Green Sky
67653bbe50
git-subtree-dir: external/libwebp/libwebp git-subtree-split: dd7364c3cefe0f5c0b3c18c3b1887d353f90fc1f
517 lines
18 KiB
Markdown
517 lines
18 KiB
Markdown
# WebP tools
|
|
|
|
## Encoding tool
|
|
|
|
The examples/ directory contains tools for encoding (cwebp) and decoding (dwebp)
|
|
images.
|
|
|
|
The easiest use should look like:
|
|
|
|
```shell
|
|
cwebp input.png -q 80 -o output.webp
|
|
```
|
|
|
|
which will convert the input file to a WebP file using a quality factor of 80 on
|
|
a 0->100 scale (0 being the lowest quality, 100 being the best. Default value is
|
|
75).
|
|
|
|
You might want to try the `-lossless` flag too, which will compress the source
|
|
(in RGBA format) without any loss. The `-q` quality parameter will in this case
|
|
control the amount of processing time spent trying to make the output file as
|
|
small as possible.
|
|
|
|
A longer list of options is available using the `-longhelp` command line flag:
|
|
|
|
```shell
|
|
> cwebp -longhelp
|
|
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 PNG,
|
|
JPEG, TIFF or WebP file. Note: Animated PNG and WebP files are not supported.
|
|
|
|
Options:
|
|
|
|
```
|
|
-h / -help ............. short help
|
|
-H / -longhelp ......... long help
|
|
-q <float> ............. quality factor (0:small..100:big), default=75
|
|
-alpha_q <int> ......... transparency-compression quality (0..100),
|
|
default=100
|
|
-preset <string> ....... preset setting, one of:
|
|
default, photo, picture,
|
|
drawing, icon, text
|
|
-preset must come first, as it overwrites other parameters
|
|
-z <int> ............... activates lossless preset with given
|
|
level in [0:fast, ..., 9:slowest]
|
|
|
|
-m <int> ............... compression method (0=fast, 6=slowest), default=4
|
|
-segments <int> ........ number of segments to use (1..4), default=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), default=50
|
|
-f <int> ............... filter strength (0=off..100), default=60
|
|
-sharpness <int> ....... filter sharpness (0:most .. 7:least sharp), default=0
|
|
-strong ................ use strong filter instead of simple (default)
|
|
-nostrong .............. use simple filter instead of strong
|
|
-sharp_yuv ............. use sharper (and slower) RGB->YUV conversion
|
|
-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)
|
|
-qrange <min> <max> .... specifies the permissible quality range
|
|
(default: 0 100)
|
|
-crop <x> <y> <w> <h> .. crop picture with the given rectangle
|
|
-resize <w> <h> ........ resize picture (*after* any cropping)
|
|
-mt .................... use multi-threading if available
|
|
-low_memory ............ reduce memory usage (slower encoding)
|
|
-map <int> ............. print map of extra info
|
|
-print_psnr ............ prints averaged PSNR distortion
|
|
-print_ssim ............ prints averaged SSIM distortion
|
|
-print_lsim ............ prints local-similarity distortion
|
|
-d <file.pgm> .......... dump the compressed output (PGM file)
|
|
-alpha_method <int> .... transparency-compression method (0..1), default=1
|
|
-alpha_filter <string> . predictive filtering for alpha plane,
|
|
one of: none, fast (default) or best
|
|
-exact ................. preserve RGB values in transparent area, default=off
|
|
-blend_alpha <hex> ..... blend colors against background color
|
|
expressed as RGB values written in
|
|
hexadecimal, e.g. 0xc0e0d0 for red=0xc0
|
|
green=0xe0 and blue=0xd0
|
|
-noalpha ............... discard any transparency information
|
|
-lossless .............. encode image losslessly, default=off
|
|
-near_lossless <int> ... use near-lossless image preprocessing
|
|
(0..100=off), default=100
|
|
-hint <string> ......... specify image characteristics hint,
|
|
one of: photo, picture or graph
|
|
|
|
-metadata <string> ..... comma separated list of metadata to
|
|
copy from the input to the output if present.
