5-10% encoding speedup with faster trellis (-m 6)

mostly by:
- storing a single rd-score instead of cost / distortion separately
- evaluating terminal cost only once
- getting some invariants out of the loops
- more consts behind fewer variables

Change-Id: I79451f3fd1143d6537200fb8b90d0ba252809f8c
Merge "5-10% encoding speedup with faster trellis (-m 6)"
Refactor code for HistogramCombine.

Refactor code for HistogramCombine and optimize the code by calculating
the combined entropy and avoid un-necessary Histogram merges.

This speeds up lossless encoding by 1-2% and almost no impact on compression
density.

Change-Id: Iedfcf4c1f3e88077bc77fc7b8c780c4cd5d6362b
few cosmetics after patch #69079

Change-Id: Ifa758420421b5a05825a593f6b43504887603ee7
Merge "few cosmetics after patch #69079"
~3-4% faster lossless encoding

by re-arranging some code from SkipRepeatedPixel()

Change-Id: I6c1fd7cd9af22cd9be4234217ff67d7b94f44137
Merge "~3-4% faster lossless encoding"
histogram.c: reindent after b33e8a0

b33e8a0 Refactor code for HistogramCombine.

Change-Id: Ia1b4b545c5f4e29cc897339df2b58f18f83c15b3
4-5% faster trellis by removing some unneeded calculations.

(We didn't need the exact value of the max_error properly.
We can work with relative values instead of absolute)

Output is bitwise the same as before.

Change-Id: I67aeaaea5f81bfd9ca8e1158387a5083a2b6c649
add a -z option to cwebp, and WebPConfigLosslessPreset() function

These are presets for lossless coding, similar to zlib.
The shortcut for lossless coding is now, e.g.:
   cwebp -z 5 in.png -o out_lossless.webp

There are 10 possible values for -z parameter:
   0 (fastest, lowest compression)
to 9 (slowest, best compression)

A reasonable tradeoff is -z 6, e.g.
-z 9 can be quite slow, so use with care.

This -z option is just a shortcut for some pre-defined
'-lossless -m xx -q yy' combinations.

Change-Id: I6ae716456456aea065469c916c2d5ca4d6c6cf04
fix cwebp.1 typos after patch #69199

Change-Id: I046a54dbb4210319ddb156f49dd9d13d47b0d035
allow some more stdin/stout I/O

 * allow reading from stdin for dwebp / vwebp
 * allow writing to stdout for gif2webp

by introducing a new function ExUtilReadFromStdin()

Example use: cat in.webp | dwebp -o - -- - > out.png

Note that the '-- -' option must appear *last*
(as per general fashion for '--' option parsing)

Change-Id: I8df0f3a246cc325925d6b6f668ba060f7dd81d68
allow 'cwebp -o -' to emit output to stdout

Change-Id: I423d25898e1ba317ccbf456bb28ce45663a3b3d2
Merge "allow 'cwebp -o -' to emit output to stdout"
Do a binary search to get the optimum cache bits.

This speeds up the lossless encoder by a bit (1-2%), without impacting the
compression density.

Change-Id: Ied6fb38fab58eef9ded078697e0463fe7c560b26
Optimize lossless decoding.

Restructure PredictorInverseTransform & ColorSpaceInverseTransform to remove
one if condition inside the main/critial loop. Also separated TransformColor &
TransformColorInverse into separate functions and avoid one 'if condition'
inside this critical method.

This change speeds up lossless decoding for Lenna image about 5% and 1000 image
corpus by 3-4%.

Change-Id: I4bd390ffa4d3bcf70ca37ef2ff2e81bedbba197d
Optimize and re-structure VP8LGetHistoImageSymbols

Optimize and re-structured VP8LGetHistoImageSymbols method, by using the bin-hash
for merging the Histograms more efficiently, instead of the randomized
heuristic of existing method HistogramCombine.

This change speeds up the Lossless encoding by 40-50% (for method=4 and Q > 50)
with 0.8% penalty in compression density. For lower method, the speed up is 25-30%,
with 0.4% penalty in the compression density.

Change-Id: If61adadb1a041b95def6405aa1fe3b83c3cb25ce
Fix few nits

Add/remove few casts, fixed indentation.

Change-Id: Icd141694201843c04e476f09142ce4be6e502dff
Extend the search space for GetBestGreenRedToBlue

Get back some of the compression gains by extending the search space for
GetBestGreenRedToBlue. Also removed the SkipRepeatedPixels call, as it was not
helping much in yielding better compression density.

Before:
 1000 files, 63530337 pixels, 1 loops => 45.0s (45.0 ms/file/iterations)
 Compression (output/input): 2.463/3.268 bpp, Encode rate (raw data): 1.347 MP/s

After:
1000 files, 63530337 pixels, 1 loops => 45.9s (45.9 ms/file/iterations)
 Compression (output/input): 2.461/3.268 bpp, Encode rate (raw data): 1.321 MP/s

Change-Id: I044ba9d3f5bec088305e94a7c40c053ca237fd9d
UpdateHistogramCost: avoid implicit double->float

all the functions involved return double and later these locals are used
in double calculations. fixes a vs build warning

Change-Id: Idb547104ef00b48c71c124a774ef6f2ec5f30f14