77,439 research outputs found
The Marr Conjecture and Uniqueness of Wavelet Transforms
The inverse question of identifying a function from the nodes (zeroes) of its
wavelet transform arises in a number of fields. These include whether the nodes
of a heat or hypoelliptic equation solution determine its initial conditions,
and in mathematical vision theory the Marr conjecture, on whether an image is
mathematically determined by its edge information. We prove a general version
of this conjecture by reducing it to the moment problem, using a basis dual to
the Taylor monomial basis on .Comment: 52 pages, 4 figure
Contour Detection from Deep Patch-level Boundary Prediction
In this paper, we present a novel approach for contour detection with
Convolutional Neural Networks. A multi-scale CNN learning framework is designed
to automatically learn the most relevant features for contour patch detection.
Our method uses patch-level measurements to create contour maps with
overlapping patches. We show the proposed CNN is able to to detect large-scale
contours in an image efficienly. We further propose a guided filtering method
to refine the contour maps produced from large-scale contours. Experimental
results on the major contour benchmark databases demonstrate the effectiveness
of the proposed technique. We show our method can achieve good detection of
both fine-scale and large-scale contours.Comment: IEEE International Conference on Signal and Image Processing 201
Reconstructive Sparse Code Transfer for Contour Detection and Semantic Labeling
We frame the task of predicting a semantic labeling as a sparse
reconstruction procedure that applies a target-specific learned transfer
function to a generic deep sparse code representation of an image. This
strategy partitions training into two distinct stages. First, in an
unsupervised manner, we learn a set of generic dictionaries optimized for
sparse coding of image patches. We train a multilayer representation via
recursive sparse dictionary learning on pooled codes output by earlier layers.
Second, we encode all training images with the generic dictionaries and learn a
transfer function that optimizes reconstruction of patches extracted from
annotated ground-truth given the sparse codes of their corresponding image
patches. At test time, we encode a novel image using the generic dictionaries
and then reconstruct using the transfer function. The output reconstruction is
a semantic labeling of the test image.
Applying this strategy to the task of contour detection, we demonstrate
performance competitive with state-of-the-art systems. Unlike almost all prior
work, our approach obviates the need for any form of hand-designed features or
filters. To illustrate general applicability, we also show initial results on
semantic part labeling of human faces.
The effectiveness of our approach opens new avenues for research on deep
sparse representations. Our classifiers utilize this representation in a novel
manner. Rather than acting on nodes in the deepest layer, they attach to nodes
along a slice through multiple layers of the network in order to make
predictions about local patches. Our flexible combination of a generatively
learned sparse representation with discriminatively trained transfer
classifiers extends the notion of sparse reconstruction to encompass arbitrary
semantic labeling tasks.Comment: to appear in Asian Conference on Computer Vision (ACCV), 201
A Case for Renewed Activity in the Giant Radio Galaxy J0116-473
We present ATCA radio observations of the giant radio galaxy J0116-473 at 12
and 22 cm wavelengths in total intensity and polarization. The images clearly
reveal a bright inner-double structure within more extended edge-brightened
lobe emission. The lack of hotspots at the ends of the outer lobes, the strong
core and the inner-double structure with its edge-brightened morphology lead us
to suggest that this giant radio galaxy is undergoing a renewed nuclear
activity: J0116-473 appears to be a striking example of a radio galaxy where a
young double source is evolving within older lobe material. We also report the
detection of a Mpc-long linear feature which is oriented perpendicular to the
radio axis and has a high fractional polarization.Comment: 25 pages, 10 figures, appeared in 2002 ApJ, 565, 25
Boundary, Brightness, and Depth Interactions During Preattentive Representation and Attentive Recognition of Figure and Ground
This article applies a recent theory of 3-D biological vision, called FACADE Theory, to explain several percepts which Kanizsa pioneered. These include 3-D pop-out of an occluding form in front of an occluded form, leading to completion and recognition of the occluded form; 3-D transparent and opaque percepts of Kanizsa squares, with and without Varin wedges; and interactions between percepts of illusory contours, brightness, and depth in response to 2-D Kanizsa images. These explanations clarify how a partially occluded object representation can be completed for purposes of object recognition, without the completed part of the representation necessarily being seen. The theory traces these percepts to neural mechanisms that compensate for measurement uncertainty and complementarity at individual cortical processing stages by using parallel and hierarchical interactions among several cortical processing stages. These interactions are modelled by a Boundary Contour System (BCS) that generates emergent boundary segmentations and a complementary Feature Contour System (FCS) that fills-in surface representations of brightness, color, and depth. The BCS and FCS interact reciprocally with an Object Recognition System (ORS) that binds BCS boundary and FCS surface representations into attentive object representations. The BCS models the parvocellular LGN→Interblob→Interstripe→V4 cortical processing stream, the FCS models the parvocellular LGN→Blob→Thin Stripe→V4 cortical processing stream, and the ORS models inferotemporal cortex.Air Force Office of Scientific Research (F49620-92-J-0499); Defense Advanced Research Projects Agency (N00014-92-J-4015); Office of Naval Research (N00014-91-J-4100
Ordered magnetic fields around radio galaxies: evidence for interaction with the environment
We present detailed imaging of Faraday rotation and depolarization for the
radio galaxies 0206+35, 3C 270, 3C 353 and M 84, based on Very Large Array
observations at multiple frequencies in the range 1365 to 8440 MHz. This work
suggests a more complex picture of the magneto-ionic environments of radio
galaxies than was apparent from earlier work. All of the sources show
spectacular banded rotation measure (RM) structures with contours of constant
RM perpendicular to the major axes of their radio lobes. We give a
comprehensive description of the banded RM phenomenon and present an initial
attempt to interpret it as a consequence of interactions between the sources
and their surroundings. We show that the material responsible for the Faraday
rotation is in front of the radio emission and that the bands are likely to be
caused by magnetized plasma which has been compressed by the expanding radio
lobes. A two-dimensional magnetic structure in which the field lines are a
family of ellipses draped around the leading edge of the lobe can produce RM
bands in the correct orientation for any source orientation. We also report the
first detections of rims of high depolarization at the edges of the inner radio
lobes of M 84 and 3C 270. These are spatially coincident with shells of
enhanced X-ray surface brightness, in which both the field strength and the
thermal gas density are likely to be increased by compression.Comment: 21 pages, 15 figures, accepted for publication in MNRAS. Full
resolution paper available at http://www.ira.inaf.it/~guidetti/bands/
Subjects: Astrophysics (astro-ph
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