t_tracking.h

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// Copyright 2019-2023, Collabora, Ltd.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  Tracking API interface.
 * @author Pete Black <pblack@collabora.com>
 * @author Jakob Bornecrantz <jakob@collabora.com>
 * @author Rylie Pavlik <rylie.pavlik@collabora.com>
 * @author Moshi Turner <moshiturner@protonmail.com>
 * @ingroup aux_tracking
 */
 
#pragma once
 
#include "util/u_logging.h"
#include "xrt/xrt_defines.h"
#include "xrt/xrt_frame.h"
#include "xrt/xrt_tracking.h"
#include "util/u_misc.h"
 
#include <stdio.h>
 
 
#ifdef __cplusplus
extern "C" {
#endif
 
/*!
 * @addtogroup aux_tracking
 * @{
 */
 
 
/*
 *
 * Pre-declare
 *
 */
 
typedef struct cJSON cJSON;
struct xrt_slam_sinks;
struct xrt_tracked_psmv;
struct xrt_tracked_psvr;
struct xrt_tracked_slam;
 
 
/*
 *
 * Calibration data.
 *
 */
 
//! Maximum size of rectilinear distortion coefficient array
#define XRT_DISTORTION_MAX_DIM (14)
 
/*!
 * @brief The distortion model this camera calibration falls under.
 * @todo Add RiftS's Fisheye62 to this enumerator once we have native support for it in our hand tracking and SLAM.
 * @todo Feel free to add support for T_DISTORTION_OPENCV_RADTAN_4 or T_DISTORTION_OPENCV_RADTAN_12 whenever you have a
 * camera that uses those.
 */
enum t_camera_distortion_model
{
        /*!
         * A perfect pinhole camera with no distortion.
         */
        T_DISTORTION_PINHOLE,
 
        /*!
         * OpenCV's radial-tangential distortion model. Exactly equivalent to the distortion model from OpenCV's calib3d
         * module with just the first five parameters. This may be reinterpreted as RT8 with the last three parameters
         * zeroed out, which is 100% valid and results in exactly equivalent (un)projections.
         *
         * Parameters:
         *
         * \f[(k_1, k_2, p_1, p_2, k_3)\f]
         */
        T_DISTORTION_OPENCV_RADTAN_5,
 
        /*!
         * OpenCV's radial-tangential distortion model. Exactly equivalent to the distortion model from OpenCV's calib3d
         * module, with just the first 8 parameters.
         * Parameters:
         *
         * \f[(k_1, k_2, p_1, p_2, k_3, k_4, k_5, k_6)\f]
         */
        T_DISTORTION_OPENCV_RADTAN_8,
 
        /*!
         * OpenCV's radial-tangential distortion model. Exactly equivalent to the distortion model from OpenCV's calib3d
         * module, with all 14 parameters.
         *
         * In practice this is reinterpreted as RT8 because the last 6 parameters are almost always approximately 0.
         *
         * @todo Feel free to implement RT14 (un)projection functions if you have a camera that actually has a tilted
         * sensor.
         *
         * Parameters:
         *
         * \f[(k_1, k_2, p_1, p_2, k_3, k_4, k_5, k_6, s_1, s_2, s_3, s_4, \tau_x, \tau_y)\f]
         *
         * All known factory-calibrated Luxonis cameras use this distortion model, and in all known cases their last 6
         * parameters are approximately 0.
         *
         */
        T_DISTORTION_OPENCV_RADTAN_14,
 
        /*!
         * Juho Kannalla and Sami Sebastian Brandt's fisheye distortion model. Exactly equivalent to the distortion
         * model from OpenCV's calib3d/fisheye module.
         *
         * Parameters:
         *
         * \f[(k_1, k_2, k_3, k_4)\f]
         *
         * Many cameras use this model. Here's a non-exhaustive list of cameras Monado knows about that fall under this
         * model:
         * * Intel T265
         * * Valve Index
         */
        T_DISTORTION_FISHEYE_KB4,
 
