8,013 research outputs found
Invertible Rescaling Network and Its Extensions
Image rescaling is a commonly used bidirectional operation, which first
downscales high-resolution images to fit various display screens or to be
storage- and bandwidth-friendly, and afterward upscales the corresponding
low-resolution images to recover the original resolution or the details in the
zoom-in images. However, the non-injective downscaling mapping discards
high-frequency contents, leading to the ill-posed problem for the inverse
restoration task. This can be abstracted as a general image
degradation-restoration problem with information loss. In this work, we propose
a novel invertible framework to handle this general problem, which models the
bidirectional degradation and restoration from a new perspective, i.e.
invertible bijective transformation. The invertibility enables the framework to
model the information loss of pre-degradation in the form of distribution,
which could mitigate the ill-posed problem during post-restoration. To be
specific, we develop invertible models to generate valid degraded images and
meanwhile transform the distribution of lost contents to the fixed distribution
of a latent variable during the forward degradation. Then restoration is made
tractable by applying the inverse transformation on the generated degraded
image together with a randomly-drawn latent variable. We start from image
rescaling and instantiate the model as Invertible Rescaling Network (IRN),
which can be easily extended to the similar decolorization-colorization task.
We further propose to combine the invertible framework with existing
degradation methods such as image compression for wider applications.
Experimental results demonstrate the significant improvement of our model over
existing methods in terms of both quantitative and qualitative evaluations of
upscaling and colorizing reconstruction from downscaled and decolorized images,
and rate-distortion of image compression.Comment: Accepted by IJC
Faithful extreme rescaling via generative prior reciprocated invertible representations
This paper presents a Generative prior ReciprocAted Invertible rescaling Network (GRAIN) for generating faithful high-resolution (HR) images from low-resolution (LR) invertible images with an extreme upscaling factor (64). Previous researches have leveraged the prior knowledge of a pretrained GAN model to generate high-quality upscaling results. However, they fail to produce pixel-accurate results due to the highly ambiguous extreme mapping process. We remedy this problem by introducing a reciprocated invertible image rescaling process, in which high-resolution information can be delicately embedded into an invertible low-resolution image and generative prior for a faithful HR reconstruction. In particular, the invertible LR features not only carry significant HR semantics, but also are trained to predict scale-specific latent codes, yielding a preferable utilization of generative features. On the other hand, the enhanced generative prior is re-injected to the rescaling process, compensating the lost details of the invertible rescaling. Our reciprocal mechanism perfectly integrates the advantages of invertible encoding and generative prior, leading to the first feasible extreme rescaling solution. Extensive experiments demonstrate superior performance against state-of-the-art upscaling methods. Code is available at https://github.com/cszzx/GRAIN
Self-Asymmetric Invertible Network for Compression-Aware Image Rescaling
High-resolution (HR) images are usually downscaled to low-resolution (LR)
ones for better display and afterward upscaled back to the original size to
recover details. Recent work in image rescaling formulates downscaling and
upscaling as a unified task and learns a bijective mapping between HR and LR
via invertible networks. However, in real-world applications (e.g., social
media), most images are compressed for transmission. Lossy compression will
lead to irreversible information loss on LR images, hence damaging the inverse
upscaling procedure and degrading the reconstruction accuracy. In this paper,
we propose the Self-Asymmetric Invertible Network (SAIN) for compression-aware
image rescaling. To tackle the distribution shift, we first develop an
end-to-end asymmetric framework with two separate bijective mappings for
high-quality and compressed LR images, respectively. Then, based on empirical
analysis of this framework, we model the distribution of the lost information
(including downscaling and compression) using isotropic Gaussian mixtures and
propose the Enhanced Invertible Block to derive high-quality/compressed LR
images in one forward pass. Besides, we design a set of losses to regularize
the learned LR images and enhance the invertibility. Extensive experiments
demonstrate the consistent improvements of SAIN across various image rescaling
datasets in terms of both quantitative and qualitative evaluation under
standard image compression formats (i.e., JPEG and WebP).Comment: Accepted by AAAI 2023. Code is available at
https://github.com/yang-jin-hai/SAI
Invertible Mosaic Image Hiding Network for Very Large Capacity Image Steganography
The existing image steganography methods either sequentially conceal secret
images or conceal a concatenation of multiple images. In such ways, the
interference of information among multiple images will become increasingly
severe when the number of secret images becomes larger, thus restrict the
development of very large capacity image steganography. In this paper, we
propose an Invertible Mosaic Image Hiding Network (InvMIHNet) which realizes
very large capacity image steganography with high quality by concealing a
single mosaic secret image. InvMIHNet consists of an Invertible Image Rescaling
(IIR) module and an Invertible Image Hiding (IIH) module. The IIR module works
for downscaling the single mosaic secret image form by spatially splicing the
multiple secret images, and the IIH module then conceal this mosaic image under
the cover image. The proposed InvMIHNet successfully conceal and reveal up to
16 secret images with a small number of parameters and memory consumption.
