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WSQ compression and decompression
The Agora WSQ - Wavelet Scalar
Quantization - is a set of routines that implements the
"WSQ Gray-scale Fingerprint Image Compression
Specification", specified by the Federal Bureau of
Investigation (FBI) in 1993. The Agora WSQ
software has achieved the FBI's certification of
compliance to the standard. This means that
an image compressed with Agora may be decompressed and
viewed with another vendor's standard compliant
software, and vice versa. The Agora WSQ technology
ensures interoperability, and this benefits the
customer.
In simple terms, WSQ is a image
compression technique to reduce the size of a
fingerprint image, sacrificing its quality as little as
possible. It was designed
specificallytargeting fingerprint images,
using their spectral characteristics to optimize the
compression process. The process is "lossy", meaning
that the reconstructed image isn't equal to the
original; some information being lost. The WSQ algorithm
was specially designed to minimize the loss of
information, so that the reconstructed image be as close
as possible to the original; the differences frequently
being imperceptible. The use of other compression
algorithms such as JPG to compress fingerprints results
in higher losses affecting the features. This
reduces the accuracy of identification. One
reason to use WSQ is to maintain the image
quality and therefore the accuracy of identification.
The other one other one is interoperablity
With Agora the size reduction factor is
adjustable, typically being set to the FBI recommended
reduction of fifteen times (15x). This means that a
512x512 image, originally occupying 256 KB, can be
reduced to approximately 17 KB. In large data
bases, the saved space is enormous. Higher
compression ratios may be used, but it is not
recommended because the image quality starts to
diminish.
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