-
Notifications
You must be signed in to change notification settings - Fork 0
/
README.mux
185 lines (148 loc) · 6.27 KB
/
README.mux
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
__ __ ____ ____ ____ __ __ _ __ __
/ \\/ \/ _ \/ _ \/ _ \/ \ \/ \___/_ / _\
\ / __/ _ \ __/ / / (_/ /__
\__\__/\_____/_____/__/ \__//_/\_____/__/___/v0.1.1
Description:
============
WebPMux: set of two libraries 'Mux' and 'Demux' for creation, extraction and
manipulation of an extended format WebP file, which can have features like
color profile, metadata and animation. Reference command-line tools 'webpmux'
and 'vwebp' as well as the WebP container specification
'doc/webp-container-spec.txt' are also provided in this package.
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:
> webpmux -help
Usage: webpmux -get GET_OPTIONS INPUT -o OUTPUT
webpmux -set SET_OPTIONS 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
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.
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
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
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).
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.
Visualization tool:
===================
The examples/ directory also contains a tool (vwebp) for viewing WebP files.
It decodes the image and visualizes it using OpenGL. See the libwebp README
for details on building and running this program.
Mux API:
========
The Mux API contains methods for adding data to and reading data from WebP
files. This API currently supports XMP/EXIF metadata, ICC profile and animation.
Other features may be added in subsequent releases.
Example#1 (pseudo code): Creating a WebPMux object with image data, color
profile and XMP metadata.
int copy_data = 0;
WebPMux* mux = WebPMuxNew();
// ... (Prepare image data).
WebPMuxSetImage(mux, &image, copy_data);
// ... (Prepare ICC profile data).
WebPMuxSetChunk(mux, "ICCP", &icc_profile, copy_data);
// ... (Prepare XMP metadata).
WebPMuxSetChunk(mux, "XMP ", &xmp, copy_data);
// Get data from mux in WebP RIFF format.
WebPMuxAssemble(mux, &output_data);
WebPMuxDelete(mux);
// ... (Consume output_data; e.g. write output_data.bytes to file).
WebPDataClear(&output_data);
Example#2 (pseudo code): Get image and color profile data from a WebP file.
int copy_data = 0;
// ... (Read data from file).
WebPMux* mux = WebPMuxCreate(&data, copy_data);
WebPMuxGetFrame(mux, 1, &image);
// ... (Consume image; e.g. call WebPDecode() to decode the data).
WebPMuxGetChunk(mux, "ICCP", &icc_profile);
// ... (Consume icc_profile).
WebPMuxDelete(mux);
free(data);
For a detailed Mux API reference, please refer to the header file
(src/webp/mux.h).
Demux API:
==========
The Demux API enables extraction of images and extended format data from
WebP files. This API currently supports reading of XMP/EXIF metadata, ICC
profile and animated images. Other features may be added in subsequent
releases.
Code Example: Demuxing WebP data to extract all the frames, ICC profile
and EXIF/XMP metadata.
WebPDemuxer* demux = WebPDemux(&webp_data);
uint32_t width = WebPDemuxGetI(demux, WEBP_FF_CANVAS_WIDTH);
uint32_t height = WebPDemuxGetI(demux, WEBP_FF_CANVAS_HEIGHT);
// ... (Get information about the features present in the WebP file).
uint32_t flags = WebPDemuxGetI(demux, WEBP_FF_FORMAT_FLAGS);
// ... (Iterate over all frames).
WebPIterator iter;
if (WebPDemuxGetFrame(demux, 1, &iter)) {
do {
// ... (Consume 'iter'; e.g. Decode 'iter.fragment' with WebPDecode(),
// ... and get other frame properties like width, height, offsets etc.
// ... see 'struct WebPIterator' below for more info).
} while (WebPDemuxNextFrame(&iter));
WebPDemuxReleaseIterator(&iter);
}
// ... (Extract metadata).
WebPChunkIterator chunk_iter;
if (flags & ICCP_FLAG) WebPDemuxGetChunk(demux, "ICCP", 1, &chunk_iter);
// ... (Consume the ICC profile in 'chunk_iter.chunk').
WebPDemuxReleaseChunkIterator(&chunk_iter);
if (flags & EXIF_FLAG) WebPDemuxGetChunk(demux, "EXIF", 1, &chunk_iter);
// ... (Consume the EXIF metadata in 'chunk_iter.chunk').
WebPDemuxReleaseChunkIterator(&chunk_iter);
if (flags & XMP_FLAG) WebPDemuxGetChunk(demux, "XMP ", 1, &chunk_iter);
// ... (Consume the XMP metadata in 'chunk_iter.chunk').
WebPDemuxReleaseChunkIterator(&chunk_iter);
WebPDemuxDelete(demux);
For a detailed Demux API reference, please refer to the header file
(src/webp/demux.h).
Bugs:
=====
Please report all bugs to our issue tracker:
http://code.google.com/p/webp/issues
Patches welcome! See this page to get started:
http://www.webmproject.org/code/contribute/submitting-patches/
Discuss:
========
Email: webp-discuss@webmproject.org
Web: http://groups.google.com/a/webmproject.org/group/webp-discuss