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add a WebPCleanupTransparentArea() method

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to 'clean up' the fully-transparent area and make it more compressible
new cwebp flags: -alpha_cleanup (off by default, since gain is not 100% guaranteed)

Change-Id: I74d77e1915eee146584cd61c9c1132a41db922eb
This commit is contained in:
Pascal Massimino
2012-01-17 08:18:22 +00:00
committed by James Zern
parent 552c121715
commit 2e3e8b2ef5
5 changed files with 93 additions and 8 deletions
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15
README
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@@ -121,19 +121,21 @@ A longer list of options is available using the -longhelp command line flag:
Usage:
cwebp [-preset <...>] [options] in_file [-o out_file]
If input size (-s) for an image is not specified, it is assumed to be a either
PNG or JPEG format file.
If input size (-s) for an image is not specified, it is assumed to be a
PNG or JPEG file.
options:
-h / -help ............ short help
-H / -longhelp ........ long help
-q <float> ............. quality factor (0:small..100:big)
-alpha_q <int> ......... Transparency-compression quality (0..100)
-alpha_q <int> ......... Transparency-compression quality (0..100).
-preset <string> ....... Preset setting, one of:
default, photo, picture,
drawing, icon, text
-preset must come first, as it overwrites other parameters.
-m <int> ............... compression method (0=fast, 6=slowest)
-segments <int> ........ number of segments to use (1..4)
-size <int> ............ Target size (in bytes)
-psnr <float> .......... Target PSNR (in dB. typically: 42)
-s <int> <int> ......... Input size (width x height) for YUV
-sns <int> ............. Spatial Noise Shaping (0:off, 100:max)
@@ -143,7 +145,6 @@ options:
-partition_limit <int> . limit quality to fit the 512k limit on
the first partition (0=no degradation ... 100=full)
-pass <int> ............ analysis pass number (1..10)
-partitions <int> ...... number of partitions to use (0..3)
-crop <x> <y> <w> <h> .. crop picture with the given rectangle
-resize <w> <h> ........ resize picture (after any cropping)
-map <int> ............. print map of extra info.
@@ -151,6 +152,7 @@ options:
-alpha_method <int> .... Transparency-compression method (0..1)
-alpha_filter <string> . predictive filtering for alpha plane.
One of: none, fast (default) or best.
-alpha_cleanup ......... Clean RGB values in transparent area.
-noalpha ............... discard any transparency information.
-short ................. condense printed message
@@ -160,11 +162,8 @@ options:
-v ..................... verbose, e.g. print encoding/decoding times
-progress .............. report encoding progress
Experimental Options:
-size <int> ............ Target size (in bytes)
-psnr <float> .......... Target PSNR (in dB. typically: 42)
-af <int> .............. adjust filter strength (0=off, 1=on)
-af .................... auto-adjust filter strength.
-pre <int> ............. pre-processing filter