MAX_LEN -> max_len
This was sub-optimal at the end of the picture, when there's
less than MAX_LEN bytes left to match.
Change-Id: I5ebe1fca4e7c112dcd34748a082d1c97f95eb099
.. where only 2 filtering modes are potentially
tried, instead of all of them. This is fast than the exhaustive 'best'
mode, and not much worse.
Options for cwebp are:
-alpha_filter none
-alpha_filter fast (<- default)
-alpha_filter best (<- slow)
Change-Id: I8cb90ee11b8f981811e013ea4ad5bf72ba3ea7d4
Add predictive filtering option for Alpha plane.
Valid range for filter option is [0, 5] corresponding to prediction
methods none, horizontal, vertical, gradient & paeth filter.
The prediction method 5 will try all the prediction methods (0 to 4)
and pick the prediction method that gives best compression.
Change-Id: I9244d4a9c5017501a9696c7cec5045f04c16d49b
Add code for Alpha encoding & decoding. The alpha compression is done
via backward reference counts encoded with Arithmetic encoder (TCoder).
Also provided is lossy Alpha pre-processing option via level-quantizations
using kNN heuristic.
Change-Id: Ib6b13530c1a4ab6493edcb586ad29fe242bc1766