|
|
Valid values: all, none (default), exif, icc, xmp
|
|
|
|
-short ................. condense printed message
|
|
-quiet ................. don't print anything
|
|
-version ............... print version number and exit
|
|
-noasm ................. disable all assembly optimizations
|
|
-v ..................... verbose, e.g. print encoding/decoding times
|
|
-progress .............. report encoding progress
|
|
```
|
|
|
|
Experimental Options:
|
|
|
|
```
|
|
-jpeg_like ............. roughly match expected JPEG size
|
|
-af .................... auto-adjust filter strength
|
|
-pre <int> ............. pre-processing filter
|
|
```
|
|
|
|
The main options you might want to try in order to further tune the visual
|
|
quality are:
|
|
|
|
-preset -sns -f -m
|
|
|
|
Namely:
|
|
|
|
* `preset` will set up a default encoding configuration targeting a particular
|
|
type of input. It should appear first in the list of options, so that
|
|
subsequent options can take effect on top of this preset. Default value is
|
|
'default'.
|
|
* `sns` will progressively turn on (when going from 0 to 100) some additional
|
|
visual optimizations (like: segmentation map re-enforcement). This option
|
|
will balance the bit allocation differently. It tries to take bits from the
|
|
"easy" parts of the picture and use them in the "difficult" ones instead.
|
|
Usually, raising the sns value (at fixed -q value) leads to larger files,
|
|
but with better quality. Typical value is around '75'.
|
|
* `f` option directly links to the filtering strength used by the codec's
|
|
in-loop processing. The higher the value, the smoother the highly-compressed
|
|
area will look. This is particularly useful when aiming at very small files.
|
|
Typical values are around 20-30. Note that using the option
|
|
-strong/-nostrong will change the type of filtering. Use "-f 0" to turn
|
|
filtering off.
|
|
* `m` controls the trade-off between encoding speed and quality. Default is 4.
|
|
You can try -m 5 or -m 6 to explore more (time-consuming) encoding
|
|
possibilities. A lower value will result in faster encoding at the expense
|
|
of quality.
|
|
|
|
## Decoding tool
|
|
|
|
There is a decoding sample in examples/dwebp.c which will take a .webp file and
|
|
decode it to a PNG image file (amongst other formats). This is simply to
|
|
demonstrate the use of the API. You can verify the file test.webp decodes to
|
|
exactly the same as test_ref.ppm by using:
|
|
|
|
```shell
|
|
cd examples
|
|
./dwebp test.webp -ppm -o test.ppm
|
|
diff test.ppm test_ref.ppm
|
|
```
|
|
|
|
The full list of options is available using -h:
|
|
|
|
```shell
|
|
> dwebp -h
|
|
Usage: dwebp in_file [options] [-o out_file]
|
|
```
|
|
|
|
Decodes the WebP image file to PNG format [Default]. Note: Animated WebP files
|
|
are not supported.
|
|
|
|
Use following options to convert into alternate image formats:
|
|
|
|
```
|
|
-pam ......... save the raw RGBA samples as a color PAM
|
|
-ppm ......... save the raw RGB samples as a color PPM
|
|
-bmp ......... save as uncompressed BMP format
|
|
-tiff ........ save as uncompressed TIFF format
|
|
-pgm ......... save the raw YUV samples as a grayscale PGM
|
|
file with IMC4 layout
|
|
-yuv ......... save the raw YUV samples in flat layout
|
|
```
|
|
|
|
Other options are:
|
|
|
|
```
|
|
-version ..... print version number and exit
|
|
-nofancy ..... don't use the fancy YUV420 upscaler
|
|
-nofilter .... disable in-loop filtering
|
|
-nodither .... disable dithering
|
|
-dither <d> .. dithering strength (in 0..100)
|
|
-alpha_dither use alpha-plane dithering if needed
|
|
-mt .......... use multi-threading
|
|
-crop <x> <y> <w> <h> ... crop output with the given rectangle
|
|
-resize <w> <h> ......... resize output (*after* any cropping)
|
|
-flip ........ flip the output vertically
|
|
-alpha ....... only save the alpha plane
|
|
-incremental . use incremental decoding (useful for tests)
|
|
-h ........... this help message
|
|
-v ........... verbose (e.g. print encoding/decoding times)
|
|
-quiet ....... quiet mode, don't print anything
|
|
-noasm ....... disable all assembly optimizations
|
|
```
|
|
|
|
## WebP file analysis tool
|
|
|
|
`webpinfo` can be used to print out the chunk level structure and bitstream
|
|
header information of WebP files. It can also check if the files are of valid
|
|
WebP format.