        /*!
         * Windows Mixed Reality headsets' camera model.
         *
         * The model is listed as CALIBRATION_LensDistortionModelRational6KT in the WMR json files, which seems to be
         * equivalent to Azure-Kinect-Sensor-SDK's K4A_CALIBRATION_LENS_DISTORTION_MODEL_RATIONAL_6KT.
         *
         * The only difference between this model and RT8 are codx, cody, and the way p1 and p2 are interpreted. In
         * practice we reinterpret this as RT8 because those values are almost always approximately 0 for WMR headsets.
         *
         * Parameters:
         *
         * \f[(k_1, k_2, p_1, p_2, k_3, k_4, k_5, k_6, cod_x, cod_y, rpmax)\f]
         */
        T_DISTORTION_WMR,
 
        /*!
         * The Oculus Rift CV1 constellation sensor's lens model (LensModel "type 6" in Oculus'
         * runtime). Despite superficially resembling Kannala-Brandt, it is a distinct model: the
         * normalized image radius @p r is used *directly* as the field angle and passed through
         * @p tan, rather than KB's \f$\theta = \operatorname{atan}(r)\f$. It also carries tangential
         * decentering and a 4th-order affine gain on that decentering, which KB4 lacks.
         *
         * Parameters:
         *
         * \f[(k_1, k_2, k_3, k_4, p_1, p_2, g_3, g_4)\f]
         */
        T_DISTORTION_RIFT_CV1,
};
 
 
/*!
 * Stringifies a @ref t_camera_distortion_model
 * @param model The distortion model to be stringified
 * @return The distortion model as a string
 */
static inline const char *
t_stringify_camera_distortion_model(const enum t_camera_distortion_model model)
{
        switch (model) {
        case T_DISTORTION_PINHOLE: return "T_DISTORTION_PINHOLE"; break;
        case T_DISTORTION_OPENCV_RADTAN_5: return "T_DISTORTION_OPENCV_RADTAN_5"; break;
        case T_DISTORTION_OPENCV_RADTAN_8: return "T_DISTORTION_OPENCV_RADTAN_8"; break;
        case T_DISTORTION_OPENCV_RADTAN_14: return "T_DISTORTION_OPENCV_RADTAN_14"; break;
        case T_DISTORTION_WMR: return "T_DISTORTION_WMR"; break;
        case T_DISTORTION_FISHEYE_KB4: return "T_DISTORTION_FISHEYE_KB4"; break;
        case T_DISTORTION_RIFT_CV1: return "T_DISTORTION_RIFT_CV1"; break;
        default: U_LOG_E("Invalid distortion_model! %d", model); return "INVALID";
        }
}
 
/*!
 * Returns the number of parameters needed for this @ref t_camera_distortion_model to be held by an OpenCV Mat and
 * correctly interpreted by OpenCV's (un)projection functions.
 *
 * @param model The distortion model in question
 * @return The number of distortion coefficients, or 0 if this model cannot be represented inside OpenCV.
 */
static inline size_t
t_num_params_from_distortion_model(const enum t_camera_distortion_model model)
{
        switch (model) {
        case T_DISTORTION_PINHOLE: return 0; break;
        case T_DISTORTION_OPENCV_RADTAN_5: return 5; break;
        case T_DISTORTION_OPENCV_RADTAN_8: return 8; break;
        case T_DISTORTION_OPENCV_RADTAN_14: return 14; break;
        case T_DISTORTION_WMR: return 11; break;
        case T_DISTORTION_FISHEYE_KB4: return 4; break;
        case T_DISTORTION_RIFT_CV1: return 8; break; // k1..k4, p1, p2, g3, g4
        default: U_LOG_E("Invalid distortion_model! %d", model); return 0;
        }
}
 
static inline bool
t_camera_distortion_model_is_fisheye(enum t_camera_distortion_model model)
{
        switch (model) {
        case T_DISTORTION_FISHEYE_KB4:
        case T_DISTORTION_RIFT_CV1: return true;
        case T_DISTORTION_PINHOLE:
        case T_DISTORTION_OPENCV_RADTAN_5:
        case T_DISTORTION_OPENCV_RADTAN_8:
        case T_DISTORTION_OPENCV_RADTAN_14:
        case T_DISTORTION_WMR: return false;
        default: U_LOG_E("Invalid distortion_model! %d", model); return false;
        }
}
 
