###

## Stripe LSLCD optimization

The block diagram for the demosaicking of the stripe structure is the
following:

By tracing the demosaicking steps described in the figure and omitting any
multiplications involving a constant operand, the number of multiplications S
required to demosaic one image pixel is:

Where both the real and the imaginary parts of the h_{2} filter have
a M_{1}xM_{2} order.

Because of the diagonal symmetry we noticed in the power spectrum we only
took into consideration the square filters when performing the greedy
algorithm. In this case:

The number of multiplications used by the algorithm can be reduced if we
take into consideration filter properties. If we make use of the filter
quadrantal symmetry, the number of multiplications required to demosaic one
pixel is:

If we use separable filters, then the number of computations required for
demosaicking becomes:

### Optimization results

The filter design training set and the demosaicking test set of color images
consisted of subsets from the 24 Kodak photo-sampler images of size 512x768
that are widely used in the demosaicking literature. The figures below show the
changes to objective demosaicking quality, measured by CMSE as a function of
computational complexity, measured by the number of multiplications for the
general structure without imposing quadrantal symmetry.

The experiment results confirm the tradeoff relationship between
demosaicking quality and speed. The plot line indicates that a 5x5 filter size
represents a good filter order when demosaicking a Stripe CFA image.