|
|
|
|
Usage:
|
|
|
|
```shell
|
|
webpinfo [options] in_files
|
|
```
|
|
|
|
Note: there could be multiple input files; options must come before input files.
|
|
|
|
Options:
|
|
|
|
```
|
|
-version ........... Print version number and exit.
|
|
-quiet ............. Do not show chunk parsing information.
|
|
-diag .............. Show parsing error diagnosis.
|
|
-summary ........... Show chunk stats summary.
|
|
-bitstream_info .... Parse bitstream header.
|
|
```
|
|
|
|
## Visualization tool
|
|
|
|
There's a little self-serve visualization tool called 'vwebp' under the
|
|
examples/ directory. It uses OpenGL to open a simple drawing window and show a
|
|
decoded WebP file. It's not yet integrated in the automake build system, but you
|
|
can try to manually compile it using the recommendations below.
|
|
|
|
Usage:
|
|
|
|
```shell
|
|
vwebp in_file [options]
|
|
```
|
|
|
|
Decodes the WebP image file and visualize it using OpenGL
|
|
|
|
Options are:
|
|
|
|
```
|
|
-version ..... print version number and exit
|
|
-noicc ....... don't use the icc profile if present
|
|
-nofancy ..... don't use the fancy YUV420 upscaler
|
|
-nofilter .... disable in-loop filtering
|
|
-dither <int> dithering strength (0..100), default=50
|
|
-noalphadither disable alpha plane dithering
|
|
-usebgcolor .. display background color
|
|
-mt .......... use multi-threading
|
|
-info ........ print info
|
|
-h ........... this help message
|
|
```
|
|
|
|
Keyboard shortcuts:
|
|
|
|
```
|
|
'c' ................ toggle use of color profile
|
|
'b' ................ toggle background color display
|
|
'i' ................ overlay file information
|
|
'd' ................ disable blending & disposal (debug)
|
|
'q' / 'Q' / ESC .... quit
|
|
```
|
|
|
|
### Building
|
|
|
|
Prerequisites:
|
|
|
|
1. OpenGL & OpenGL Utility Toolkit (GLUT)
|
|
|
|
Linux: `sudo apt-get install freeglut3-dev mesa-common-dev`
|
|
|
|
Mac + Xcode: These libraries should be available in the OpenGL / GLUT
|
|
frameworks.
|
|
|
|
Windows: http://freeglut.sourceforge.net/index.php#download
|
|
|
|
2. (Optional) qcms (Quick Color Management System)
|
|
|
|
1. Download qcms from Mozilla / Chromium:
|
|
https://hg.mozilla.org/mozilla-central/file/0e7639e3bdfb/gfx/qcms
|
|
https://source.chromium.org/chromium/chromium/src/+/main:third_party/qcms/;drc=d4a2f8e1ed461d8fc05ed88d1ae2dc94c9773825
|
|
2. Build and archive the source files as libqcms.a / qcms.lib
|
|
3. Update makefile.unix / Makefile.vc
|
|
1. Define WEBP_HAVE_QCMS
|
|
2. Update include / library paths to reference the qcms directory.
|
|
|
|
Build using makefile.unix / Makefile.vc:
|
|
|
|
```shell
|
|
$ make -f makefile.unix examples/vwebp
|
|
> nmake /f Makefile.vc CFG=release-static \
|
|
../obj/x64/release-static/bin/vwebp.exe
|
|
```
|
|
|
|
## Animation creation tool
|
|
|
|
The utility `img2webp` can turn a sequence of input images (PNG, JPEG, ...) into
|
|
an animated WebP file. It offers fine control over duration, encoding modes,
|
|
etc.
