copy and paste error in the previous commit, change
no_sanitize("unsigned-integer-overflow") from WEBP_UBSAN_IGNORE_UNDEF ->
WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW
Change-Id: Id178ee14df1f2c4923a91ce423241e26b60b5d32
include utils.h directly where needed to allow utils.h to rely on
defines from dsp.h in a follow-up.
Change-Id: I32e26aaeb0b04ba60b3332f685f9a2be5a0a8d3d
configure gets 2 new options:
--enable-neon / --enable-neon-rtcd
the NEON modules are split to their own convenience lib and built with
auto-detected flags if none are given via CFLAGS.
the /proc/cpuinfo check will only be used for armv7 targets whose
toolchain does not enable NEON by default or didn't have NEON forced by
the CFLAGS from the environment.
Change-Id: I2755bc1d065d5d6ee6143b44978c2082f8bef1c5
This will allow to work in-place on cropped area later.
Also sped up the inverse gradient filtering in SSE2 (~4%)
Change-Id: I463149eee95d36984328f163a1e17f8cabd87441
This is in preparation for some SSE2 code.
And generally speaking, the whole SSIM code needs some
revamp: we're not averaging the SSIM value at each pixels
but just computing the overall SSIM value once, for the whole
plane. The former might be better than the latter.
Change-Id: I935784a917f84a18ef08dc5ec9a7b528abea46a5
based on the sse2 change in:
9960c31 Remove an unnecessary transposition in TTransform.
~9-10.5% faster at the function-level, < 1% overall
Change-Id: I44413369b230b250fb0dbc51ff2f17cfeda609b7
SSE4.1 is slower than the SSE2 implementation and this seems to
be due to a slow _mm_loadl_epi64 implementation by gcc
(hence a bug with my gcc 4.8) and a very slow _mm_hadd_epi32. Both
got confirmed by IACA and experiments.
Change-Id: I05607f66b7ccd8f4f42e000693aea583ffd5768f
The transpose refactoring will help removing a transpose in a
later CL.
The horizontal add function helps removing a _mm_sad_epu8 in DC8uv
=> the latency/throughput went from 29/25 to 23/19
Change-Id: I5f3dfd4aad614eb079b1e83631e6a7cef49a3766
'implicit conversion from 'int' to 'short' changes value from 33050 to
-32486'
original patch:
https://codereview.chromium.org/1657313003/
Make libwebp build with -Wconstant-conversion from newer clangs.
After http://llvm.org/viewvc/llvm-project?rev=259271&view=rev, clang
points out that _mm_set1_epi16(33050) causes an overflow in the short
argument to _mm_set1_epi16(). Since there's no version that takes an
unsigned short, add an explicit cast to tell the compiler that this is
intentional.
No behavior change.
Change-Id: I6b4e3401b15cfbcc895f9e81b5c2dc59d43ffb9b
The code and logic is unified when computing bit entropy + Huffman cost.
Speed-wise, we gain 8% for lossless encoding.
Logic-wise, the beginning/end of the distributions are handled properly
and the compression ratio does not change much.
Change-Id: Ifa91d7d3e667c9a9a421faec4e845ecb6479a633
The functions containing magic constants are moved out of ./dsp .
VP8LPopulationCost got put back in ./enc
VP8LGetCombinedEntropy is now unrefined (refinement happening in ./enc)
VP8LBitsEntropy is now unrefined (refinement happening in ./enc)
VP8LHistogramEstimateBits got put back in ./enc
VP8LHistogramEstimateBitsBulk got deleted.
Change-Id: I09c4101eebbc6f174403157026fe4a23a5316beb
This implementation brings:
- an SSE implementation of packing / unpacking
- bigger buffers processed at the same time
The speedup is of 4% on lossy decoding (YUV to RGB), 0.5% on
lossy encoding (RGB to YUV was already optimized).
Change-Id: Iec677ee17f91c08614d1adab67c6df551925767f
INFO: From Compiling src/dsp/cpu.c:
src/dsp/cpu.c: In function 'x86CPUInfo':
src/dsp/cpu.c:36:3: inconsistent operand constraints in an 'asm'
With PIC and mcmodel=medium, the %rbx register must be saved and
restored which causes this problem. This was also solved in GCC-4.9 with
this patch:
https://gcc.gnu.org/ml/gcc-patches/2012-12/msg01484.html
Tested:
Builds fine with this change.
