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doc/webp-container-spec: light cosmetics

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- provide anchor links to the bitstream chunks referenced in the
  extended format section
- remove some unnecessary parenthetical notation and add some
  consistency to various chunk element definitions

Change-Id: Ifd946fee81b36e4e555399555a2a58c853fdc3b7
This commit is contained in:
James Zern 2012-07-12 19:19:39 -07:00
parent b5e9067a28
commit 20ead3290f
1 changed files with 16 additions and 15 deletions
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31
doc/webp-container-spec.txt
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@ -453,21 +453,21 @@ Frame Y: 24 bits (_uint24_)
Frame Width Minus One: 24 bits (_uint24_) Frame Width Minus One: 24 bits (_uint24_)
: The _1-based_ width of the frame. : The _1-based_ width of the frame.
The Frame Width is '1 + Frame Width Minus One' The frame width is '1 + Frame Width Minus One'
Frame Height Minus One: 24 bits (_uint24_) Frame Height Minus One: 24 bits (_uint24_)
: The _1-based_ height of the frame. : The _1-based_ height of the frame.
The Frame Height is '1 + Frame Height Minus One' The frame height is '1 + Frame Height Minus One'
Frame Duration Minus One: 24 bits (_uint24_) Frame Duration Minus One: 24 bits (_uint24_)
: _1-based_ time to wait before displaying the next frame, in 1 millisecond : The _1-based_ time to wait before displaying the next frame, in 1 millisecond
units. The actual duration is '1 + Frame Duration Minus One' milliseconds. units. The actual duration is '1 + Frame Duration Minus One' milliseconds.
For images that are animations, this chunk contains information about a single For images that are animations, this chunk contains information about a single
frame, and describes the (optional) alpha chunk and the bitstream chunk that frame, and describes the optional alpha chunk and the bitstream chunk that
follows it. If the _Animation flag_ is not set and this chunk is present, follow it. If the _Animation flag_ is not set and this chunk is present,
it SHOULD be ignored. it SHOULD be ignored.
@ -485,14 +485,14 @@ it SHOULD be ignored.
Tile X: 24 bits (_uint24_) Tile X: 24 bits (_uint24_)
: X coordinate of the upper left corner of the tile is `Tile X * 2` : The X coordinate of the upper left corner of the tile is `Tile X * 2`
Tile Y: 24 bits (_uint24_) Tile Y: 24 bits (_uint24_)
: Y coordinate of the upper left corner of the tile is `Tile Y * 2` : The Y coordinate of the upper left corner of the tile is `Tile Y * 2`
For images that contain tiling, this chunk contains information about a single For images that contain tiling, this chunk contains information about a single
tile and describes the (optional) alpha chunk and bitstream chunk that follow tile and describes the optional alpha chunk and the bitstream chunk that follow
it. If the _Tile flag_ is not set and this chunk is present, it SHOULD be it. If the _Tile flag_ is not set and this chunk is present, it SHOULD be
ignored. ignored.
@ -584,17 +584,17 @@ However, a frame/tile containing a 'VP8L' chunk SHOULD NOT contain this chunk.
**Rationale**: the transparency information of a frame/tile is already part of **Rationale**: the transparency information of a frame/tile is already part of
the 'VP8L' chunk. the 'VP8L' chunk.
The alpha channel data is losslessly stored as raw data (when The alpha channel data is stored as uncompressed raw data (when
compression method is '0') or compressed using the lossless format compression method is '0') or compressed using the lossless format
(when the compression method is '1'). (when the compression method is '1').
* Raw data: consists of a byte sequence of length width * height, * Raw data: consists of a byte sequence of length width * height,
containing all the 8bit transparency values in scan order. containing all the 8-bit transparency values in scan order.
* Lossless format compression: the byte sequence is a compressed * Lossless format compression: the byte sequence is a compressed
image-stream (as described in the [WebP Lossless Bitstream Format] image-stream (as described in the [WebP Lossless Bitstream Format]
[webpllspec]) of implicit dimension width x height. (That is, this [webpllspec]) of implicit dimension width x height. That is, this
image-stream does NOT contain any headers describing the image dimension). image-stream does NOT contain any headers describing the image dimension.
**Rationale**: the dimension is already known from other sources, **Rationale**: the dimension is already known from other sources,
so storing it again would be redundant and error-prone. so storing it again would be redundant and error-prone.
@ -605,7 +605,7 @@ compression method is '0') or compressed using the lossless format
of the ARGB quadruplet. of the ARGB quadruplet.
**Rationale**: the green channel is allowed extra transformation **Rationale**: the green channel is allowed extra transformation
steps in the specification -unlike the other channels- that can steps in the specification -- unlike the other channels -- that can
improve compression. improve compression.
#### Bitstream (VP8/VP8L) #### Bitstream (VP8/VP8L)
@ -619,8 +619,9 @@ A bitstream chunk may be either (i) a VP8 chunk, using "VP8 " (note the
significant fourth-character space) as its tag _or_ (ii) a VP8L chunk , using significant fourth-character space) as its tag _or_ (ii) a VP8L chunk , using
"VP8L" as its tag. "VP8L" as its tag.
The formats of VP8 and VP8L chunks are as described in sections _Simple file The formats of VP8 and VP8L chunks are as described in sections
format (lossy)_ and _Simple file format (lossless)_ respectively. [Simple file format (lossy)](#simple-file-format-lossy)
and [Simple file format (lossless)](#simple-file-format-lossless) respectively.
#### Color profile #### Color profile