78 research outputs found
Fully Point-wise Convolutional Neural Network for Modeling Statistical Regularities in Natural Images
Modeling statistical regularity plays an essential role in ill-posed image
processing problems. Recently, deep learning based methods have been presented
to implicitly learn statistical representation of pixel distributions in
natural images and leverage it as a constraint to facilitate subsequent tasks,
such as color constancy and image dehazing. However, the existing CNN
architecture is prone to variability and diversity of pixel intensity within
and between local regions, which may result in inaccurate statistical
representation. To address this problem, this paper presents a novel fully
point-wise CNN architecture for modeling statistical regularities in natural
images. Specifically, we propose to randomly shuffle the pixels in the origin
images and leverage the shuffled image as input to make CNN more concerned with
the statistical properties. Moreover, since the pixels in the shuffled image
are independent identically distributed, we can replace all the large
convolution kernels in CNN with point-wise () convolution kernels while
maintaining the representation ability. Experimental results on two
applications: color constancy and image dehazing, demonstrate the superiority
of our proposed network over the existing architectures, i.e., using
1/101/100 network parameters and computational cost while achieving
comparable performance.Comment: 9 pages, 7 figures. To appear in ACM MM 201
Visibility in underwater robotics: Benchmarking and single image dehazing
Dealing with underwater visibility is one of the most important challenges in autonomous underwater robotics. The light transmission in the water medium degrades images making the interpretation of the scene difficult and consequently compromising the whole intervention. This thesis contributes by analysing the impact of the underwater image degradation in commonly used vision algorithms through benchmarking. An online framework for underwater research that makes possible to analyse results under different conditions is presented. Finally, motivated by the results of experimentation with the developed framework, a deep learning solution is proposed capable of dehazing a degraded image in real time restoring the original colors of the image.Una de las dificultades más grandes de la robótica autónoma submarina es lidiar con la falta de visibilidad en imágenes submarinas. La transmisión de la luz en el agua degrada las imágenes dificultando el reconocimiento de objetos y en consecuencia la intervención. Ésta tesis se centra en el análisis del impacto de la degradación de las imágenes submarinas en algoritmos de visión a través de benchmarking, desarrollando un entorno de trabajo en la nube que permite analizar los resultados bajo diferentes condiciones. Teniendo en cuenta los resultados obtenidos con este entorno, se proponen métodos basados en técnicas de aprendizaje profundo para mitigar el impacto de la degradación de las imágenes en tiempo real introduciendo un paso previo que permita recuperar los colores originales
Visibility recovery on images acquired in attenuating media. Application to underwater, fog, and mammographic imaging
136 p.When acquired in attenuating media, digital images of ten suffer from a particularly complex degradation that reduces their visual quality, hindering their suitability for further computational applications, or simply decreasing the visual pleasan tness for the user. In these cases, mathematical image processing reveals it self as an ideal tool to recover some of the information lost during the degradation process. In this dissertation,we deal with three of such practical scenarios in which this problematic is specially relevant, namely, underwater image enhancement, fogremoval and mammographic image processing. In the case of digital mammograms,X-ray beams traverse human tissue, and electronic detectorscapture them as they reach the other side. However, the superposition on a bidimensional image of three-dimensional structures produces low contraste dimages in which structures of interest suffer from a diminished visibility, obstructing diagnosis tasks. Regarding fog removal, the loss of contrast is produced by the atmospheric conditions, and white colour takes over the scene uniformly as distance increases, also reducing visibility.For underwater images, there is an added difficulty, since colour is not lost uniformly; instead, red colours decay the fastest, and green and blue colours typically dominate the acquired images. To address all these challenges,in this dissertation we develop new methodologies that rely on: a)physical models of the observed degradation, and b) the calculus of variations.Equipped with this powerful machinery, we design novel theoreticaland computational tools, including image-dependent functional energies that capture the particularities of each degradation model. These energie sare composed of different integral terms that are simultaneous lyminimized by means of efficient numerical schemes, producing a clean,visually-pleasant and use ful output image, with better contrast and increased visibility. In every considered application, we provide comprehensive qualitative (visual) and quantitative experimental results to validateour methods, confirming that the developed techniques out perform other existing approaches in the literature
Advanced Underwater Image Restoration in Complex Illumination Conditions
Underwater image restoration has been a challenging problem for decades since
the advent of underwater photography. Most solutions focus on shallow water
scenarios, where the scene is uniformly illuminated by the sunlight. However,
the vast majority of uncharted underwater terrain is located beyond 200 meters
depth where natural light is scarce and artificial illumination is needed. In
such cases, light sources co-moving with the camera, dynamically change the
scene appearance, which make shallow water restoration methods inadequate. In
