220 research outputs found
Fast Mojette Transform for Discrete Tomography
A new algorithm for reconstructing a two dimensional object from a set of one
dimensional projected views is presented that is both computationally exact and
experimentally practical. The algorithm has a computational complexity of O(n
log2 n) with n = N^2 for an NxN image, is robust in the presence of noise and
produces no artefacts in the reconstruction process, as is the case with
conventional tomographic methods. The reconstruction process is approximation
free because the object is assumed to be discrete and utilizes fully discrete
Radon transforms. Noise in the projection data can be suppressed further by
introducing redundancy in the reconstruction. The number of projections
required for exact reconstruction and the response to noise can be controlled
without comprising the digital nature of the algorithm. The digital projections
are those of the Mojette Transform, a form of discrete linogram. A simple
analytical mapping is developed that compacts these projections exactly into
symmetric periodic slices within the Discrete Fourier Transform. A new digital
angle set is constructed that allows the periodic slices to completely fill all
of the objects Discrete Fourier space. Techniques are proposed to acquire these
digital projections experimentally to enable fast and robust two dimensional
reconstructions.Comment: 22 pages, 13 figures, Submitted to Elsevier Signal Processin
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A Fast and Accurate Iris Localization Technique for Healthcare Security System
yesIn the health care systems, a high security level is
required to protect extremely sensitive patient records. The goal
is to provide a secure access to the right records at the right time
with high patient privacy. As the most accurate biometric system,
the iris recognition can play a significant role in healthcare
applications for accurate patient identification. In this paper, the
corner stone towards building a fast and robust iris recognition
system for healthcare applications is addressed, which is known
as iris localization. Iris localization is an essential step for
efficient iris recognition systems. The presence of extraneous
features such as eyelashes, eyelids, pupil and reflection spots
make the correct iris localization challenging. In this paper, an
efficient and automatic method is presented for the inner and
outer iris boundary localization. The inner pupil boundary is
detected after eliminating specular reflections using a
combination of thresholding and morphological operations.
Then, the outer iris boundary is detected using the modified
Circular Hough transform. An efficient preprocessing procedure
is proposed to enhance the iris boundary by applying 2D
Gaussian filter and Histogram equalization processes. In
addition, the pupil’s parameters (e.g. radius and center
coordinates) are employed to reduce the search time of the
Hough transform by discarding the unnecessary edge points
within the iris region. Finally, a robust and fast eyelids detection
algorithm is developed which employs an anisotropic diffusion
filter with Radon transform to fit the upper and lower eyelids
boundaries. The performance of the proposed method is tested
on two databases: CASIA Version 1.0 and SDUMLA-HMT iris
database. The Experimental results demonstrate the efficiency of
the proposed method. Moreover, a comparative study with other
established methods is also carried out
Off-line Arabic Handwriting Recognition System Using Fast Wavelet Transform
In this research, off-line handwriting recognition system for Arabic alphabet is
introduced. The system contains three main stages: preprocessing, segmentation and
recognition stage. In the preprocessing stage, Radon transform was used in the design
of algorithms for page, line and word skew correction as well as for word slant
correction. In the segmentation stage, Hough transform approach was used for line
extraction. For line to words and word to characters segmentation, a statistical method
using mathematic representation of the lines and words binary image was used.
Unlike most of current handwriting recognition system, our system simulates the
human mechanism for image recognition, where images are encoded and saved in
memory as groups according to their similarity to each other. Characters are
decomposed into a coefficient vectors, using fast wavelet transform, then, vectors,
that represent a character in different possible shapes, are saved as groups with one
representative for each group. The recognition is achieved by comparing a vector of
the character to be recognized with group representatives.
Experiments showed that the proposed system is able to achieve the recognition task
with 90.26% of accuracy. The system needs only 3.41 seconds a most to recognize a
single character in a text of 15 lines where each line has 10 words on average
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