|
|
|
|
Usage:
|
|
|
|
```shell
|
|
img2webp [file_options] [[frame_options] frame_file]... [-o webp_file]
|
|
```
|
|
|
|
File-level options (only used at the start of compression):
|
|
|
|
```
|
|
-min_size ............ minimize size
|
|
-kmax <int> .......... maximum number of frame between key-frames
|
|
(0=only keyframes)
|
|
-kmin <int> .......... minimum number of frame between key-frames
|
|
(0=disable key-frames altogether)
|
|
-mixed ............... use mixed lossy/lossless automatic mode
|
|
-near_lossless <int> . use near-lossless image preprocessing
|
|
(0..100=off), default=100
|
|
-sharp_yuv ........... use sharper (and slower) RGB->YUV conversion
|
|
(lossy only)
|
|
-loop <int> .......... loop count (default: 0, = infinite loop)
|
|
-v ................... verbose mode
|
|
-h ................... this help
|
|
-version ............. print version number and exit
|
|
```
|
|
|
|
Per-frame options (only used for subsequent images input):
|
|
|
|
```
|
|
-d <int> ............. frame duration in ms (default: 100)
|
|
-lossless ........... use lossless mode (default)
|
|
-lossy ... ........... use lossy mode
|
|
-q <float> ........... quality
|
|
-m <int> ............. method to use
|
|
```
|
|
|
|
example: `img2webp -loop 2 in0.png -lossy in1.jpg -d 80 in2.tiff -o out.webp`
|
|
|
|
Note: if a single file name is passed as the argument, the arguments will be
|
|
tokenized from this file. The file name must not start with the character '-'.
|
|
|
|
## Animated GIF conversion
|
|
|
|
Animated GIF files can be converted to WebP files with animation using the
|
|
gif2webp utility available under examples/. The files can then be viewed using
|
|
vwebp.
|
|
|
|
Usage:
|
|
|
|
```shell
|
|
gif2webp [options] gif_file -o webp_file
|
|
```
|
|
|
|
Options:
|
|
|
|
```
|
|
-h / -help ............. this help
|
|
-lossy ................. encode image using lossy compression
|
|
-mixed ................. for each frame in the image, pick lossy
|
|
or lossless compression heuristically
|
|
-q <float> ............. quality factor (0:small..100:big)
|
|
-m <int> ............... compression method (0=fast, 6=slowest)
|
|
-min_size .............. minimize output size (default:off)
|
|
lossless compression by default; can be
|
|
combined with -q, -m, -lossy or -mixed
|
|
options
|
|
-kmin <int> ............ min distance between key frames
|
|
-kmax <int> ............ max distance between key frames
|
|
-f <int> ............... filter strength (0=off..100)
|
|
-metadata <string> ..... comma separated list of metadata to
|
|
copy from the input to the output if present
|
|
Valid values: all, none, icc, xmp (default)
|
|
-loop_compatibility .... use compatibility mode for Chrome
|
|
version prior to M62 (inclusive)
|
|
-mt .................... use multi-threading if available
|
|
|
|
-version ............... print version number and exit
|
|
-v ..................... verbose
|
|
-quiet ................. don't print anything
|
|
```
|
|
|
|
### Building
|
|
|
|
With the libgif development files installed, gif2webp can be built using
|
|
makefile.unix:
|
|
|
|
```shell
|
|
$ make -f makefile.unix examples/gif2webp
|
|
```
|
|
|
|
or using autoconf:
|
|
|
|
```shell
|
|
$ ./configure --enable-everything
|
|
$ make
|
|
```
|
|
|
|
## Comparison of animated images
|
|
|
|
Test utility anim_diff under examples/ can be used to compare two animated
|
|
images (each can be GIF or WebP).
|
|
|
|
Usage:
|
|
|
|
```shell
|
|
anim_diff <image1> <image2> [options]
|
|
```
|
|
|
|
Options:
|
|
|
|
```
|
|
-dump_frames <folder> dump decoded frames in PAM format
|
|
-min_psnr <float> ... minimum per-frame PSNR
|
|
-raw_comparison ..... if this flag is not used, RGB is
|
|
premultiplied before comparison
|
|
-max_diff <int> ..... maximum allowed difference per channel
|
|
between corresponding pixels in subsequent
|
|
frames
|
|
-h .................. this help
|
|
-version ............ print version number and exit
|
|
```
|
|
|
|
### Building
|
|
|
|
With the libgif development files installed, anim_diff can be built using
|
|
makefile.unix:
|
|
|
|
```shell
|
|
$ make -f makefile.unix examples/anim_diff
|
|
```
|
|
|
|
or using autoconf:
|
|
|
|
```shell
|
|
$ ./configure --enable-everything
|
|
$ make
|
|
```
|
|
|
|
## WebP Mux tool
|
|
|
|
The examples/ directory contains a tool (webpmux) for manipulating WebP files.