particular for multi-light source systems (composed of dozens of LEDs
nowadays), calibrating each light is time-consuming, error-prone and tedious,
and we observe that only the integrated illumination within the viewing volume
of the camera is critical, rather than the individual light sources. The key
idea of this paper is therefore to exploit the appearance changes of objects or
the seafloor, when traversing the viewing frustum of the camera. Through new
constraints assuming Lambertian surfaces, corresponding image pixels constrain
the light field in front of the camera, and for each voxel a signal factor and
a backscatter value are stored in a volumetric grid that can be used for very
efficient image restoration of camera-light platforms, which facilitates
consistently texturing large 3D models and maps that would otherwise be
dominated by lighting and medium artifacts. To validate the effectiveness of
our approach, we conducted extensive experiments on simulated and real-world
datasets. The results of these experiments demonstrate the robustness of our
approach in restoring the true albedo of objects, while mitigating the
influence of lighting and medium effects. Furthermore, we demonstrate our
approach can be readily extended to other scenarios, including in-air imaging
with artificial illumination or other similar cases
Self-Supervised Monocular Depth Underwater
Depth estimation is critical for any robotic system. In the past years
estimation of depth from monocular images have shown great improvement,
however, in the underwater environment results are still lagging behind due to
appearance changes caused by the medium. So far little effort has been invested
on overcoming this. Moreover, underwater, there are more limitations for using
high resolution depth sensors, this makes generating ground truth for learning
methods another enormous obstacle. So far unsupervised methods that tried to
solve this have achieved very limited success as they relied on domain transfer
from dataset in air. We suggest training using subsequent frames
self-supervised by a reprojection loss, as was demonstrated successfully above
water. We suggest several additions to the self-supervised framework to cope
with the underwater environment and achieve state-of-the-art results on a
challenging forward-looking underwater dataset
Frequency Compensated Diffusion Model for Real-scene Dehazing
Due to distribution shift, deep learning based methods for image dehazing
suffer from performance degradation when applied to real-world hazy images. In
this paper, we consider a dehazing framework based on conditional diffusion
models for improved generalization to real haze. First, we find that optimizing
the training objective of diffusion models, i.e., Gaussian noise vectors, is
non-trivial. The spectral bias of deep networks hinders the higher frequency
modes in Gaussian vectors from being learned and hence impairs the
reconstruction of image details. To tackle this issue, we design a network
unit, named Frequency Compensation block (FCB), with a bank of filters that
jointly emphasize the mid-to-high frequencies of an input signal. We
demonstrate that diffusion models with FCB achieve significant gains in both
perceptual and distortion metrics. Second, to further boost the generalization
performance, we propose a novel data synthesis pipeline, HazeAug, to augment
haze in terms of degree and diversity. Within the framework, a solid baseline
for blind dehazing is set up where models are trained on synthetic hazy-clean
pairs, and directly generalize to real data. Extensive evaluations show that
the proposed dehazing diffusion model significantly outperforms
state-of-the-art methods on real-world images.Comment: 16 page
Visibility Recovery on Images Acquired in Attenuating Media. Application to Underwater, Fog, and Mammographic Imaging
When acquired in attenuating media, digital images often suffer from a
particularly complex degradation that reduces their visual quality, hindering
their suitability for further computational applications, or simply
decreasing the visual pleasantness for the user. In these cases, mathematical
image processing reveals itself as an ideal tool to recover some
of the information lost during the degradation process. In this dissertation,
we deal with three of such practical scenarios in which this problematic
is specially relevant, namely, underwater image enhancement, fog
removal and mammographic image processing. In the case of digital mammograms,
X-ray beams traverse human tissue, and electronic detectors
capture them as they reach the other side. However, the superposition
on a bidimensional image of three-dimensional structures produces lowcontrasted
images in which structures of interest suffer from a diminished
visibility, obstructing diagnosis tasks. Regarding fog removal, the loss
of contrast is produced by the atmospheric conditions, and white colour
takes over the scene uniformly as distance increases, also reducing visibility.
For underwater images, there is an added difficulty, since colour is not
lost uniformly; instead, red colours decay the fastest, and green and blue
colours typically dominate the acquired images. To address all these challenges,
in this dissertation we develop new methodologies that rely on: a)
physical models of the observed degradation, and b) the calculus of variations.
Equipped with this powerful machinery, we design novel theoretical
and computational tools, including image-dependent functional energies
that capture the particularities of each degradation model. These energies
are composed of different integral terms that are simultaneously
minimized by means of efficient numerical schemes, producing a clean,
visually-pleasant and useful output image, with better contrast and increased
visibility. In every considered application, we provide comprehensive
qualitative (visual) and quantitative experimental results to validate
our methods, confirming that the developed techniques outperform other
existing approaches in the literature
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