Commit Graph

181 Commits

Author SHA1 Message Date
James Zern
84628e5611 webp-lossless-bitstream-spec: clarify image width changes
After processing the Color Indexing Transform the image width is
subsampled by the transform's width_bits.

Bug: webp:611
Change-Id: If8d2d47dbe05e5c8085fb3fb4c1b63552be9028b
2023-07-20 17:54:20 -07:00
James Zern
982c177c8a webp-lossless-bitstream-spec: fix struct member refs
remove trailing '_' to match the definition of ColorTransformElement

Bug: webp:611
Change-Id: I741213b389fc88473c72c64090a4733f51d87925
2023-07-14 15:13:27 -07:00
James Zern
56cf562570 webp-lossless-bitstream-spec: use RFC 7405 for ABNF
This allows for case sensitive literals.

Bug: webp:611
Change-Id: I5258c67ab12c48593d433449328fd85d461a05d2
2023-07-14 15:13:27 -07:00
James Zern
6c6b3fd317 webp-lossless-bitstream-spec,cosmetics: delete blank lines
This normalizes the spacing between sections and quiets some lint
warnings.

Bug: webp:611
Change-Id: Ic36eb08d55a566def74f746e2ec225c67ff8aecf
2023-07-14 15:12:35 -07:00
James Zern
e4fc2f78c7 webp-lossless-bitstream-spec: add validity note for max_symbol
Bug: webp:611
Change-Id: Id56ca4fd0ad3cfc17c9c971281ccfb8ce7eaa2f4
2023-07-07 15:54:34 -07:00
James Zern
71916726b6 webp-lossless-bitstream-spec: fix max_symbol definition
If ReadBits(0) == 0, the value of max_symbol is set to the alphabet size
for each symbol type.

See vp8l_dec.c, ReadHuffmanCode(), which passes alphabet_size to
ReadHuffmanCodeLengths() as num_symbols, and ReadHuffmanCodeLengths()
then sets max_symbol to that.

Bug: webp:611
Change-Id: I662bd1d7f372e7f2e9c71cc86f87aefd02f36647
2023-07-07 15:54:34 -07:00
James Zern
4298e9765c webp-lossless-bitstream-spec: add PredictorTransformOutput
Describe the addition of the residual value to the predicted value.

Bug: webp:611
Change-Id: Id0300937eeebbafec3b2cd15376c56418c98a3bf
2023-06-26 12:51:36 -07:00
James Zern
cd7e02bece webp-lossless-bitstream-spec: fix RIFF-header ABNF
0x2f is a part of the image header, not RIFF header

Bug: webp:611
Change-Id: I5dba5ccfebeb25586723a1f3e00eebc317806928
2023-06-26 12:51:36 -07:00
James Zern
6c3845f9e0 webp-lossless-bitstream-spec: split LZ77 Backward Ref section
Make Distance Mapping its section for ease of reference.

Bug: webp:611
Change-Id: I57bb68e0fcf4d23ce0013f327adce93c6377be3a
2023-06-26 12:51:36 -07:00
James Zern
7f1b6799db webp-lossless-bitstream-spec: split Meta Prefix Codes section
Make Entropy Image and Interpretation of Meta Prefix Codes their own
section for ease of reference.

Bug: webp:611
Change-Id: I2dba7b4efd02d8bb250810ebff42ac1687262804
2023-06-26 12:51:36 -07:00
James Zern
7b634d8f0c webp-lossless-bitstream-spec: note transform order
transforms are applied in reverse bitstream order.

Bug: webp:611
Change-Id: I172aca36bbd5c3358a71b0acb49c5704ceee63d7
2023-06-26 12:51:36 -07:00
James Zern
6d6d4915ce webp-lossless-bitstream-spec: update transformations text
follow up to:
29c9f2d4 webp-lossless-bitstream-spec: minor wording updates

Universally use 'transform' over 'transformation'. The doc generally
uses 'transform' to talk about the individual transforms themselves as
well as their related data.

Bug: webp:611
Change-Id: I097701873bbc440bd399ab5440a914a14f7c62f6
2023-06-26 12:50:39 -07:00
James Zern
08d60d6006 webp-lossless-bitstream-spec: split code length section
Make Simple / Normal Code Length Code their own section for ease of
reference.

