* remove the sharpening for non luma-AC coeffs
* adjust the bias a little bit to compensate for this
Using the multiply-by-reciprocal doesn't always give the same result
as the exact divide, given the QFIX fixed-point precision we use.
-> removed few now-unneeded SSE2 instructions (and checked for
bit-exactness using -noasm)
Change-Id: Ib68057cbdd69c4e589af56a01a8e7085db762c24
original/compressed pictures were not converted to an adequate YUVA
colorspace before computing the distortion.
Change-Id: I37775e9b7dbd6eca16c38e235e1df325858d36a1
-ffunction-sections / -fdata-sections
can improve final binary size when used with --gc-sections, speed impact
untested
Change-Id: I37f4b5da2f34acede7965c2da2e1b97125473adc
Even at high quality setting, the U/V quantizer step is limited
to 4 which can lead to banding on gradient.
This option allows to selectively apply some randomness to
potentially flattened-out U/V blocks and attenuate the banding.
This option is off by default in 'dwebp', but set to -dither 50
by default in 'vwebp'.
Note: depending on the number of blocks selectively dithered,
we can have up to a 10% slow-down in decoding speed it seems.
Change-Id: Icc2446007f33ddacb60b3a80a9e63f2d5ad162de
RGBToU/V calls expects two extra precision bits, they were only
given one by SUM2H and SUM2H macros.
For rounding coherency, also changed SUM1 macro.
Change-Id: I05f96a46f5d4f17b830d0420eaf79b066cdf78d4
When '-mixed' option is given, each frame would be heuristically chosen
to be
encoded using lossy or lossless compression.
The heuristic is based on the number of colors in the image:
- If num_colors <= 31, pick lossless compression
- If num_colors >= 194, pick lossy compression
- Otherwise, try both and pick the one that compresses better.
Change-Id: I908c73493ddc38e8db35b7b1959300569e6d3a97
otherwise make sure that all frames are marked as a fragment. there's
still some work to do with validation if fragments are expected to cover
the entire canvas.
Change-Id: Id59e95ac01b9340ba8c6039b0c3b65484b91c42f
This is to conform to man/gif2webp.1
Earlier, one needed to give both '-kmin 0' and '-kmax 0' for this to
work.
Also, suppress further warnings for kmin = 0 and/or kmax = 0 case.
Change-Id: I6f5eeb609aeffc159d0252a40a5734162f7e4e7d
this avoids local-minima that look bad, even if the distortion
looks low (e.g. gradients, sky,...). Mostly visible in the q=50-80 range.
Output size is mostly unchanged.
Change-Id: I425b600ec45420db409911367cda375870bc2c63
Earlier we were only testing for bit_pos == LBITS. But this is not
sufficient,
as bit_pos can jump from < LBITS to > LBITS.
This was resulting in some bit-stream truncation errors not being
caught.
Note: Not a security bug though, as br->pos wasn't incremented in such
cases
and so we weren't reading beyond the buffer.
Change-Id: Idadcdcbc6a5713f8fac3470f907fa37a63074836
* raise U/V quantization bias to more neutral values
* also raise the non-zero AC bias for Y1/Y2 matrices
(we need all the precision we can for U/V leves, which are often empty)
This will increase quality in the higher range (q >= 90) mostly.
Files size is exacted to raise a little (5-7%). and SSIM accordingly of course.
Change-Id: I8a9ffdb6d8fb6dadb959e3fd392e66dc5aaed64e
