Unused functions.
I keep them around for reference, for whoever wants to work on
improving the encoder.
There are still some warnings. Clang is just crazy.
No need to write out alpha in a RGBA color when only
the RGB values are used by the distance op.
Also, add a comment on the byte order. Maybe I'm wrong
but I believe the operations are fine wrt. byte order :)
There is still some C99 code in the file in the form of
for (int k = 0; ...)
If there's a strong requirement not to use this form, I'll
change it, otherwise I find this specific code style more
readable (k is local to this iteration).
This patch and the previous one even give a ~10% speedup
on the encoding time. Sweet :)
So I guess always compiling with debug flags and no
optimizations isn't the best idea as some really bad warnings
can be hidden. Thanks raster for the notice.
And this completes the first version of this ETC2 encoder.
It's pretty slow and not exhaustive.
Color selection for T and H modes could probably be optimized
for both performance and quality. As for the planar mode, there
is no selection to speak of, as we just take the values of the
pixels directly (no scan, very fast)
On a sample image with lots of blue, white and noisy gradients,
T+H+Planar mode boost the PNSR from 41.22dB to 42.01dB.
Without planar mode, the PSNR was 41.94dB.
@feature
In this mode, two colors are encoded in RGB444, a multiplier and
distance (index) are selected. Two extra colors are extrapolated
from the main base color. As in ETC1 we have 4 base colors to paint
our block.
@feature
Implement Alpha encoding, brute force way, but doesn't scan
all possibilities either (only based on average alpha).
RGB encoding is still entirely left to the rg-etc1 encoder.
T, H and Planar mode will come in the next commits.
@feature: Implement an ETC2 encoder from scratch for RGB8 and RGBA8
Jean-Philippe Andre
Mike Blumenkrantz
Jean-Philippe ANDRE