Bug: webp:611
Change-Id: I1e6ed50d98f9258cacb163d2059716b5356e8b6f
2023-06-21 19:20:12 -07:00
James Zern
7a12afcc54 webp-lossless-bitstream-spec: rm unused anchor
The last use of #decoding-the-code-lengths was removed in:
86f94ee0 Update lossless spec with Huffman codes.

Also remove the redundant section header associated with it.

Bug: webp:611
Change-Id: I7f6bb1a1b75255324f185f4591313d9e6d49d1e9
2023-06-21 19:16:39 -07:00
James Zern
14a9dbfba0 webp-lossless-bitstream-spec: refine single node text
Remove the ambiguous 'should' which in other contexts might result in
questions as to whether it is a SHOULD or a MUST.

Change-Id: I9b396187ebde5ea5a0dbaf42daee6acf541258cd
2023-06-20 19:30:20 -07:00
James Zern
fe80fbbd6b webp-container-spec: add some missing commas
The serial comma change is based on the Chicago Manual of Style
(CMOS), 17th edition.

Change-Id: I642d6eb87492bb671869b25415c59b96b749c798
2023-06-12 22:03:01 -07:00
James Zern
03a7a04892 webp-lossless-bitstream-spec: rm redundant statement
Within the 'Entropy image' subsection, its clear this is what is being
described in the following paragraphs. Remove 'as described below' from
the first sentence.

Bug: webp:611
Change-Id: I365d69c8f6963cd826849ebdd96e46206d38b55d
2023-06-08 11:22:10 -07:00
James Zern
c437c7aace webp-lossless-bitstream-spec: mv up prefix code group def
Move this to the top-level of the "Details" section as prefix codes are
discussed in both "Decoding and Building the Prefix Codes" and "Decoding
of Meta Prefix Codes"

Bug: webp:611
Change-Id: Ide2dfedf081d6c94122ac16ecded968ed760f90c
2023-06-08 11:22:10 -07:00
James Zern
e4f17a31a7 webp-lossless-bitstream-spec: fix section reference
in the Transformations section describing decoding of the transform
data followed by the image data. The section numbers were adjusted by 1
in:
337cf69f webp-lossless-bitstream-spec: mv Nomenclature after Intro

Bug: webp:611
Change-Id: I4eede0d068fabdef51a140a0268436ab6629e8bb
2023-06-08 11:22:10 -07:00
James Zern
e2ecd5e937 webp-lossless-bitstream-spec: clarify ABNF syntax
Give some examples of repetition and binary value notation to limit the
need to follow the ABNF reference.

Bug: webp:611
Change-Id: I5b5a7632f011e1523b4a528653fe3630afba3e3e
2023-06-08 11:22:10 -07:00
James Zern
8b55425a56 webp-lossless-bitstream-spec: refine pixel copy text
in 6.2.3 Decoding Entropy-Coded Image Data.

The copying of distance code pixels cause some confusion during the
AUTH48 portion of the RFC review process.

Bug: webp:611
Change-Id: I78f547ae10c95f180355a4c93ec6d48acdc09141
2023-06-08 11:22:10 -07:00
James Zern
29c9f2d410 webp-lossless-bitstream-spec: minor wording updates
Mostly grammatical and addition/subtraction of commas from the AUTH48
portion of the RFC review process.

The serial comma changes are based on the Chicago Manual of Style
(CMOS), 17th edition.

Bug: webp:611
Change-Id: I5ae2d1cc0196009dbf3a4c2195cc73c2ef809b49
2023-06-08 11:21:55 -07:00
James Zern
7f75c91ced webp-container-spec: fix location of informative msg
preprocessing bits are informative, not the filtering bits.

since:
391f9db9 Ordering of description of bits in container spec

Change-Id: I1c0da963074ce9cf4d33a13b4b36c9421b3e3b9d
2023-06-06 22:09:41 -07:00
James Zern
f6499943c4 webp-container-spec: consistently quote FourCCs
from the AUTH48 portion of the RFC review process

Change-Id: I3aad4b32c95517735e98ffa0120228ee24be6a4d
2023-06-06 18:47:20 -07:00
James Zern
49918af32b webp-container-spec: minor wording updates
Mostly grammatical and addition/subtraction of commas from the AUTH48
portion of the RFC review process.