Extensive experiments on ImageNet-1K, COCO and DIV2K show InvMIHNet outperforms
state-of-the-art methods in terms of both the imperceptibility of stego image
and recover accuracy of secret image
The moduli space of matroids
In the first part of the paper, we clarify the connections between several
algebraic objects appearing in matroid theory: both partial fields and
hyperfields are fuzzy rings, fuzzy rings are tracts, and these relations are
compatible with the respective matroid theories. Moreover, fuzzy rings are
ordered blueprints and lie in the intersection of tracts with ordered
blueprints; we call the objects of this intersection pastures.
In the second part, we construct moduli spaces for matroids over pastures. We
show that, for any non-empty finite set , the functor taking a pasture
to the set of isomorphism classes of rank- -matroids on is
representable by an ordered blue scheme , the moduli space of
rank- matroids on .
In the third part, we draw conclusions on matroid theory. A classical
rank- matroid on corresponds to a -valued point of
where is the Krasner hyperfield. Such a point defines a
residue pasture , which we call the universal pasture of . We show that
for every pasture , morphisms are canonically in bijection with
-matroid structures on .
An analogous weak universal pasture classifies weak -matroid
structures on . The unit group of can be canonically identified with
the Tutte group of . We call the sub-pasture of generated by
``cross-ratios' the foundation of ,. It parametrizes rescaling classes of
weak -matroid structures on , and its unit group is coincides with the
inner Tutte group of . We show that a matroid is regular if and only if
its foundation is the regular partial field, and a non-regular matroid is
binary if and only if its foundation is the field with two elements. This
yields a new proof of the fact that a matroid is regular if and only if it is
both binary and orientable.Comment: 83 page
Blind Normalization of Speech From Different Channels
We show how to construct a channel-independent representation of speech that
has propagated through a noisy reverberant channel. This is done by blindly
rescaling the cepstral time series by a non-linear function, with the form of
this scale function being determined by previously encountered cepstra from
that channel. The rescaled form of the time series is an invariant property of
it in the following sense: it is unaffected if the time series is transformed
by any time-independent invertible distortion. Because a linear channel with
stationary noise and impulse response transforms cepstra in this way, the new
technique can be used to remove the channel dependence of a cepstral time
series. In experiments, the method achieved greater channel-independence than
cepstral mean normalization, and it was comparable to the combination of
cepstral mean normalization and spectral subtraction, despite the fact that no
measurements of channel noise or reverberations were required (unlike spectral
subtraction).Comment: 25 pages, 7 figure
Quantum Lie algebras; their existence, uniqueness and -antisymmetry
Quantum Lie algebras are generalizations of Lie algebras which have the
quantum parameter h built into their structure. They have been defined
concretely as certain submodules of the quantized enveloping algebras. On them
the quantum Lie bracket is given by the quantum adjoint action.
Here we define for any finite-dimensional simple complex Lie algebra g an
abstract quantum Lie algebra g_h independent of any concrete realization. Its
h-dependent structure constants are given in terms of inverse quantum
Clebsch-Gordan coefficients. We then show that all concrete quantum Lie
algebras are isomorphic to an abstract quantum Lie algebra g_h.
In this way we prove two important properties of quantum Lie algebras: 1) all
quantum Lie algebras associated to the same g are isomorphic, 2) the quantum
Lie bracket of any quantum Lie algebra is -antisymmetric. We also describe a
construction of quantum Lie algebras which establishes their existence.Comment: 18 pages, amslatex. Files also available from
http://www.mth.kcl.ac.uk/~delius/q-lie/qlie_biblio/qlieuniq.htm
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