You can now use WebPDecBuffer, WebPBitstreamFeatures and WebPDecoderOptions
to have better control over the decoding process (and the speed/quality tradeoff).
WebPDecoderOptions allow to:
- turn fancy upsampler on/off
- turn in-loop filter on/off
- perform on-the-fly cropping
- perform on the-fly rescale
(and more to come. Not all features are implemented yet).
On-the-fly cropping and scaling allow to save quite some memory
(as the decoding operation will now scale with the output's size, not
the input's one). It saves some CPU too (since for instance,
in-loop filtering is partially turned off where it doesn't matter,
and some YUV->RGB conversion operations are ommitted too).
The scaler uses summed area, so is mainly meant to be used for
downscaling (like: for generating thumbnails or previews).
Incremental decoding works with these new options.
More doc to come soon.
dwebp is now using the new decoding interface, with the new flags:
-nofancy
-nofilter
-crop top left width height
-scale width height
Change-Id: I08baf2fa291941686f4ef70a9cc2e4137874e85e
picture->error_code can be looked up for finer error diagnose.
Added readable error messages to cwebp too.
Should close bug #75 (http://code.google.com/p/webp/issues/detail?id=75)
Change-Id: I8889d06642d90702f698cd5c27441a058ddb3636
+ add a simple rescaling function: WebPPictureRescale() for encoding
+ clean-up the memory managment around the alpha plane
+ fix some includes path by using "../webp/xxx.h" instead of "webp/xxx.h"
New flags for 'cwebp':
-resize <width> <height>
-444 (no effect)
-422 (no effect)
-400
Change-Id: I25a95f901493f939c2dd789e658493b83bd1abfa
This is a (minor) bitstream change: if the 'color_space' bit is set to '1'
(which is normally an undefined/invalid behaviour), we add extra data at the
end of partition #0 (so-called 'extensions')
Namely, we add the size of the extension data as 3 bytes (little-endian),
followed by a set of bits telling which extensions we're incorporating.
The data then _preceeds_ this trailing tags.
This is all experimental, and you'll need to have
'#define WEBP_EXPERIMENTAL_FEATURES' in webp/types.h to enable this code
(at your own risk! :))
Still, this hack produces almost-valid WebP file for decoders that don't
check this color_space bit. In particular, previous 'dwebp' (and for instance
Chrome) will recognize this files and decode them, but without the alpha
of course. Other decoder will just see random extra stuff at the end of
partition #0.
To experiment with the alpha-channel, you need to compile on Unix platform
and use PNGs for input/output.
If 'alpha.png' is a source with alpha channel, then you can try (on Unix):
cwebp alpha.png -o alpha.webp
dwebp alpha.webp -o test.png
cwebp now has a '-noalpha' flag to ignore any alpha information from the
source, if present.
More hacking and experimenting welcome!
Change-Id: I3c7b1fd8411c9e7a9f77690e898479ad85c52f3e
going down to strict -ansi c89 is quite overkill (no 'inline',
and /* */-style comments).
But with these fixes, the code compiles with the stringent flags:
-Wextra -Wold-style-definition -Wmissing-prototypes
-Wmissing-declarations and -Wdeclaration-after-statement
Change-Id: I36222f8f505bcba3d9d1309ad98b5ccb04ec17e3
WebPGetDecoderVersion() and WebPGetEncoderVersion()
will not return 0.1.2 encoded as 0x000102
dwebp and cwebp also have a new "-version" flag
Change-Id: I4fb4b5a8fc4e53681a386ff4b74fffb639fa237a
The object WebPIDecoder is available to store the
decoding state. The flow is typically:
WebPIDecoder* const idec = WebPINew(mode);
while (has_more_data) {
// ... (get additional data)
status = WebPIAppend(idec, new_data, new_data_size);
if (status != VP8_STATUS_SUSPENDED ||
break;
}
// The above call decodes the current available buffer.
// Part of the image can now be refreshed by calling to
// WebPIDecGetRGB()/WebPIDecGetYUV() etc.
}
WebPIDelete(idec);
Doing so, one can try and decode new macroblocks everytime fresh
bytes are available.
There's two operating modes: either appending fresh bytes, or
updating the whole buffer with additional data in the end.
The latter requires less memcpy()'s
main patch by Somnath Banerjee (somnath at google.com)
Change-Id: Ie81cbd0b50f175743af06b1f964de838b9a10a4a
This will make the decoder skip the filtering process if needed,
resulting in speed-up, but also non-compliant (blocky?) output
+ Add a versioning check for VP8InitIo(), since we've adding a field to VP8Io
+ add some more error checks while at it
Change-Id: I4e9899edc24ecf8600cbb27aa4038490b7b2cef3
converts PNG & JPEG to WebP
This is an experimental early version, with lot of room
of later optimizations in both speed and quality.
Compile with the usual `./configure && make`
Command line example is examples/cwebp
Usage:
cwebp [options] -q quality input.png -o output.webp
where 'quality' is between 0 (poor) to 100 (very good).
Typical value is around 80.
More encoding options with 'cwebp -longhelp'
Change-Id: I577a94f6f622a0c44bdfa9daf1086ace89d45539
When FANCY_UPSCALING is defined, use a smoothing filter for upscaling
the U/V chroma fields. The filter used is a separable t[1 3 3 1] x [1 3 3 1]
filter. It can be easily changed in macros MIX_*.
The upscaling code reside on the thing shell between user and core
decoding (in webp.c), and not in the core decoder. As such, this smoothing
process can still be offloaded to GPU in some future and is not integral
part of the decoding process.
Coincidentaly: changed the way data is tranfered to user. For profile 2 (no
filtering), it used to be on a per-block basis. Now, for all profiles, we
emit rows of pixels (between 8 and 24 in height) when they are ready.
This makes the upscaling code much easier.
Will update the test vectors MD5 sums soon (as they'll be broken
after this change)
Change-Id: I2640ff12596cb8b843a4a376d7347447d9b9f778