|
|
The webpmux tool can be used to create an extended format WebP file and also to
|
|
extract or strip relevant data from such a file.
|
|
|
|
A list of options is available using the -help command line flag:
|
|
|
|
```shell
|
|
> webpmux -help
|
|
Usage: webpmux -get GET_OPTIONS INPUT -o OUTPUT
|
|
webpmux -set SET_OPTIONS INPUT -o OUTPUT
|
|
webpmux -duration DURATION_OPTIONS [-duration ...]
|
|
INPUT -o OUTPUT
|
|
webpmux -strip STRIP_OPTIONS INPUT -o OUTPUT
|
|
webpmux -frame FRAME_OPTIONS [-frame...] [-loop LOOP_COUNT]
|
|
[-bgcolor BACKGROUND_COLOR] -o OUTPUT
|
|
webpmux -info INPUT
|
|
webpmux [-h|-help]
|
|
webpmux -version
|
|
webpmux argument_file_name
|
|
|
|
GET_OPTIONS:
|
|
Extract relevant data:
|
|
icc get ICC profile
|
|
exif get EXIF metadata
|
|
xmp get XMP metadata
|
|
frame n get nth frame
|
|
|
|
SET_OPTIONS:
|
|
Set color profile/metadata/parameters:
|
|
loop LOOP_COUNT set the loop count
|
|
bgcolor BACKGROUND_COLOR set the animation background color
|
|
icc file.icc set ICC profile
|
|
exif file.exif set EXIF metadata
|
|
xmp file.xmp set XMP metadata
|
|
where: 'file.icc' contains the ICC profile to be set,
|
|
'file.exif' contains the EXIF metadata to be set
|
|
'file.xmp' contains the XMP metadata to be set
|
|
|
|
DURATION_OPTIONS:
|
|
Set duration of selected frames:
|
|
duration set duration for all frames
|
|
duration,frame set duration of a particular frame
|
|
duration,start,end set duration of frames in the
|
|
interval [start,end])
|
|
where: 'duration' is the duration in milliseconds
|
|
'start' is the start frame index
|
|
'end' is the inclusive end frame index
|
|
The special 'end' value '0' means: last frame.
|
|
|
|
STRIP_OPTIONS:
|
|
Strip color profile/metadata:
|
|
icc strip ICC profile
|
|
exif strip EXIF metadata
|
|
xmp strip XMP metadata
|
|
|
|
FRAME_OPTIONS(i):
|
|
Create animation:
|
|
file_i +di[+xi+yi[+mi[bi]]]
|
|
where: 'file_i' is the i'th animation frame (WebP format),
|
|
'di' is the pause duration before next frame,
|
|
'xi','yi' specify the image offset for this frame,
|
|
'mi' is the dispose method for this frame (0 or 1),
|
|
'bi' is the blending method for this frame (+b or -b)
|
|
|
|
LOOP_COUNT:
|
|
Number of times to repeat the animation.
|
|
Valid range is 0 to 65535 [Default: 0 (infinite)].
|
|
|
|
BACKGROUND_COLOR:
|
|
Background color of the canvas.
|
|
A,R,G,B
|
|
where: 'A', 'R', 'G' and 'B' are integers in the range 0 to 255 specifying
|
|
the Alpha, Red, Green and Blue component values respectively
|
|
[Default: 255,255,255,255]
|
|
|
|
INPUT & OUTPUT are in WebP format.
|
|
|
|
Note: The nature of EXIF, XMP and ICC data is not checked and is assumed to be
|
|
valid.
|
|
|
|
Note: if a single file name is passed as the argument, the arguments will be
|
|
tokenized from this file. The file name must not start with the character '-'.
|
|
```
|