENNI_SXGA_30HZ`` (image generator returns images in SXGA resolution with 30 FPS, the mode is supported by XtionPRO Live); depth generator's maps are always in VGA resolution.
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*
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For depth generator:
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- ``CV_CAP_PROP_OPENNI_REGISTRATION`` -- Flag that registers the remapping depth map to image map by changing depth generator's view point (if the flag is ``"on"``) or sets this view point to its normal one (if the flag is ``"off"``). The registration process’s resulting images are pixel-aligned,which means that every pixel in the image is aligned to a pixel in the depth image.
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Next properties are available for getting only:
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- ``CV_CAP_PROP_OPENNI_FRAME_MAX_DEPTH`` -- A maximum supported depth of Kinect in mm.
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- ``CV_CAP_PROP_OPENNI_BASELINE`` -- Baseline value in mm.
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- ``CV_CAP_PROP_OPENNI_FOCAL_LENGTH`` -- A focal length in pixels.
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- ``CV_CAP_PROP_FRAME_WIDTH`` -- Frame width in pixels.
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- ``CV_CAP_PROP_FRAME_HEIGHT`` -- Frame height in pixels.
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- ``CV_CAP_PROP_FPS`` -- Frame rate in FPS.
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*
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Some typical flags combinations "generator type + property" are defined as single flags:
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- ``CV_CAP_OPENNI_IMAGE_GENERATOR_OUTPUT_MODE = CV_CAP_OPENNI_IMAGE_GENERATOR + CV_CAP_PROP_OPENNI_OUTPUT_MODE``
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- ``CV_CAP_OPENNI_DEPTH_GENERATOR_BASELINE = CV_CAP_OPENNI_DEPTH_GENERATOR + CV_CAP_PROP_OPENNI_BASELINE``
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- ``CV_CAP_OPENNI_DEPTH_GENERATOR_FOCAL_LENGTH = CV_CAP_OPENNI_DEPTH_GENERATOR + CV_CAP_PROP_OPENNI_FOCAL_LENGTH``
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- ``CV_CAP_OPENNI_DEPTH_GENERATOR_REGISTRATION = CV_CAP_OPENNI_DEPTH_GENERATOR + CV_CAP_PROP_OPENNI_REGISTRATION``
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For more information please refer to the example of usage openni_capture.cpp_ in ``opencv/samples/cpp`` folder.
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.. _openni_capture.cpp: http://code.opencv.org/projects/opencv/repository/revisions/master/raw/samples/cpp/openni_capture.cpp
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