opencv/modules/ocl/doc/camera_calibration_and_3D_reconstruction.rst
2013-11-05 23:53:51 +04:00

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Camera Calibration and 3D Reconstruction
========================================
.. highlight:: cpp
ocl::StereoBM_OCL
---------------------
.. ocv:class:: ocl::StereoBM_OCL
Class computing stereo correspondence (disparity map) using the block matching algorithm. ::
class CV_EXPORTS StereoBM_OCL
{
public:
enum { BASIC_PRESET = 0, PREFILTER_XSOBEL = 1 };
enum { DEFAULT_NDISP = 64, DEFAULT_WINSZ = 19 };
//! the default constructor
StereoBM_OCL();
//! the full constructor taking the camera-specific preset, number of disparities and the SAD window size. ndisparities must be multiple of 8.
StereoBM_OCL(int preset, int ndisparities = DEFAULT_NDISP, int winSize = DEFAULT_WINSZ);
//! the stereo correspondence operator. Finds the disparity for the specified rectified stereo pair
//! Output disparity has CV_8U type.
void operator() ( const oclMat &left, const oclMat &right, oclMat &disparity);
//! Some heuristics that tries to estmate
// if current GPU will be faster then CPU in this algorithm.
// It queries current active device.
static bool checkIfGpuCallReasonable();
int preset;
int ndisp;
int winSize;
// If avergeTexThreshold == 0 => post procesing is disabled
// If avergeTexThreshold != 0 then disparity is set 0 in each point (x,y) where for left image
// SumOfHorizontalGradiensInWindow(x, y, winSize) < (winSize * winSize) * avergeTexThreshold
// i.e. input left image is low textured.
float avergeTexThreshold;
private:
/* hidden */
};
The class also performs pre- and post-filtering steps: Sobel pre-filtering (if ``PREFILTER_XSOBEL`` flag is set) and low textureness filtering (if ``averageTexThreshols > 0`` ). If ``avergeTexThreshold = 0`` , low textureness filtering is disabled. Otherwise, the disparity is set to 0 in each point ``(x, y)`` , where for the left image
.. math::
\sum HorizontalGradiensInWindow(x, y, winSize) < (winSize \cdot winSize) \cdot avergeTexThreshold
This means that the input left image is low textured.
ocl::StereoBM_OCL::StereoBM_OCL
-----------------------------------
Enables :ocv:class:`ocl::StereoBM_OCL` constructors.
.. ocv:function:: ocl::StereoBM_OCL::StereoBM_OCL()
.. ocv:function:: ocl::StereoBM_OCL::StereoBM_OCL(int preset, int ndisparities = DEFAULT_NDISP, int winSize = DEFAULT_WINSZ)
:param preset: Parameter presetting:
* **BASIC_PRESET** Basic mode without pre-processing.
* **PREFILTER_XSOBEL** Sobel pre-filtering mode.
:param ndisparities: Number of disparities. It must be a multiple of 8 and less or equal to 256.
:param winSize: Block size.
ocl::StereoBM_OCL::operator ()
----------------------------------
Enables the stereo correspondence operator that finds the disparity for the specified rectified stereo pair.
.. ocv:function:: void ocl::StereoBM_OCL::operator ()(const oclMat& left, const oclMat& right, oclMat& disparity)
:param left: Left image. Only ``CV_8UC1`` type is supported.
:param right: Right image with the same size and the same type as the left one.
:param disparity: Output disparity map. It is a ``CV_8UC1`` image with the same size as the input images.
ocl::StereoBM_OCL::checkIfGpuCallReasonable
-----------------------------------------------
Uses a heuristic method to estimate whether the current GPU is faster than the CPU in this algorithm. It queries the currently active device.
.. ocv:function:: bool ocl::StereoBM_OCL::checkIfGpuCallReasonable()
ocl::StereoBeliefPropagation
--------------------------------
.. ocv:class:: ocl::StereoBeliefPropagation
Class computing stereo correspondence using the belief propagation algorithm. ::
class CV_EXPORTS StereoBeliefPropagation
{
public:
enum { DEFAULT_NDISP = 64 };
enum { DEFAULT_ITERS = 5 };
enum { DEFAULT_LEVELS = 5 };
static void estimateRecommendedParams(int width, int height, int &ndisp, int &iters, int &levels);
explicit StereoBeliefPropagation(int ndisp = DEFAULT_NDISP,
int iters = DEFAULT_ITERS,
int levels = DEFAULT_LEVELS,
int msg_type = CV_16S);
StereoBeliefPropagation(int ndisp, int iters, int levels,
float max_data_term, float data_weight,
float max_disc_term, float disc_single_jump,
int msg_type = CV_32F);
void operator()(const oclMat &left, const oclMat &right, oclMat &disparity);
void operator()(const oclMat &data, oclMat &disparity);
int ndisp;
int iters;
int levels;
float max_data_term;
float data_weight;
float max_disc_term;
float disc_single_jump;
int msg_type;
private:
/* hidden */
};
The class implements algorithm described in [Felzenszwalb2006]_ . It can compute own data cost (using a truncated linear model) or use a user-provided data cost.