/*!
 * Parameters for @ref T_DISTORTION_OPENCV_RADTAN_5
 * @ingroup aux_tracking
 */
struct t_camera_calibration_rt5_params
{
        double k1, k2, p1, p2, k3;
};
 
/*!
 * Parameters for @ref T_DISTORTION_OPENCV_RADTAN_8
 * @ingroup aux_tracking
 */
struct t_camera_calibration_rt8_params
{
        double k1, k2, p1, p2, k3, k4, k5, k6;
};
 
/*!
 * Parameters for @ref T_DISTORTION_OPENCV_RADTAN_14
 * @ingroup aux_tracking
 */
struct t_camera_calibration_rt14_params
{
        double k1, k2, p1, p2, k3, k4, k5, k6, s1, s2, s3, s4, tx, ty;
};
 
/*!
 * Parameters for @ref T_DISTORTION_FISHEYE_KB4
 * @ingroup aux_tracking
 */
struct t_camera_calibration_kb4_params
{
        double k1, k2, k3, k4;
};
 
/*!
 * Parameters for @ref T_DISTORTION_WMR
 * @ingroup aux_tracking
 */
struct t_camera_calibration_wmr_params
{
        double k1, k2, p1, p2, k3, k4, k5, k6, codx, cody, rpmax;
};
 
/*!
 * Parameters for @ref T_DISTORTION_RIFT_CV1
 * @ingroup aux_tracking
 */
struct t_camera_calibration_cv1_params
{
        double k1, k2, k3, k4, p1, p2, g3, g4;
};
 
/*!
 * @brief Essential calibration data for a single camera, or single lens/sensor
 * of a stereo camera.
 */
struct t_camera_calibration
{
        //! Source image size
        struct xrt_size image_size_pixels;
 
        //! Camera intrinsics matrix
        double intrinsics[3][3];
 
        union {
                struct t_camera_calibration_rt5_params rt5;
                struct t_camera_calibration_rt8_params rt8;
                struct t_camera_calibration_rt14_params rt14;
                struct t_camera_calibration_kb4_params kb4;
                struct t_camera_calibration_wmr_params wmr;
                struct t_camera_calibration_cv1_params cv1;
                double distortion_parameters_as_array[XRT_DISTORTION_MAX_DIM];
        };
 
        //! Distortion model that this camera uses.
        enum t_camera_distortion_model distortion_model;
};
 
/*!
 * Fills in a basic intrinsics matrix using the standard set of parameters.
 */
static inline void
t_camera_calibration_fill_intrinsics(
    struct t_camera_calibration *calibration, double fx, double fy, double cx, double cy)
{
        double intrinsics[3][3] = {
            // clang-format off
            {fx,  0.0, cx},
            {0.0, fy,  cy},
            {0.0, 0.0, 1.0},
            // clang-format on
        };
 
        memcpy(calibration->intrinsics, intrinsics, sizeof(intrinsics));
}
 
/*!
 * Stereo camera calibration data to be given to trackers.
 */
struct t_stereo_camera_calibration
{
        //! Ref counting
        struct xrt_reference reference;
 
        //! Calibration of individual views/sensor
        struct t_camera_calibration view[2];
 
        //! Translation from first to second in the stereo pair.
        double camera_translation[3];
        //! Rotation matrix from first to second in the stereo pair.
        double camera_rotation[3][3];
 
        //! Essential matrix.
        double camera_essential[3][3];
        //! Fundamental matrix.
        double camera_fundamental[3][3];
};
 
/*!
 * Allocates a new stereo calibration data, unreferences the old data pointed to by @p out_c.
 *
 * @public @memberof t_stereo_camera_calibration
 */
void
t_stereo_camera_calibration_alloc(struct t_stereo_camera_calibration **out_c,
                                  const enum t_camera_distortion_model distortion_model);
 
