C Interface

Beyond the Julia and Python interfaces, we also expose core parts of our library as a ahead-of-time compiled C library using JuliaC.jl. This is currently in a proof-of-concept state since not all public functions are exported, but it will not be hard to expand this once the need is there.

Usage example

A usage example can be found at main.c which we reprint here:

#include "libposeest.h"
#include <stdio.h>
#include <time.h>

int main() {
    WorldPointF64 world_points[] = {
        {0, 50, 0},
        {3000, 50, 0},
        {3000, -50, 0},
        {0, -50, 0},
    };
    ProjectionPointF64 projections[] = {
        {1908.3869731285338, 1413.7171688399328},
        {1982.0042057862263, 1086.0904145429126},
        {2127.0552446444053, 1082.2921194158434},
        {2269.5962158465413, 1404.2585719400536},
    };
    int num_points = 4;

    PoseEstimateF64 pose_result;
    CameraMatrixF64 cammat = {
        // Camera matrix in column-major order (Julia's native layout)
        // Matrix: [fx  0  cx]    Column-major storage: [col1, col2, col3]
        //         [ 0 fy  cy] -> [fx, 0, 0,  0, fy, 0,  cx, cy, 1]
        //         [ 0  0   1]
        {-7246.4, 0.0, 0.0, 0.0, -7246.4, 0.0, 2048.0, 1500.0, 1.0},
        4096.0,
        3000.0};
    WorldPointF64 initial_guess_pos = {-1000, 0, 150};
    RotationF64 initial_guess_rot = {0., 0., 0.};

    int result = estimate_pose_6dof(world_points, projections, num_points, NULL,
                                    COV_DEFAULT, &cammat, &initial_guess_pos,
                                    &initial_guess_rot, &pose_result);

    if (result != POSEEST_SUCCESS) {
        printf("Error: %s\n", get_error_message(result));
        printf("Details: %s\n", get_last_error_detail());
        return 1;
    }

    printf("{\n");
    printf("  \"position\": {\"x\": %.2f, \"y\": %.2f, \"z\": %.2f},\n",
           pose_result.position.x, pose_result.position.y, pose_result.position.z);
    printf("  \"rotation\": {\"yaw\": %.4f, \"pitch\": %.4f, \"roll\": %.4f},\n",
           pose_result.rotation.yaw, pose_result.rotation.pitch, pose_result.rotation.roll);
    printf("  \"residual_norm\": %.6f,\n", pose_result.residual_norm);
    printf("  \"converged\": %s\n", pose_result.converged ? "true" : "false");
    printf("}\n");

    return 0;
}

Next to the main.c file one can find the Makefile which outlines how to compile using the generated C library.