3 research outputs found
Minimal Solvers for Single-View Lens-Distorted Camera Auto-Calibration
This paper proposes minimal solvers that use combinations of imaged
translational symmetries and parallel scene lines to jointly estimate lens
undistortion with either affine rectification or focal length and absolute
orientation. We use constraints provided by orthogonal scene planes to recover
the focal length. We show that solvers using feature combinations can recover
more accurate calibrations than solvers using only one feature type on scenes
that have a balance of lines and texture. We also show that the proposed
solvers are complementary and can be used together in a RANSAC-based estimator
to improve auto-calibration accuracy. State-of-the-art performance is
demonstrated on a standard dataset of lens-distorted urban images. The code is
available at https://github.com/ylochman/single-view-autocalib
Optimal Multi-view Correction of Local Affine Frames
The technique requires the epipolar geometry to be pre-estimated between each
image pair. It exploits the constraints which the camera movement implies, in
order to apply a closed-form correction to the parameters of the input
affinities. Also, it is shown that the rotations and scales obtained by
partially affine-covariant detectors, e.g., AKAZE or SIFT, can be completed to
be full affine frames by the proposed algorithm. It is validated both in
synthetic experiments and on publicly available real-world datasets that the
method always improves the output of the evaluated affine-covariant feature
detectors. As a by-product, these detectors are compared and the ones obtaining
the most accurate affine frames are reported. For demonstrating the
applicability, we show that the proposed technique as a pre-processing step
improves the accuracy of pose estimation for a camera rig, surface normal and
homography estimation
Improving the A-Contrario computation of a fundamental matrix in computer vision
Laboratoire MAP5 (Mathématiques appliquées Paris 5), CNRS UMR8145 Université Paris V - Paris DescartesThe fundamental matrix is a two-view tensor playing a central role in Computer Vision geometry. We address its robust estimation given pairs of matched image features, affected by noise and outliers, which searches for a maximal subset of correct matches and the associated fundamental matrix. Overcoming the broadly used parametric RANSAC method, ORSA follows a probabilistic a contrario approach to look for the set of matches being least expected with respect to a uniform random distribution of image points. ORSA lacks performance when this assumption is clearly violated. We will propose an improvement of the ORSA method, based on its same a contrario framework and the use of a non-parametric estimate of the distribution of image features. The role and estimation of the fundamental matrix and the data SIFT matches will be carefully explained with examples. Our proposal performs significantly well for common scenarios of low inlier ratios and local feature concentrations