improve VP8L signature detection by checking the version bits too

Change-Id: I20bea00b9582d7ea8c7b643616c78f717ce1bdf2
7-8% faster decoding by rewriting GetCoeffs()

Change-Id: Ib7c27e985d3b5222e8fa1f98cec462458caa9541
gif2webp: Different kmin/kmax defaults for lossy and lossless

These were the best values found considering the compression gain and
decoding speed.

Change-Id: Iddae4c5b78c6aa42b1f8a034d1c1b93843071a81
gif2webp: Improved compression for lossy animated WebP

We reduce transparency by turning some transparent pixels into
corresponding RGB values from previous canvas.

This improves compression by about 23%.

Change-Id: I02d70a43a1d0906ac09a7e2dc510be3b2d38f593
Merge "7-8% faster decoding by rewriting GetCoeffs()"
special-case WHT transform when there's only DC

happens surprisingly often at low quality, so we might
as well hard-code a simplified TransformWHT() directly.

Change-Id: Ib7a858ef74e8f334bd59d6512bf5bd3e455c5459
Android.mk: update build flags

- split out release specific flags
- set LOCAL_ARM_MODE to arm

Change-Id: I272855216583d6c8d0a4106e8b3fde46aa59dfa9
Android.mk: add a dwebp target

Change-Id: Ic697660c1a5f7185d2ad00934b314b44870cec00
Merge changes Ic697660c,I27285521

* changes:
  Android.mk: add a dwebp target
  Android.mk: update build flags
small gif2webp fix

the old kmin value was printed instead of the new one.

Change-Id: I0dcf23a29b7ce6bad08013a1980c5ce027b1bfe9
small optimization in segment-smoothing loop

probably not much of a speed difference

Change-Id: I08c41d82c3c2eb5ff9ec9ca9d81af2bb09b362de
Merge "small optimization in segment-smoothing loop"
only print GIF_DISPOSE_WARNING once

Change-Id: Iece235a6ee767cc2e3866bb6c9bb1d56d9a9ffb9
gif2webp: detect and flatten uniformly similar blocks

helps during lossless compression.

10% average saving, but that's mostly on what was previously
'difficult' cases, where the gain is ~30-50% actually.
Non-difficult cases are mostly unchanged.
Tested over ~7k random web gifs.

Change-Id: I09db4560e4ab09105d1cad28e6dbf83842eda8e9
Special-case sparse transform

If the number of non-zero coeffs is <= 3, use a
simplified transform for luma.

Change-Id: I78a1252704228d21720d4bc1221252c84338d9c8
use a macrofunc for setting NzCoeffs bits

(avoids code dup)

Change-Id: I776f065538e562673ca08f3bc43c7167d13254d9
use HINT_GRAPH as image_hint for gif source

quite rarely, it gives a different output
then without the HINT, but that's often for
a smaller size (tested with default -m and -m 6)

Change-Id: I51d221ab61f8e007983325031345728e8d80b241
Merge "only print GIF_DISPOSE_WARNING once"
Merge "use HINT_GRAPH as image_hint for gif source"
Merge "use a macrofunc for setting NzCoeffs bits"