147,832 research outputs found
Resolution-Independent Meshes of Superpixels
The over-segmentation into superpixels is an important preprocessing step to
smartly compress the input size and speed up higher level tasks. A superpixel
was traditionally considered as a small cluster of square-based pixels that
have similar color intensities and are closely located to each other. In this
discrete model the boundaries of superpixels often have irregular zigzags
consisting of horizontal or vertical edges from a given pixel grid. However
digital images represent a continuous world, hence the following continuous
model in the resolution-independent formulation can be more suitable for the
reconstruction problem.
Instead of uniting squares in a grid, a resolution-independent superpixel is
defined as a polygon that has straight edges with any possible slope at
subpixel resolution. The harder continuous version of the over-segmentation
problem is to split an image into polygons and find a best (say, constant)
color of each polygon so that the resulting colored mesh well approximates the
given image. Such a mesh of polygons can be rendered at any higher resolution
with all edges kept straight.
We propose a fast conversion of any traditional superpixels into polygons and
guarantees that their straight edges do not intersect. The meshes based on the
superpixels SEEDS (Superpixels Extracted via Energy-Driven Sampling) and SLIC
(Simple Linear Iterative Clustering) are compared with past meshes based on the
Line Segment Detector. The experiments on the Berkeley Segmentation Database
confirm that the new superpixels have more compact shapes than pixel-based
superpixels
YODA: You Only Diffuse Areas. An Area-Masked Diffusion Approach For Image Super-Resolution
This work introduces "You Only Diffuse Areas" (YODA), a novel method for
partial diffusion in Single-Image Super-Resolution (SISR). The core idea is to
utilize diffusion selectively on spatial regions based on attention maps
derived from the low-resolution image and the current time step in the
diffusion process. This time-dependent targeting enables a more effective
conversion to high-resolution outputs by focusing on areas that benefit the
most from the iterative refinement process, i.e., detail-rich objects. We
empirically validate YODA by extending leading diffusion-based SISR methods SR3
and SRDiff. Our experiments demonstrate new state-of-the-art performance gains
in face and general SR across PSNR, SSIM, and LPIPS metrics. A notable finding
is YODA's stabilization effect on training by reducing color shifts, especially
when induced by small batch sizes, potentially contributing to
resource-constrained scenarios. The proposed spatial and temporal adaptive
diffusion mechanism opens promising research directions, including developing
enhanced attention map extraction techniques and optimizing inference latency
based on sparser diffusion.Comment: Brian B. Moser and Stanislav Frolov contributed equall
Gradient metasurfaces: a review of fundamentals and applications
In the wake of intense research on metamaterials the two-dimensional
analogue, known as metasurfaces, has attracted progressively increasing
attention in recent years due to the ease of fabrication and smaller insertion
losses, while enabling an unprecedented control over spatial distributions of
transmitted and reflected optical fields. Metasurfaces represent optically thin
planar arrays of resonant subwavelength elements that can be arranged in a
strictly or quasi periodic fashion, or even in an aperiodic manner, depending
on targeted optical wavefronts to be molded with their help. This paper reviews
a broad subclass of metasurfaces, viz. gradient metasurfaces, which are devised
to exhibit spatially varying optical responses resulting in spatially varying
amplitudes, phases and polarizations of scattered fields. Starting with
introducing the concept of gradient metasurfaces, we present classification of
different metasurfaces from the viewpoint of their responses, differentiating
electrical-dipole, geometric, reflective and Huygens' metasurfaces. The
fundamental building blocks essential for the realization of metasurfaces are
then discussed in order to elucidate the underlying physics of various physical
realizations of both plasmonic and purely dielectric metasurfaces. We then
overview the main applications of gradient metasurfaces, including waveplates,
flat lenses, spiral phase plates, broadband absorbers, color printing,
holograms, polarimeters and surface wave couplers. The review is terminated
with a short section on recently developed nonlinear metasurfaces, followed by
the outlook presenting our view on possible future developments and
perspectives for future applications.Comment: Accepted for publication in Reports on Progress in Physic
Controlled Synthesis of Organic/Inorganic van der Waals Solid for Tunable Light-matter Interactions
Van der Waals (vdW) solids, as a new type of artificial materials that
consist of alternating layers bonded by weak interactions, have shed light on
fascinating optoelectronic device concepts. As a result, a large variety of vdW
devices have been engineered via layer-by-layer stacking of two-dimensional
materials, although shadowed by the difficulties of fabrication. Alternatively,
direct growth of vdW solids has proven as a scalable and swift way, highlighted
by the successful synthesis of graphene/h-BN and transition metal
dichalcogenides (TMDs) vertical heterostructures from controlled vapor
deposition. Here, we realize high-quality organic and inorganic vdW solids,
using methylammonium lead halide (CH3NH3PbI3) as the organic part (organic
perovskite) and 2D inorganic monolayers as counterparts. By stacking on various
2D monolayers, the vdW solids behave dramatically different in light emission.
Our studies demonstrate that h-BN monolayer is a great complement to organic
perovskite for preserving its original optical properties. As a result,
organic/h-BN vdW solid arrays are patterned for red light emitting. This work
paves the way for designing unprecedented vdW solids with great potential for a
wide spectrum of applications in optoelectronics
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