The serial comma changes are based on the Chicago Manual of Style
(CMOS), 17th edition.

Change-Id: Ic75abf2e53e09c8a849e28e9c40e16c127515287
2023-06-05 18:26:34 -07:00
James Zern
15b365083d doc/webp-container-spec: rm future codec comment
From the compression standpoint the file format is fixed at this point.

Change-Id: I788fcf7106e4840bf2f9950dfb099a7bab88b3bf
2023-05-26 15:48:31 -07:00
James Zern
c369c4bf0b doc/webp-lossless-bitstream-spec: improve link text
Reference the section by number, rather than 'this section'. Fixes a
lint warning:

Style notice: Write unique, descriptive link text that makes sense
without the surrounding text. Don't use phrases such as this document,
this article, or click here.
https://developers.google.com/style/link-text?hl=en#write-link-text

Change-Id: Iab33e4980528dddb5eed4404d25a4a746705131a
2023-05-26 15:48:28 -07:00
James Zern
1de35f476b doc/webp-container-spec: don't use 'currently'
Provide examples of formats that WebP performs better than.

https://developers.google.com/style/timeless-documentation

Change-Id: I4ead60be349d8650478788484989bde9ff18f6b6
2023-05-26 15:48:26 -07:00
James Zern
bb06a16ed1 doc/webp-container-spec: prefer present tense
https://developers.google.com/style/tense

Change-Id: I0cd4e1431cddc340adf5634c07f0c60635b3d4f2
2023-05-26 15:48:23 -07:00
James Zern
9f38b71e01 doc/webp-lossless-bitstream-spec: prefer present tense
https://developers.google.com/style/tense

Change-Id: I1151ad0f585afd388920e6910a30aca4c2d0cc32
2023-05-26 15:48:17 -07:00
James Zern
7acb6b829a doc/webp-container-spec: avoid i.e. & e.g.
Using 'that is' or 'for example' is recommended:
https://developers.google.com/style/abbreviations#dont-use

Change-Id: I25b45f5b41687dfbd25a0fbea4978d6bc8e44ad2
2023-05-26 15:48:12 -07:00
James Zern
4967e7cd78 doc/webp-lossless-bitstream-spec: avoid i.e. & e.g.
Using 'that is' or 'for example' is recommended:
https://developers.google.com/style/abbreviations#dont-use

Change-Id: I5d0dad2ee7ae5ebaf73661d5d79a4a2f1dc1802a
2023-05-26 15:48:09 -07:00
Jyrki Alakuijala
428588ef90 clarify single leaf node trees and use of canonical prefix coding
remove AMENDED-notes (the last functional spec change to match with the
implementation is from 2014, other amendments are clarifications)

Bug: webp:581
Change-Id: Ic47739be0fd5a975fd734d6813567ca615304f1d
2023-05-25 17:25:48 -07:00
James Zern
17e0ef1da5 webp-lossless-bitstream-spec: remove use of 'dynamics'
when bit width or precision are meant.

Change-Id: I89c2279e99b02c3e8a3bf39860364d2ce6d909c8
2023-05-12 15:10:30 -07:00
James Zern
84d04c4845 webp-lossless-bitstream-spec: add missing bits to ABNF
alpha-is-used and the version number were missing before 'image-stream'

spotted by thakis@

Change-Id: I7a4f1d2e0f0962bb1a79a0400c229738159d88a5
2023-04-13 12:13:34 -07:00
James Zern
4c3d7018c0 webp-lossless-bitstream-spec: condense normal-prefix-code
Have this match simple-prefix-code and redirect to "Normal Code Length
Code" as the added indirection to 'code-length-code' and the undefined
'encoded-code-lengths' doesn't add much.

spotted by thakis@

Change-Id: Icd6b64a47c4e0001e93271d9ae5585be4a6d5906
2023-04-10 17:22:55 -07:00
James Zern
a6a09b3296 webp-lossless-bitstream-spec: fix 2 code typos
- add missing '(' in DIV_ROUND_UP
- in 6.2.2, rename 'pos' variable reference to match definition
  ('position')

spotted by thakis@

Change-Id: Ida3ed281c2c753ebbb0e1eb3c4ed04dadc79ca24
2023-04-10 17:18:52 -07:00
James Zern
2fe27bb96d img2webp: normalize help output
this makes the output from img2webp and the ordering in doc/tools.md and
man/img2webp.1 consistent

