Image Processing Reference

In-Depth Information

(4)

This scale defines the shape dimension in the direction
θ
k
. The ICI rule is applied in all eight

directions and thereby a neighborhood

for the pixel position
x
is found. This neighbor-

hood can now be used for denoising.

3.3 Shape-adaptive DCT and Denoising via Hard Thresholding

The shape of the neighborhood is found for each pixel. Now the SA-DCT must be applied on

the Bayer data to perform the denoising. Therefore the Bayer data is separated into the four

sub-channels,
R
,
G
1
,
G
2
, and
B
, which each contain fourth of the total number of pixels.

is obtained by thresholding in the SA-DCT domain with the threshold parameter
t
x
set to

(5)

The constant
k
thr
regulates the denoising strength. The global estimate is given by a weighted

average of the local estimates.

(6)

The weights
w
x
are calculated based on the size of the neighborhood

and the noise variance

σ
2
. A smaller neighborhood gets higher weights, thus fine details are preserved. is the

number of non-zero coefficients after thresholding, thus sparse solutions are preferred over

non-sparse solutions.

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