.. note::
``StereoBeliefPropagation`` requires a lot of memory for message storage:
.. math::
width \_ step \cdot height \cdot ndisp \cdot 4 \cdot (1 + 0.25)
and for data cost storage:
.. math::
width\_step \cdot height \cdot ndisp \cdot (1 + 0.25 + 0.0625 + \dotsm + \frac{1}{4^{levels}})
``width_step`` is the number of bytes in a line including padding.
ocl::StereoBeliefPropagation::StereoBeliefPropagation
---------------------------------------------------------
Enables the :ocv:class:`ocl::StereoBeliefPropagation` constructors.
.. ocv:function:: ocl::StereoBeliefPropagation::StereoBeliefPropagation(int ndisp = DEFAULT_NDISP, int iters = DEFAULT_ITERS, int levels = DEFAULT_LEVELS, int msg_type = CV_16S)
.. ocv:function:: ocl::StereoBeliefPropagation::StereoBeliefPropagation(int ndisp, int iters, int levels, float max_data_term, float data_weight, float max_disc_term, float disc_single_jump, int msg_type = CV_32F)
:param ndisp: Number of disparities.
:param iters: Number of BP iterations on each level.
:param levels: Number of levels.
:param max_data_term: Threshold for data cost truncation.
:param data_weight: Data weight.
:param max_disc_term: Threshold for discontinuity truncation.
:param disc_single_jump: Discontinuity single jump.
:param msg_type: Type for messages. ``CV_16SC1`` and ``CV_32FC1`` types are supported.
``StereoBeliefPropagation`` uses a truncated linear model for the data cost and discontinuity terms:
.. math::
DataCost = data \_ weight \cdot \min ( \lvert Img_Left(x,y)-Img_Right(x-d,y) \rvert , max \_ data \_ term)
.. math::
DiscTerm = \min (disc \_ single \_ jump \cdot \lvert f_1-f_2 \rvert , max \_ disc \_ term)
For more details, see [Felzenszwalb2006]_.
By default, :ocv:class:`ocl::StereoBeliefPropagation` uses floating-point arithmetics and the ``CV_32FC1`` type for messages. But it can also use fixed-point arithmetics and the ``CV_16SC1`` message type for better performance. To avoid an overflow in this case, the parameters must satisfy the following requirement:
.. math::
10 \cdot 2^{levels-1} \cdot max \_ data \_ term < SHRT \_ MAX
ocl::StereoBeliefPropagation::estimateRecommendedParams
-----------------------------------------------------------
Uses a heuristic method to compute the recommended parameters ( ``ndisp``, ``iters`` and ``levels`` ) for the specified image size ( ``width`` and ``height`` ).
.. ocv:function:: void ocl::StereoBeliefPropagation::estimateRecommendedParams(int width, int height, int& ndisp, int& iters, int& levels)
ocl::StereoBeliefPropagation::operator ()
---------------------------------------------
Enables the stereo correspondence operator that finds the disparity for the specified rectified stereo pair or data cost.
.. ocv:function:: void ocl::StereoBeliefPropagation::operator ()(const oclMat& left, const oclMat& right, oclMat& disparity)
.. ocv:function:: void ocl::StereoBeliefPropagation::operator ()(const oclMat& data, oclMat& disparity)
:param left: Left image. ``CV_8UC1`` , ``CV_8UC3`` and ``CV_8UC4`` types are supported.
:param right: Right image with the same size and the same type as the left one.
:param data: User-specified data cost, a matrix of ``msg_type`` type and ``Size(<image columns>*ndisp, <image rows>)`` size.