Change-Id: Icca8eea7bf5af3ef9f17f6ae2886e3430143febf
CombinedShannonEntropy takes 30% for lossless compression.
This implementation speeds up the overall process by 2 to 3 %.
Change-Id: I04a71743284c38814fd0726034d51a02b1b6ba8f
* Precision is slightly different
* also implemented in SSE2 the missing WebPUpsamplers for MODE_ARGB, MODE_Argb, MODE_RGB565, etc.
* removing yuv_tables_sse2.h saved ~8k of binary size
* the mips32/mips_dsp_r2 code is disabled for now, since it has drifted away
* the NEON code is somewhat tricky
Change-Id: Icf205faa62cf46c2825d79f3af6725dc1ec7f052
Gives 0.9% smaller (2.4% compared to before alpha cleanup) size on the 1000 PNGs dataset:
Alpha cleanup before: 18856614
Alpha cleanup after: 18685802
For reference, with no alpha cleanup: 19159992
Note: WebPCleanupTransparentArea is still also called in WebPEncode. This cleanup still helps
preprocessing in the encoder, and the cases when the prediction transform is not used.
Change-Id: I63e69f48af6ddeb9804e2e603c59dde2718c6c28
for more speed.
This gives a roughly a 1% speedup for low_effort. But actually this is a
preparation for the upcoming CL that changes RGB values of transparent pixels
based on prediction, which should not be done for low_effort because that would
slightly hurt its performance.
On 1000 PNGs, with quality 0, method 0:
Before:
Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 36.034 MP/s
After:
Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 36.428 MP/s
Change-Id: I5ed9f599bbf908a917723f3c780551ceb7fd724d
The same computation was done for both values: go over two buffers,
sum them up, and take a decision on the sum at each iteration.
MIPS32 code has been disabled for now, pending a code update.
Change-Id: I997984326f7092b3dbb8cfa1e524bd8132b2ab9d
instead of per block. This prepares for a next CL that can make the
predictors alter RGB value behind transparent pixels for denser
encoding. Some predictors depend on the top-right pixel, and it must
have been already processed to know its new RGB value, so requires per
scanline instead of per block.
Running the encode speed test on 1000 PNGs 10 times with default
settings:
Before:
Compression (output/input): 2.3745/3.2667 bpp, Encode rate (raw data): 1.497 MP/s
After:
Compression (output/input): 2.3745/3.2667 bpp, Encode rate (raw data): 1.501 MP/s
Same but with quality 0, method 0 and 30 iterations:
Before:
Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 36.379 MP/s
After:
Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 36.462 MP/s
No effect on compressed size, this produces exactly same files. No
significant measured effect on speed. Expected faster speed from better
memory layout with scanline processing but slower speed due to needing
to get predictor mode per pixel, may compensate each other.
Change-Id: I40f766f1c1c19f87b62c1e2a1c4cd7627a2c3334
the problem was the incorporation of the extra constant 1<<16 in the kC1
constant, to emulate the addition. It's now removed and the addition is
performed explicitly.
No real speed difference observed.
cf. issue #278
Change-Id: I2c6499031571d98afff392fb5ebe21a5fa60722d
global effect is ~2% faster encoding from JPG source
and ~8% faster lossless-webp source decoding to PGM (e.g.)
Also revamped the YUVA case to first accumulate R/G/B value into 16b
temporary buffer, and then doing the UV conversion.
-> New function: WebPConvertRGBA32ToUV
Change-Id: I1d7d0c4003aa02966ad33490ce0fcdc7925cf9f5
Just for RGB24/BGR24 for now, which are the hard-to-optimize ones.
SSE2 implementation coming next.
ConvertRowToY() should go into dsp/ too, at some point.
Change-Id: Ibc705ede5cbf674deefd0d9332cd82f618bc2425
also switch to using ExtractAlpha() instead of hard-coding the loop.
The ARGBToY/UV functions are rather easy to port to SSE2 / NEON.
Change-Id: I8f1346a9ca427a36ce2d6c848369ca7964d8b3c7
use 'u' rather than the unnecessary 'l' as a suffix. this prevents a
conversion warning with some toolchains
Change-Id: I21c33ce08819b3c839c75e03a8f7f3a6041d0695
same functionality, but better code layout.
