21,461 research outputs found
Visual Chunking: A List Prediction Framework for Region-Based Object Detection
We consider detecting objects in an image by iteratively selecting from a set
of arbitrarily shaped candidate regions. Our generic approach, which we term
visual chunking, reasons about the locations of multiple object instances in an
image while expressively describing object boundaries. We design an
optimization criterion for measuring the performance of a list of such
detections as a natural extension to a common per-instance metric. We present
an efficient algorithm with provable performance for building a high-quality
list of detections from any candidate set of region-based proposals. We also
develop a simple class-specific algorithm to generate a candidate region
instance in near-linear time in the number of low-level superpixels that
outperforms other region generating methods. In order to make predictions on
novel images at testing time without access to ground truth, we develop
learning approaches to emulate these algorithms' behaviors. We demonstrate that
our new approach outperforms sophisticated baselines on benchmark datasets.Comment: to appear at ICRA 201
T-PHOT: A new code for PSF-matched, prior-based, multiwavelength extragalactic deconfusion photometry
We present T-PHOT, a publicly available software aimed at extracting accurate
photometry from low-resolution images of deep extragalactic fields, where the
blending of sources can be a serious problem for the accurate and unbiased
measurement of fluxes and colours. T-PHOT has been developed within the
ASTRODEEP project and it can be considered as the next generation to TFIT,
providing significant improvements above it and other similar codes. T-PHOT
gathers data from a high-resolution image of a region of the sky, and uses it
to obtain priors for the photometric analysis of a lower resolution image of
the same field. It can handle different types of datasets as input priors: i) a
list of objects that will be used to obtain cutouts from the real
high-resolution image; ii) a set of analytical models; iii) a list of
unresolved, point-like sources, useful e.g. for far-infrared wavelength
domains. We show that T-PHOT yields accurate estimations of fluxes within the
intrinsic uncertainties of the method, when systematic errors are taken into
account (which can be done thanks to a flagging code given in the output).
T-PHOT is many times faster than similar codes like TFIT and CONVPHOT (up to
hundreds, depending on the problem and the method adopted), whilst at the same
time being more robust and more versatile. This makes it an optimal choice for
the analysis of large datasets. In addition we show how the use of different
settings and methods significantly enhances the performance. Given its
versatility and robustness, T-PHOT can be considered the preferred choice for
combined photometric analysis of current and forthcoming extragalactic optical
to far-infrared imaging surveys. [abridged]Comment: 23 pages, 20 figures, 2 table
Accelerated hardware video object segmentation: From foreground detection to connected components labelling
This is the preprint version of the Article - Copyright @ 2010 ElsevierThis paper demonstrates the use of a single-chip FPGA for the segmentation of moving objects in a video sequence. The system maintains highly accurate background models, and integrates the detection of foreground pixels with the labelling of objects using a connected components algorithm. The background models are based on 24-bit RGB values and 8-bit gray scale intensity values. A multimodal background differencing algorithm is presented, using a single FPGA chip and four blocks of RAM. The real-time connected component labelling algorithm, also designed for FPGA implementation, run-length encodes the output of the background subtraction, and performs connected component analysis on this representation. The run-length encoding, together with other parts of the algorithm, is performed in parallel; sequential operations are minimized as the number of run-lengths are typically less than the number of pixels. The two algorithms are pipelined together for maximum efficiency
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