Image Processing Reference
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Image coder based on contrast band-pass filtering
Jaime Moreno 1 , 2 ; Oswaldo Morales 1 ; Ricardo Tejeida 1
1 Superior School of Mechanical and Electrical Engineers, National Polytechnic
Institute of Mexico, IPN Avenue, Lindavista, Mexico City, Mexico
2 Signal, Image and Communications Department, University of Poitiers, Poitiers, France
Noise is fatal to image compression performance because it can be both annoying for the observer and
consumes excessive bandwidth when the imagery is transmited. Some noise, in addition to some nu-
merical redundancy, is removed during the quantization process, but in some circumstances the re-
moved information is easily perceived by the observer, leading to annoying visual artifacts. Perceptual
quantization reduces unperceivable details and thus improves both visual impression and transmission
properties. In this work, we apply perceptual criteria in order to define a perceptual forward and inverse
quantizer. It is based on the CBPF, a low-level computational model that reproduces color perception in
the Human Visual System. Our approach consists in performing a local quantization of wavelet trans-
form coefficients using some of the human visual system behavior properties. It is performed apply-
ing a local weight for every coefficient. The CBPF allows recovering these weights from the quantized
data, which avoids the storing and transmission of these weights. We apply this perceptual quantizer
to the H i -SET coder. The comparison between JPEG2000 coder and the combination of H i -SET with the
proposed perceptual quantizer (XSET) is shown. The later produces images with lower PSNR than the
former, but they have the same or even beter visual quality when measured with well-known image
quality metrics such as MSSIM, UQI, or VIF, for instance. Hence, XSET obtain more compressed (i.e.,
lower bit-rate) images at the same perceptual image quality than JPEG2000.
Contrast sensitivity function
Human visual system
Wavelet transform
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