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A new preprint is available in IPOL: <a moz-do-not-send="true"
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href="http://www.ipol.im/pub/pre/82/">http://www.ipol.im/pub/pre/82/</a><br>
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Analysis and Extension of the Ponomarenko et al Method, Estimating
a Noise Curve from a Single Image<br>
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Miguel Colom, Antoni Buades<br>
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Abstract<br>
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In the article "An Automatic Approach to Lossy Compression of
AVIRIS Images" N.N. Ponomarenko et al. propose a new method to
specifically compress AVIRIS images. As part of the compression
algorithm, a noise estimation is performed with a proposed new
algorithm based on the computation of the variance of overlapping
8x8 blocks. The noise is estimated on the high-frequency
orthonormal DCT-II coefficients of the blocks. To avoid the effect
of edges and textures, the blocks are sorted according to their
energy measured on a set of low-frequency coefficients. The final
noise estimation is obtained by computing the median of the
variances measured on the high-frequency part of the spectrum of
the blocks using only those whose energy (measured on the
low-frequencies) is low. A small percentile of the total set of
blocks (typically the 0.5%) is used to select those blocks with
the lower energy at the low-frequencies. Although the method
measures uniform Gaussian noise, it can be easily adapted to deal
with signal-dependent noise, which is realistic with the Poisson
noise model obtained by a CCD device in a digital camera.<br>
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