/*!
 * Only to be called by @p t_stereo_camera_calibration_reference.
 *
 * @private @memberof t_stereo_camera_calibration
 */
void
t_stereo_camera_calibration_destroy(struct t_stereo_camera_calibration *c);
 
/*!
 * Update the reference counts on a stereo calibration data(s).
 *
 * @param[in,out] dst Pointer to a object reference: if the object reference is
 *                non-null will decrement its counter. The reference that
 *                @p dst points to will be set to @p src.
 * @param[in] src New object for @p dst to refer to (may be null).
 *                If non-null, will have its refcount increased.
 *
 * @relates t_stereo_camera_calibration
 */
static inline void
t_stereo_camera_calibration_reference(struct t_stereo_camera_calibration **dst, struct t_stereo_camera_calibration *src)
{
        struct t_stereo_camera_calibration *old_dst = *dst;
 
        if (old_dst == src) {
                return;
        }
 
        if (src) {
                xrt_reference_inc(&src->reference);
        }
 
        *dst = src;
 
        if (old_dst) {
                if (xrt_reference_dec_and_is_zero(&old_dst->reference)) {
                        t_stereo_camera_calibration_destroy(old_dst);
                }
        }
}
 
/*!
 * Small helper function that dumps one camera calibration data to logging.
 *
 * @relates t_camera_calibration
 */
void
t_camera_calibration_dump(struct t_camera_calibration *c);
 
/*!
 * Small helper function that dumps the stereo calibration data to logging.
 *
 * @relates t_stereo_camera_calibration
 */
void
t_stereo_camera_calibration_dump(struct t_stereo_camera_calibration *c);
 
/*!
 * Load stereo calibration data from a given file in v1 format (binary).
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_load_v1(FILE *calib_file, struct t_stereo_camera_calibration **out_data);
 
/*!
 * Save the given stereo calibration data to the given file in v1 format (binary).
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_save_v1(FILE *calib_file, struct t_stereo_camera_calibration *data);
 
/*!
 * Parse the json object in v2 format into stereo calibration data.
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_from_json_v2(cJSON *json, struct t_stereo_camera_calibration **out_stereo);
 
/*!
 * Convert the given stereo calibration data into a json object in v2 format.
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_to_json_v2(cJSON **out_cjson, struct t_stereo_camera_calibration *data);
 
 
/*!
 * Load stereo calibration data from a given file path.
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_load(const char *calib_path, struct t_stereo_camera_calibration **out_data);
 
/*!
 * Save the given stereo calibration data to the given file path.
 *
 * @relates t_stereo_camera_calibration
 */
bool
t_stereo_camera_calibration_save(const char *calib_path, struct t_stereo_camera_calibration *data);
 
 
/*
 *
 * IMU calibration data.
 *
 */
 
/*!
 * @brief Parameters for accelerometer and gyroscope calibration.
 * @see slam_tracker::imu_calibration for a more detailed description and references.
 */
struct t_inertial_calibration
{
        //! Linear transformation for raw measurements alignment and scaling.
        double transform[3][3];
 
        //! Offset to apply to raw measurements.
        double offset[3];
 
        //! Modeled sensor bias. @see slam_tracker::imu_calibration.
        double bias_std[3];
 
        //! Modeled measurement noise. @see slam_tracker::imu_calibration.
        double noise_std[3];
};
 
/*!
 * @brief Combined IMU calibration data.
 */
struct t_imu_calibration
{
        //! Accelerometer calibration data.
        struct t_inertial_calibration accel;
 
        //! Gyroscope calibration data.
        struct t_inertial_calibration gyro;
};
/*!
 * Prints a @ref t_inertial_calibration struct
 *
 * @relates t_camera_calibration
 */
void
t_inertial_calibration_dump(struct t_inertial_calibration *c);
 
/*!
 * Small helper function that dumps the imu calibration data to logging.
 *
 * @relates t_camera_calibration
 */
void
t_imu_calibration_dump(struct t_imu_calibration *c);
 