What changed:
* don't trash the palette_[] in EncodePalette(), so it can be re-used
* split generation of image from bit-stream coding
* move all the delta-palette code to delta_palettization.c, and only have 1 entry point there WebPSearchOptimalDeltaPalette()
* minimize the number of "#ifdef WEBP_EXPERIMENTAL_FEATURES" in vp8l.c
* clarify the TransformBuffer stuff. more clean-up to come here...
This should make experimenting with delta-palettization easier and more compartimentalized.
Change-Id: Iadaa90e6c5b9dabc7791aec2530e18c973a94610
some limitations: only for RGBA output,
and if reduction factor is not too small (dst_width > src_width / 128)
20-25% faster, ~4-6% global improvement total decoding.
Change-Id: I95366ddaa4a38e0a96bed754dfe790126f7bb84a
It's better to stay with a 32b fixed-point precision overall, otherwise
the C-version on ARM gets *slower*.
Actually, gcc ARM compiler optimizes some instructions pretty
well when WEBP_RESCALER_FIX is exactly 32, even in C.
Change-Id: I0eea97f7db5947470f5af355dee098eca81e178d
The rounding and arithmetic is not the same as previously, to prevent overflow cases for large upscale factors.
We still rely on 32b x 32b -> 64b multiplies. Raised the fixed-point precision to 32b
so that we have some nice shifts from epi64 to epi32.
Changed rescaler_t type to 'uint32_t' in order to squeeze in all the precision required.
The MIPS code has been disabled because it's now out-of-sync. Will be fixed in
a subsequent CL when the dust settles.
~30-35% faster
Change-Id: I32e4ddc00933f1b1aa3463403086199fd5dad07b
* vertical expansion now uses bilinear interpolation
* heavily assumes that the alpha plane is decoded in full, not row-by-row
* split the RescalerExportRow and RescalerImportRow methods into Shrink
and Expand variants.
* MIPS implementation of ExportRowExpand is missing.
There's room for extra speed optim and code re-org, but let's keep that for later patches.
addresses https://code.google.com/p/webp/issues/detail?id=254
Change-Id: I8f12b855342bf07dd467fe85e4fde5fd814effdb
the x_add/x_sub increments were wrong for u/v in the upscaling case.
They shouldn't be left to the caller's discretion, but set up by
WebPRescalerInit to their exact necessary values.
-> Cleaned-up WebPRescalerInit() param list.
-> added safety asserts
-> removed the mips32/mips_r2 variant of "ImportRow" which were buggy prior
Change-Id: I347c75804d835811e7025de92a0758d7929dfc09
this moves the function outside the WEBP_USE_INTRINSICS check.
there's no alternative version and it's ~54% faster at the
function level and mildly faster overall
Change-Id: Ibc648e9ee35021d48901e05aa596aa01067796a2
share the computation between different modes
3-5 % speedup for lossless alpha
1 % for lossy alpha
no change in compression density
Change-Id: I5e31413b3efcd4319121587da8320ac4f14550b2
After several trials at re-organizing the main loop and accumulation scheme,
this is apparently the faster variant.
removed the SSE41 version, which is no longer faster now.
For some reason, the AVX variant seems to benefit most for the change.
Change-Id: Ib11ee18dbb69596cee1a3a289af8e2b4253de7b5
this moves the function outside the WEBP_USE_INTRINSICS check.
there's no alternative version and it's ~70% faster at the
function level and 1-2% faster overall
Change-Id: I59fb4918ec86b1ac3a47cbd5d05ce62f007461cb
Changed the code (again) to process 4 pixels at a time. Loop is more
involved, but overall it's faster.
Removed the SSE4.1 implementation which is now slower than SSE2.
Change-Id: I7734e371033ad8929ace7f7e1373ba930d9bb5f1
New implementations: SubtractGreenFromBlueAndRed and TransformColor
around 1-2% faster lossless encoding.
Change-Id: I1668e36fdc316ba55b3b798b91b4a3e36ce62861
DispatchAlpha* functions are hard to speed up, compared to SSE2.
ExtractAlpha sees a ~15% speed-up though.
Change-Id: I8715c2defecbc832f469eed7e6ffd012146b52de
over a 1000 image corpus
Single photograph benchmark:
Before:
Q=20: 2.560 MP/s
Q=40: 2.593 MP/s
Q=60: 1.795 MP/s
Q=80: 1.603 MP/s
Q=99: 1.122 MP/s
After:
Q=20: 3.334 MP/s
Q=40: 2.464 MP/s
Q=60: 2.009 MP/s
Q=80: 1.871 MP/s
Q=99: 1.163 MP/s
This CL allows for some further improvements that would not be possible
otherwise.
