dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-12-27 06:08:21 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Ordering of description of bits in container spec

Browse Source 
The description of bits in a byte should be from MSB to LSB

Change-Id: I50f2dfbb79b33eb434a771cca252c5d0f81fc71e
This commit is contained in:
Urvang Joshi 2012-11-02 15:27:37 -07:00
parent d57357762a
commit 391f9db9fa
1 changed files with 26 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
doc/webp-container-spec.txt
View File

@ -13,7 +13,7 @@ end of this file.
WebP Container Specification WebP Container Specification
============================ ============================
_Working Draft, v0.7, 20121101_ _Working Draft, v0.7, 20121102_
* TOC placeholder * TOC placeholder
@ -291,28 +291,28 @@ Extended WebP file header:
... Canvas Height Minus One | ... Canvas Height Minus One |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved (R): 2 bits Reserved (Rsv): 2 bits
: SHOULD be `0`. : SHOULD be `0`.
XMP metadata (X): 1 bit ICC profile (I): 1 bit
: Set if the file contains XMP metadata. : Set if the file contains an ICC profile.
EXIF metadata (E): 1 bit
: Set if the file contains EXIF metadata.
Alpha (L): 1 bit Alpha (L): 1 bit
: Set if the file contains some (or all) images with transparency information : Set if the file contains some (or all) images with transparency information
("alpha"). ("alpha").
ICC profile (I): 1 bit EXIF metadata (E): 1 bit
: Set if the file contains an ICC profile. : Set if the file contains EXIF metadata.
Reserved (Rsv): 2 bits XMP metadata (X): 1 bit
: Set if the file contains XMP metadata.
Reserved (R): 2 bits
: SHOULD be `0`. : SHOULD be `0`.
@ -346,12 +346,18 @@ Future specifications MAY add more fields.
|Rsv| P | F | C | Alpha Bitstream... | |Rsv| P | F | C | Alpha Bitstream... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Compression method (C): 2 bits Reserved (Rsv): 2 bits
: The compression method used: : SHOULD be `0`.
* `0`: No compression. Pre-processing (P): 2 bits
* `1`: Compressed using the WebP lossless format.
: These INFORMATIVE bits are used to signal the pre-processing that has
been performed during compression. The decoder can use this information to
e.g. dither the values or smooth the gradients prior to display.
* `0`: no pre-processing
* `1`: level reduction
Filtering method (F): 2 bits Filtering method (F): 2 bits
@ -398,20 +404,14 @@ There are special cases for left-most and top-most pixel positions:
location (x, 0) are predicted using the location (x-1, 0) on the left. location (x, 0) are predicted using the location (x-1, 0) on the left.
Pre-processing (P): 2 bits
: These INFORMATIVE bits are used to signal the pre-processing that has
been performed during compression. The decoder can use this information to
e.g. dither the values or smooth the gradients prior to display.
* `0`: no pre-processing
* `1`: level reduction
Decoders are not required to use this information in any specified way. Decoders are not required to use this information in any specified way.
Reserved (Rsv): 2 bits Compression method (C): 2 bits
: SHOULD be `0`. : The compression method used:
* `0`: No compression.
* `1`: Compressed using the WebP lossless format.
Alpha bitstream: _Chunk Size_ - `1` bytes Alpha bitstream: _Chunk Size_ - `1` bytes