 
/*
 *
 * Conversion functions.
 *
 */
 
struct t_convert_table
{
        uint8_t v[256][256][256][3]; // nolint(readability-magic-numbers)
};
 
void
t_convert_fill_table(struct t_convert_table *t);
 
void
t_convert_make_y8u8v8_to_r8g8b8(struct t_convert_table *t);
 
void
t_convert_make_y8u8v8_to_h8s8v8(struct t_convert_table *t);
 
void
t_convert_make_h8s8v8_to_r8g8b8(struct t_convert_table *t);
 
void
t_convert_in_place_y8u8v8_to_r8g8b8(uint32_t width, uint32_t height, size_t stride, void *data_ptr);
 
void
t_convert_in_place_y8u8v8_to_h8s8v8(uint32_t width, uint32_t height, size_t stride, void *data_ptr);
 
void
t_convert_in_place_h8s8v8_to_r8g8b8(uint32_t width, uint32_t height, size_t stride, void *data_ptr);
 
 
/*
 *
 * Filter functions.
 *
 */
 
#define T_HSV_SIZE 32
#define T_HSV_STEP (256 / T_HSV_SIZE)
 
// @todo Remove this when clang-format is updated in CI
// clang-format off
#define T_HSV_DEFAULT_PARAMS()                                                                                         \
        {                                                                                                              \
            {                                                                                                          \
                {165, 30, 160, 100},                                                                                   \
                {135, 30, 160, 100},                                                                                   \
                {95, 30, 160, 100},                                                                                    \
            },                                                                                                         \
            {128, 80},                                                                                                 \
        }
// clang-format on
 
struct t_hsv_filter_color
{
        uint8_t hue_min;
        uint8_t hue_range;
 
        uint8_t s_min;
 
        uint8_t v_min;
};
 
/*!
 * Parameters for constructing an HSV filter.
 * @relates t_hsv_filter
 */
struct t_hsv_filter_params
{
        struct t_hsv_filter_color color[3];
 
        struct
        {
                uint8_t s_max;
                uint8_t v_min;
        } white;
};
 
struct t_hsv_filter_large_table
{
        uint8_t v[256][256][256];
};
 
struct t_hsv_filter_optimized_table
{
        uint8_t v[T_HSV_SIZE][T_HSV_SIZE][T_HSV_SIZE];
};
 
void
t_hsv_build_convert_table(struct t_hsv_filter_params *params, struct t_convert_table *t);
 
void
t_hsv_build_large_table(struct t_hsv_filter_params *params, struct t_hsv_filter_large_table *t);
 
void
t_hsv_build_optimized_table(struct t_hsv_filter_params *params, struct t_hsv_filter_optimized_table *t);
 
static inline uint8_t
t_hsv_filter_sample(struct t_hsv_filter_optimized_table *t, uint32_t y, uint32_t u, uint32_t v)
{
        return t->v[y / T_HSV_STEP][u / T_HSV_STEP][v / T_HSV_STEP];
}
 
/*!
 * Construct an HSV filter sink.
 * @public @memberof t_hsv_filter
 *
 * @see xrt_frame_context
 */
int
t_hsv_filter_create(struct xrt_frame_context *xfctx,
                    struct t_hsv_filter_params *params,
                    struct xrt_frame_sink *sinks[4],
                    struct xrt_frame_sink **out_sink);
 
 
/*
 *
 * Tracker code.
 *
 */
 
/*!
 * @public @memberof xrt_tracked_psmv
 */
int
t_psmv_start(struct xrt_tracked_psmv *xtmv);
 
/*!
 * @public @memberof xrt_tracked_psmv
 */
int
t_psmv_create(struct xrt_frame_context *xfctx,
              struct xrt_colour_rgb_f32 *rgb,
              struct t_stereo_camera_calibration *data,
              struct xrt_tracked_psmv **out_xtmv,
              struct xrt_frame_sink **out_sink);
 
/*!
 * @public @memberof xrt_tracked_psvr
 */
int
t_psvr_start(struct xrt_tracked_psvr *xtvr);
 
/*!
 * @public @memberof xrt_tracked_psvr
 */
int
t_psvr_create(struct xrt_frame_context *xfctx,
              struct t_stereo_camera_calibration *data,
              struct xrt_tracked_psvr **out_xtvr,
              struct xrt_frame_sink **out_sink);
 