Change-Id: I61ba154beca2266cb96469281cf96e84a4412586
use vld1_dup_u8() rather than a separate ld+dup after the values were
zero extended; mildly faster at the function level
Change-Id: I1b3666a6aeb465722a1214dbc6d71c27689a7f89
VP8EncPredChroma8 improvements over ~20M pixels
left/top: ~67%
left-only: ~52%
top-only: ~57%
none: ~61%
based on dec_sse2 versions with minor changes to benefit from the linear
storage of the left boundary
Change-Id: Iee7e387fb2570b4eb5af5bfd123e9c2e9ea49c76
VP8EncPredLuma16 improvements over ~20M pixels
left/top: ~75%
left-only: ~47%
top-only: ~59%
none: ~63%
based on dec_sse2 versions with minor changes to benefit from the linear
storage of the left boundary
Change-Id: I7548be7214fa85c38fd11d30f5b8b271f437657d
structured extended feature flags require eax = 7; avoids incorrectly
detecting avx2 on some older processors that support avx.
for completeness also check for value=1 support used by the other
checks.
from [1]:
INPUT EAX = 0: Returns CPUID’s Highest Value for Basic Processor
Information and the Vendor Identification String
[1]
http://www.intel.com/content/www/us/en/processors/processor-identification-cpuid-instruction-note.html
Change-Id: I60b20d661a978d551614dbf7acdc25db19cb6046
use psadbw to perform top row summation; left remains in C as repacking
it into a vector to apply the same operation is too costly.
DC8uv: ~19% faster
DC8uvNoLeft: ~12% faster
Change-Id: I707c4f6177a65b5d1f2d3deeca87d2bb740185e2
use psadbw to perform top row summation; left remains in C as repacking
it into a vector to apply the same operation is too costly.
DC16: ~20% faster
DC16NoLeft: ~14% faster
Change-Id: I7ec3f8a6e5923f88a530f79fceb88d5001bef691
generates a stub function when the specific architecture is not enabled,
exposing a symbol in the module, avoiding a compiler warning
Change-Id: Ia9336e57466a9b5241b85c1c95838e91c9283147
Visible speed-up, thanks to pshufb and pabsw and psignw use.
had to tweak configure.ac to make "smmintri.h" presence correctly
detected (we need to set the CPPFLAGS instead of the CFLAGS!)
Change-Id: I2ab99e16a27a64fdf1f09b2b4e30a5e74ccca080
allows the former to be inlined; negligible speed-up in most cases,
however this is structure is consistent with the rest of the optimized
modules
Change-Id: Ib080240b06f7a995b47f1906627850c355b82901
the standard vtbl functions are available there [1][2].
based on a patch from: aaroncrespo
fixes issue #243.
[1]
http://adcdownload.apple.com//Developer_Tools/Xcode_6.3_beta/Xcode_6.3_beta_Release_Notes.pdf
[2] Apple LLVM Compiler Version 6.1
- Xcode 6.3 updates the Apple LLVM compiler to version 6.1.0.
[...]
Support for the arm64 architecture has been significantly revised to
align with ARM's implementation, where the most visible impact is that a
few of the vector intrinsics have changed to match ARM's specifications.
Change-Id: I79a0016f44b9dbe36d0373f7f00a50ab3c2ca447
The MIPS code for cost is not updated yet, that's why i keep Residual::*cost
around for now. Should be removed in favor of *costs later.
Change-Id: Id1d09a8c37ea8c5b34ad5eb8811d6a3ec6c4d89f
affected functions: SimpleVFilter16, SimpleHFilter16,
SimpleVFilter16i and SimpleHFilter16i
noticed bug in FilterLoop26 (fix included in this patch)
Change-Id: I72d9c1e45cbac6393eba52bb549b04924d463e30
removes circular dependency between dsp and enc.
since:
a987fae MIPS: dspr2: added optimization for function GetResidualCost
Change-Id: Ifeb8fc02de89e2ba982ed7ffacd925d649bfec3c
set/get residual C functions moved to new file in src/dsp
mips32 version of GetResidualCost moved to new file
Change-Id: I7cebb7933a89820ff28c187249a9181f281081d2
similar to:
1ba61b0 enable NEON intrinsics in aarch64 builds
vtbl1_u8 is available everywhere but Xcode-based iOS arm64 builds, use
vtbl1q_u8 there.
performance varies based on the input, 1-3% on encode was observed
Change-Id: Ifec35b37eb856acfcf69ed7f16fa078cd40b7034
The 'inverse' variants are harder to parallelize, since
the result of filtering is used for prediction.