Change-Id: Ic389aaa29c20128f2b87f231be383094602f125b
2023-03-17 15:37:55 -07:00
James Zern
24bed3d9fb cwebp: reflow -near_lossless help text
this matches the output from img2webp added in:
0825faa4 img2webp: add -sharp_yuv/-near_lossless

Change-Id: I329ccd796d7e9bee36de1429fceafe83d7dc5532
2023-03-17 15:17:31 -07:00
jzern@google.com
0825faa4c1 img2webp: add -sharp_yuv/-near_lossless
Both are global settings. Modifying them at the frame level is left as a
follow up based on need.

Bug: b/272739498
Change-Id: If15256c052f73fe3df56be5e0095e76d9870cc0f
2023-03-17 09:35:29 -07:00
James Zern
d3e151fc03 doc/api.md,webp_js/README.md: Webp -> WebP
Change-Id: Ib30d008b5750d2e4064aaf478db6f5bc7aa5902e
2022-12-15 18:14:19 -08:00
James Zern
e5fe2cfc1b webp-lossless-bitstream-spec,cosmetics: reflow paragraphs
Change-Id: Ifd7472fe0678b45efc62faa66de8e8dc2e9931e3
2022-11-22 11:38:01 -08:00
James Zern
0ceeeab987 webp-lossless-bitstream-spec: add amendment note
for fixes to the distance_map pseudo-code, the inverse color transform
description and the num_code_lengths check.

Bug: webp:448
Bug: webp:551
Change-Id: Id7e791b97704dd64bb9519657ce48b92cb457ae4
2022-11-22 11:38:01 -08:00
James Zern
607611cd86 Merge "webp-container-spec: normalize section title case" into main 2022-11-22 19:35:41 +00:00
James Zern
f853685e13 lossless: SUBTRACT_GREEN -> SUBTRACT_GREEN_TRANSFORM
this makes the name of the TransformType enum value match the other
members

Bug: webp:448
Change-Id: I85b2f615f97b40fc6d544197cccfb7189dcf4fc0
2022-11-21 16:48:51 -08:00
James Zern
786497e48a webp-lossless-bitstream-spec: fix inv color txfm description
The prose describing the process was missed in:
44dd765d webp-lossless-bitstream-spec: fix ColorTransform impl

Bug: webp:448
Bug: webp:551
Change-Id: If5fb95103ffedeed113e3ad62510f3a19bfd280e
2022-11-21 16:48:51 -08:00
James Zern
c6ac672dbc webp-lossless-bitstream-spec: fix num_code_lengths check
in the 'Normal Code Length Code' description the number of valid code
lengths is 19, not 18.

Bug: webp:448
Bug: webp:551
Change-Id: Id929604e1d771cb09b2d0ac617e83f21077f21de
2022-11-21 16:48:51 -08:00
James Zern
b5700efb70 webp-lossless-bitstream-spec,cosmetics: grammar/capitalization
Bug: webp:448
Change-Id: I2d6cc66b45342716fdba7792c570510601432109
2022-11-21 16:48:41 -08:00
James Zern
d8ed8c117c webp-container-spec: normalize section title case
Use 'title case' as recommended in RFC 7322 (Section 3.4 Capitalization)

Bug: webp:448
Change-Id: I9762402499eb58acbe9ccb75f4f8d2b9c3e9b26b
2022-11-21 10:53:13 -08:00
James Zern
52ec0b8f61 Merge changes Ie975dbb5,Ifc8c93af,I6ca7c5d6,I2e8d66f5,I152477b8 into main
* changes:
  webp-lossless-bitstream-spec,cosmetics: reflow abstract
  webp-lossless-bitstream-spec: reword abstract re alpha
  webp-lossless-bitstream-spec,cosmetics: normalize range syntax
  webp-lossless-bitstream-spec: limit dist map lut to 69 cols
  webp-lossless-bitstream-spec: fix dist mapping example
2022-11-18 18:28:15 +00:00