 
 
/*!
 * SLAM prediction type. Naming scheme as follows:
 * P: position, O: orientation, A: angular velocity, L: linear velocity
 * S: From SLAM poses (slow, precise), I: From IMU data (fast, noisy)
 *
 * @see xrt_tracked_slam
 */
enum t_slam_prediction_type
{
        SLAM_PRED_NONE = 0,       //!< No prediction, always return the last SLAM tracked pose
        SLAM_PRED_POSE_ONLY,      //!< Predicts from last two SLAM poses only
        SLAM_PRED_GYRO,           //!< Predicts from last SLAM pose with angular velocity computed from IMU
        SLAM_PRED_ACCEL_GYRO,     //!< Predicts from last SLAM pose with angular and linear velocity computed from IMU
        SLAM_PRED_DEAD_RECKONING, //!< Predicts from a pose that is the last SLAM pose with the IMU samples that came
                                  //!< after it integrated on top; velocities from latest IMU sample.
        SLAM_PRED_COUNT,
};
 
/*!
 * Extension to camera calibration for SLAM tracking
 *
 * @see xrt_tracked_slam
 */
struct t_slam_camera_calibration
{
        struct t_camera_calibration base;
        struct xrt_matrix_4x4 T_imu_cam; //!< Transform IMU to camera. Column major.
        double frequency;                //!< Camera FPS
};
 
/*!
 * Extension to IMU calibration for SLAM tracking
 *
 * @see xrt_tracked_slam
 */
struct t_slam_imu_calibration
{
        struct t_imu_calibration base;
        double frequency;
};
 
/*!
 * Calibration information necessary for SLAM tracking.
 *
 * @see xrt_tracked_slam
 */
struct t_slam_calibration
{
        struct t_slam_imu_calibration imu;                            //!< IMU calibration data
        struct t_slam_camera_calibration cams[XRT_TRACKING_MAX_CAMS]; //!< Calib data of `cam_count` cams
        int cam_count;                                                //!< Number of cameras
};
 
/*!
 * SLAM tracker configuration.
 *
 * @see xrt_tracked_slam
 */
struct t_slam_tracker_config
{
        enum u_logging_level log_level;      //!< SLAM tracking logging level
        const char *vit_system_library_path; //!< Path to the VIT system library
        const char *slam_config;             //!< Config file path, format is specific to the SLAM implementation in use
        int cam_count;                       //!< Number of cameras in use
        bool slam_ui;                        //!< Whether to open the external UI of the external SLAM system
        bool submit_from_start;              //!< Whether to submit data to the SLAM tracker without user action
        int openvr_groundtruth_device;       //!< If >0, use lighthouse as groundtruth, see @ref openvr_device
        enum t_slam_prediction_type prediction; //!< Which level of prediction to use
        bool write_csvs;                        //!< Whether to enable CSV writers from the start for later analysis
        const char *csv_path;                   //!< Path to write CSVs to
        bool timing_stat;                       //!< Enable timing metric in external system
        bool features_stat;                     //!< Enable feature metric in external system
 
        //!< Instead of a slam_config file you can set custom calibration data
        const struct t_slam_calibration *slam_calib;
};
 
/*!
 * Fills in a @ref t_slam_tracker_config with default values.
 *
 * @see xrt_tracked_Slam
 */
void
t_slam_fill_default_config(struct t_slam_tracker_config *config);
 
/*!
 * @public @memberof xrt_tracked_slam
 */
int
t_slam_create(struct xrt_frame_context *xfctx,
              struct t_slam_tracker_config *config,
              struct xrt_tracked_slam **out_xts,
              struct xrt_slam_sinks **out_sink);
 
/*!
 * @public @memberof xrt_tracked_slam
 */
int
t_slam_start(struct xrt_tracked_slam *xts);
 