The 'direct' way is relatively easier.
The heavy bottleneck left for optimization is still GradientUnfilter()
Change-Id: I358008f492a887e8fff6600cb27857b18dee86e9
and only use it on x86 / x64 where it's available.
has the side-effect of quieting a msvs /analyze warning:
C6001: Using uninitialized memory 'cpu_info'.
Change-Id: Iae51be3b22b2ee949cfc473eeea9fd9fb6b3c2cb
added new function CollectColorRedTransforms to C, which calls
TransformColorRed and it is realized via pointer to function
Change-Id: Ia68d73bfcf1ca2cb443dc2825910946221f87835
explicitly add immintrin.h instead of transitively picking it up via
windows.h presumably. makes the code easier to move around.
Change-Id: If70d5143ac94fc331da763ce034358858e460e06
added new function CollectColorBlueTransforms to C, which calls
TransformColorBlue and it is realized via pointer to function
Change-Id: Ia488b7a7a689223b5d33aae9724afab89b97fced
we compare the current VP8GetCPUInfo pointer to the last used.
This is less code overall and each implementation is still
testable separately (by just changing VP8GetCPUInfo, but not
a separate threads!)
Change-Id: Ia13fa8ffc4561a884508f6ab71ed0d1b9f1ce59b
inline function MakeARGB32 calls changed to call
via pointers to functions which make (a)rgb for
entire row
Change-Id: Ia4bd4be171a46c1e1821e408b073ff5791c587a9
and apply Paeth predictor (predictor#11) for the low effort (m=0) mode.
For 1000 image PNG corpus (m=0), this change yields speedup of 25% at lower quality
range and about 10% for higher quality range.
Change-Id: I0f036b8ffe45c241e63a067cbf01527b13d8de93
check for __apple_build_version__ to distinguish the two; a version
check could work as Apple bumped Xcode's to 5.x/6.x, but it's unclear
how upstream will deal with their versioning as they go 3.6+, so avoid
it for now.
Change-Id: I67cda67c4f68e262a92d805a63cc1496374be063
we don't need to store the whole distribution in order to compute the alpha
Later, we can incorporate the max_value / last_non_zero bookkeeping
in SSE2 directly.
Change-Id: I748ccea4ac17965d7afcab91845ef01be3aa3e15
this is a first step to unifying encoding/decoding cache stride
and possibly sharing the prediction functions in dsp/
With this layout, there's a little (~7%) space lost with unused samples.
But no speed change was observed.
Change-Id: I016df8cad41bde5088df3579e6ad65d884ee711e
~68% faster
reuses TM4() adding support for the additional rows, the columns were
already being done.
Change-Id: I6eac17e58cd1c636082bf7281f70f884ec399a6b
Move all the Entropy evaluation methods to lossless.c (from histogram.c).
There's slight difference in the way entropy is computed for evaluating
entropy in prediction methods and histogram (literal) for huffman trees.
Plan (later) to merge few (static) methods and reduce the code size.
This change has no impact on the compression speed/density.
Change-Id: Ife3d96a3c4a8d78a91723d9e0a8d1b78c0256a15
set WEBP_EXTERN to visibility=default
+ explicitly mark VP8GetCPUInfo as it's referenced within the examples
Change-Id: Ie3d2b15088e888f0b55203b205993eba75899d99
move the attribute to the front of the function to quiet clang warning:
GCC does not allow no_sanitize_thread attribute in this position on a
function definition
Change-Id: Ie4cc6e35a07bd00eab67d9cd6801bd2be9cfe676
avoids an ICE with NDK r10b + NDK_TOOLCHAIN_VERSION=4.9
In function 'SSE16x16':
enc_mips32.c (684) internal compiler error: Segmentation fault
Change-Id: I1a3d33c0a9534c97633ab93bcdf9bf59d3a7e473
got rid of the |a-b|^|b-a| method and went back
to just (a-b)^2 instead.
quality | size(bytes) after/before | time (ms) after/before
Change-Id: Ia3e0e6507b3f903deb1e182f78dad6df07380fd0
SSE2 version is 2.1x faster
This is used to transfer the alpha plane to green channel before lossless compression.