:param disparity: Output disparity map. If ``disparity`` is empty, the output type is ``CV_16SC1`` . Otherwise, the type is retained.
ocl::StereoConstantSpaceBP
------------------------------
.. ocv:class:: ocl::StereoConstantSpaceBP
Class computing stereo correspondence using the constant space belief propagation algorithm. ::
class CV_EXPORTS StereoConstantSpaceBP
{
public:
enum { DEFAULT_NDISP = 128 };
enum { DEFAULT_ITERS = 8 };
enum { DEFAULT_LEVELS = 4 };
enum { DEFAULT_NR_PLANE = 4 };
static void estimateRecommendedParams(int width, int height, int &ndisp, int &iters, int &levels, int &nr_plane);
explicit StereoConstantSpaceBP(
int ndisp = DEFAULT_NDISP,
int iters = DEFAULT_ITERS,
int levels = DEFAULT_LEVELS,
int nr_plane = DEFAULT_NR_PLANE,
int msg_type = CV_32F);
StereoConstantSpaceBP(int ndisp, int iters, int levels, int nr_plane,
float max_data_term, float data_weight, float max_disc_term, float disc_single_jump,
int min_disp_th = 0,
int msg_type = CV_32F);
void operator()(const oclMat &left, const oclMat &right, oclMat &disparity);
int ndisp;
int iters;
int levels;
int nr_plane;
float max_data_term;
float data_weight;
float max_disc_term;
float disc_single_jump;
int min_disp_th;
int msg_type;
bool use_local_init_data_cost;
private:
/* hidden */
};
The class implements algorithm described in [Yang2010]_. ``StereoConstantSpaceBP`` supports both local minimum and global minimum data cost initialization algorithms. For more details, see the paper mentioned above. By default, a local algorithm is used. To enable a global algorithm, set ``use_local_init_data_cost`` to ``false`` .
ocl::StereoConstantSpaceBP::StereoConstantSpaceBP
-----------------------------------------------------
Enables the :ocv:class:`ocl::StereoConstantSpaceBP` constructors.
.. ocv:function:: ocl::StereoConstantSpaceBP::StereoConstantSpaceBP(int ndisp = DEFAULT_NDISP, int iters = DEFAULT_ITERS, int levels = DEFAULT_LEVELS, int nr_plane = DEFAULT_NR_PLANE, int msg_type = CV_32F)
.. ocv:function:: ocl::StereoConstantSpaceBP::StereoConstantSpaceBP(int ndisp, int iters, int levels, int nr_plane, float max_data_term, float data_weight, float max_disc_term, float disc_single_jump, int min_disp_th = 0, int msg_type = CV_32F)
:param ndisp: Number of disparities.
:param iters: Number of BP iterations on each level.
:param levels: Number of levels.
:param nr_plane: Number of disparity levels on the first level.
:param max_data_term: Truncation of data cost.
:param data_weight: Data weight.
:param max_disc_term: Truncation of discontinuity.
:param disc_single_jump: Discontinuity single jump.
:param min_disp_th: Minimal disparity threshold.
:param msg_type: Type for messages. ``CV_16SC1`` and ``CV_32FC1`` types are supported.
``StereoConstantSpaceBP`` uses a truncated linear model for the data cost and discontinuity terms:
.. math::
DataCost = data \_ weight \cdot \min ( \lvert I_2-I_1 \rvert , max \_ data \_ term)
.. math::
DiscTerm = \min (disc \_ single \_ jump \cdot \lvert f_1-f_2 \rvert , max \_ disc \_ term)
For more details, see [Yang2010]_.
By default, ``StereoConstantSpaceBP`` uses floating-point arithmetics and the ``CV_32FC1`` type for messages. But it can also use fixed-point arithmetics and the ``CV_16SC1`` message type for better performance. To avoid an overflow in this case, the parameters must satisfy the following requirement:
.. math::
10 \cdot 2^{levels-1} \cdot max \_ data \_ term < SHRT \_ MAX
ocl::StereoConstantSpaceBP::estimateRecommendedParams
---------------------------------------------------------
Uses a heuristic method to compute parameters (ndisp, iters, levelsand nrplane) for the specified image size (widthand height).
.. ocv:function:: void ocl::StereoConstantSpaceBP::estimateRecommendedParams(int width, int height, int& ndisp, int& iters, int& levels, int& nr_plane)
ocl::StereoConstantSpaceBP::operator ()
-------------------------------------------
Enables the stereo correspondence operator that finds the disparity for the specified rectified stereo pair.
.. ocv:function:: void ocl::StereoConstantSpaceBP::operator ()(const oclMat& left, const oclMat& right, oclMat& disparity)
:param left: Left image. ``CV_8UC1`` , ``CV_8UC3`` and ``CV_8UC4`` types are supported.
:param right: Right image with the same size and the same type as the left one.
:param disparity: Output disparity map. If ``disparity`` is empty, the output type is ``CV_16SC1`` . Otherwise, the output type is ``disparity.type()`` .