/*
 *
 * Camera calibration
 *
 */
 
/*!
 * Board pattern type.
 */
enum t_board_pattern
{
        T_BOARD_CHECKERS,
        //! Sector based checker board, using `cv::findChessboardCornersSB`.
        T_BOARD_SB_CHECKERS,
        T_BOARD_CIRCLES,
        T_BOARD_ASYMMETRIC_CIRCLES,
};
 
struct t_calibration_status
{
        //! Is calibration finished?
        bool finished;
        //! Was the target found this frame?
        bool found;
        //! Number of frames collected
        int num_collected;
        //! Number of moving frames before another capture
        int cooldown;
        //! Number of non-moving frames before capture.
        int waits_remaining;
        //! Stereo calibration data that was produced.
        struct t_stereo_camera_calibration *stereo_data;
};
 
struct t_calibration_params
{
        //! Should we use fisheye version of the calibration functions.
        bool use_fisheye;
        //! Is the camera a stereo sbs camera, mostly for image loading.
        bool stereo_sbs;
        //! What type of pattern are we using for calibration.
        enum t_board_pattern pattern;
 
        struct
        {
                int cols;
                int rows;
                float size_meters;
 
                bool subpixel_enable;
                int subpixel_size;
        } checkers;
 
        struct
        {
                int cols;
                int rows;
                float size_meters;
 
                bool marker;
                bool normalize_image;
        } sb_checkers;
 
        struct
        {
                int cols;
                int rows;
                float distance_meters;
        } circles;
 
        struct
        {
                int cols;
                int rows;
                float diagonal_distance_meters;
        } asymmetric_circles;
 
        struct
        {
                bool enabled;
                int num_images;
        } load;
 
        int num_cooldown_frames;
        int num_wait_for;
        int num_collect_total;
        int num_collect_restart;
 
        /*!
         * Should we mirror the RGB image?
         *
         * Before text is written out, has no effect on actual image capture.
         */
        bool mirror_rgb_image;
 
        bool save_images;
};
 
/*!
 * Sets the calibration parameters to the their default values.
 * @public @memberof t_calibration_params
 */
void
t_calibration_gui_params_default(struct t_calibration_params *p);
 
void
t_calibration_gui_params_load_or_default(struct t_calibration_params *p);
 
void
t_calibration_gui_params_to_json(cJSON **out_json, struct t_calibration_params *p);
 
void
t_calibration_gui_params_parse_from_json(const cJSON *params, struct t_calibration_params *p);
 
/*!
 * @brief Create the camera calibration frame sink.
 *
 * @param xfctx Context for frame transport.
 * @param params Parameters to use during calibration. Values copied, pointer
 * not retained.
 * @param status Optional pointer to structure for status information. Pointer
 * retained, and pointed-to struct modified.
 * @param gui Frame sink
 * @param out_sink Output: created frame sink.
 *
 * @see xrt_frame_context
 */
int
t_calibration_stereo_create(struct xrt_frame_context *xfctx,
                            const struct t_calibration_params *params,
                            struct t_calibration_status *status,
                            struct xrt_frame_sink *gui,
                            struct xrt_frame_sink **out_sink);
 
 
/*
 *
 * Sink creation functions.
 *
 */
 
/*!
 * @see xrt_frame_context
 */
int
t_convert_yuv_or_yuyv_create(struct xrt_frame_sink *next, struct xrt_frame_sink **out_sink);
 
 
 
/*!
 * @see xrt_frame_context
 */
int
t_debug_hsv_picker_create(struct xrt_frame_context *xfctx,
                          struct xrt_frame_sink *passthrough,
                          struct xrt_frame_sink **out_sink);
 
/*!
 * @see xrt_frame_context
 */
int
t_debug_hsv_viewer_create(struct xrt_frame_context *xfctx,
                          struct xrt_frame_sink *passthrough,
                          struct xrt_frame_sink **out_sink);
 
/*!
 * @see xrt_frame_context
 */
int
t_debug_hsv_filter_create(struct xrt_frame_context *xfctx,
                          struct xrt_frame_sink *passthrough,
                          struct xrt_frame_sink **out_sink);
 
/*!
 * @}
 */
 
 
#ifdef __cplusplus
}
#endif