Digital Signal Processing Reference
In-Depth Information
[1,2,3,4,5]. They are excellent but still it is needed to make effort for the
higher efficiency in image coding. The presented method is lossy
compression one and completely compatible with such a traditional coding
method. Using a directional difference on the DWT-approximation we can
get a rough estimate of the DWT-detail in the case that Haar mother wavelet
function is employed. A higher image compression rate is attained if the
above nature is utilized well.
2.
DISCRETE WAVELET TRANSFORM
Discrete wavelet transform (DWT) has an interesting nature for image
compression. DWT is a relatively new transform and many mother wavelet
functions are there. Hence we can choose an appropriate mother function for
the problem under consideration. Here we utilize a Haar function as a mother
wavelet because the resulting DWT coefficients are similar to the difference
image. The DWT is defined as (Transform):
where
is a scaling coefficient as
and
is a wavelet coefficient as
is a scaling function sequence of Doubchies.
is a wavelet function
sequence and has a relation with
as