Change-Id: I01d9df0051c183b1ff5d6eb69961d4f43e33141a
* We were re-doing most of the work in plain-C as 'left-over'.
* we were always returning has_alpha = true because of a bad mask all_0xff
These bugs were conservative and silent, in the sense that we were 'just' doing
more work than necessary.
Now, the SSE2 version is really 2x faster than the C version.
Change-Id: I6c8132a267fe3c7a3d1fa70e7a5fcd10719543fa
Split initialization of YUV444Converters[] out of Upsamplers init.
update test for NULL function pointers
Change-Id: I9603f54250f90c85a12ffbecfd6c59e9b06c47e0
vtbl4_u8 is available everywhere except iOS arm64: use vtbl2q_u8 there
with a corresponding change in the load.
Change-Id: Ib84212dda3c7875348282726c29e3b79b78b0eac
_M_IX86 will be defined in mingw builds after including windows.h. as
the gcc inline asm is first, this missing check would only have caused
an error if the code was reorganized.
Change-Id: I395679bcfc43e94d308d1ceb0c0fbf932b2c378c
this defines WORDS_BIGENDIAN, replacing uses of
__BIG_ENDIAN__/__BYTE_ORDER__ with it
+ fixes lossless BGRA output with big-endian toolchains
that do not define __BIG_ENDIAN__ (codesourcery mips gcc)
Change-Id: Ieaccd623292d235343b5e34b7a720fc251c432d7
this will remove a warning about the shift amount not being
an immediate (=constant).
Change-Id: Ie9a00fefdb9a07ec8994fb113f24234518bc878a
Also: fix the NULL sharpen argument mismatch.
Another store to load forward block was detected coming from the function
FTransform.
FTransform save the output data 4 times 8 bytes each. when this data is
later being loaded by the QuantizeBlock function in one chunk of 16 bytes
that caused a store to load forward block.
The fix was done in the FTransform function where each two consecutive 8 bytes
were merged into one 16 bytes register and saved into the memory.
This fix gives ~21% function level gain and 1.6% user level gain.
Change-Id: Idc27c307d5083f3ebe206d3ca19059e5bd465992
only 1 of <lib>_CPPFLAGS and AM_CPPFLAGS is used, with the former
getting precedence when it's defined. configure's DEFAULT_INCLUDES is
covering what's necessary given the include paths are all source
relative.
Change-Id: I7d14076acd266b28a88a3d92bcc3d7165284d5f3
this change has the side-effect of using directory names in the
include, silencing a lint warning.
Change-Id: Ib91cf63a90534e32fadfa5c2372bfdb29f854d02
if res->first = 1, coeffs[0]=0 because of quant.c:749 and line
added at quant.c:744
So, no need for the extra case.
Going forward, TrellisQuantizeBlock() should also be calling
a variant of VP8SetResidualCoeffs() to set the 'last' field.
also: fixes a warning for win64
+ slight speed-up
Change-Id: Ib24b611f7396d24aeb5b56dc74d5c39160f048f0
+ add a WEBP_HAVE_SSE2 to dsp.h
not all 32-bit toolchain configurations will have sse2 enabled by
default
Change-Id: I7c675e511581f93cf55c79f960fa7efa2df4987e
this is used to set WEBP_USE_AVX2 in files where the build flag won't be
used, i.e., dsp/enc.c, which enables VP8EncDspInitAVX2() to be called
Change-Id: I362f4ba39ca40d3e07a081292d5f743c649d9d7f
Extract loop invariant and avoid storing/loading samples
if they can be re-used. This is particularly interesting when
a transpose is involved (HFilter16i).
Change-Id: I93274620f6da220a35025ff8708ff0c9ee8c4139
The luminance needs to be pre- and post- multiplied by
the alpha value in case of rescaling, for proper averaging.
Also:
- removed util/alpha_processing and moved it to dsp/
- removed WebPInitPremultiply() which was mostly useless
and merged it with the new function WebPInitAlphaProcessing()
Change-Id: If089cefd4ec53f6880a791c476fb1c7f7c5a8e60
