Traditional algorithms like adaptive histogram
equalization have been employed to enhance low-
light images for better odometry performance (Hao
et al., 2019; Zhang et al., 2022; Gao et al., 2022).
However, these methods often fail to account for vary-
ing illumination within the same image, leading to
suboptimal results. Moreover, contrary to learning-
based approaches, their parameters must be tuned
for specific lighting conditions in most cases. Con-
versely, deep learning approaches like CycleGAN and
generative adversarial networks have been proposed
to enhance low-light images while maintaining struc-
tural consistency between frames (You et al., 2023).
Efforts have also been made to integrate low-light
capabilities directly into odometry estimation neural
networks using binary and deep descriptors (Alismail
et al., 2016), though these studies often lack general-
izability.
3 METHODOLOGY
The methodology employed in this study consists of
several key steps, organized into five functional units
(FUs), as illustrated in Figure 1.
3.1 FU1: Image Darkening
The original KITTI dataset sequences (01, 06, 07,
and 10) were predominantly recorded during daylight,
which does not represent the low-light conditions this
study aims to investigate. To address this, we applied
a gamma transformation to darken the images to sim-
ulate night-time conditions. This method effectively
adjusts the luminance through a non-linear mapping
of pixel intensities, allowing us to retain fine details
while creating the desired low-light effect. The gen-
eral form of gamma transformation is expressed as:
I
out
= c · I
γ
in
, where I
out
denotes the output pixel in-
tensity, c is a scaling constant, typically set to 1 for
simplicity, γ is the gamma correction parameter (we
used gamma value 0.3), and I
in
represents the input
pixel intensity, normalized to the range [0, 1].
3.2 FU2: Image Enhancement
The darkened images were then processed using
four state-of-the-art image enhancement methods:
RetinexFormer, MAXIM, KinD++, and MIRNet. The
purpose of this step was to assess the effect of these
enhancement models on the odometry estimation per-
formance. In Figure 2, one image from KITTI dataset
and its enhanced versions using image processing
methods is shown.
3.3 FU3: Odometry Estimation
We tested the enhanced images using two odometry
estimation models, TartanVO and Selective VIO, to
evaluate their performance in tracking and estimating
pose. These models were chosen for their robustness
in varying environmental conditions and their ability
to handle different image qualities.
3.4 FU4: Edge Enhancement
We observed that in RetinexFormer-enhanced images,
the color channels and image features seemed to dete-
riorate, yet they consistently demonstrated strong per-
formance in many cases. We attributed this to the en-
hancement of edges. To investigate this further, we
explored the impact of edge enhancement on odom-
etry estimation. As the next step in our research, we
applied edge enhancement techniques to the images.
Examples of images enhanced by RetinexFormer are
shown in Figure 3. To enhance edges, we first ap-
plied a Gaussian blur with a sigma value of 2 to re-
duce noise and smooth the image. Then, we used the
Canny edge detector with threshold values of 100 and
200 to identify edges. To make the detected edges
more pronounced, we dilated them using a 3x3 ker-
nel. The edge map, initially in grayscale, was con-
verted to a three-channel image to match the original
image. Finally, we combined the original image with
the edge map by blending them with weights of 1.5
for the original image and -0.5 for the edges, result-
ing in a sharpened image with enhanced edges.
3.5 FU5: Performance Comparison
Finally, the odometry estimation performance across
different image versions was compared the using met-
rics: absolute trajectory error (ATE), relative trans-
lational error (t
rel
), and relative rotational error (r
rel
).
ATE assesses the global accuracy of the estimated tra-
jectory by comparing it to the ground truth, provid-
ing a single error value that summarizes the devia-
tion. t
rel
and r
rel
measure the translation and rotation
errors over specific distances or time intervals, respec-
tively, representing the local accuracy over short tra-
jectory segments. Lower values of ATE, t
rel
, and r
rel
indicate better performance. The analysis in this pa-
per involved a thorough examination of error curves,
evaluation metrics, and speed maps.
Enhancing Visual Odometry Estimation Performance Using Image Enhancement Models
295