Babl-0.0.8

Contents

  • Babl
  • News
  • Background
  • How?
  • Features
  • Vocabulary
  •   Data types
  •   Color models
  •   Pixel formats
  • Extensions
  • Dependencies
  • Download
  • CVS
  • Usage
  • Extending
  • Color Management
  • Todo
  • Copyright
  •   Authors

Babl is a dynamic, any to any, pixel format conversion library It
provides conversions between the myriad of buffer types images can be
stored in. Babl doesn't only help with existing pixel formats, but also
facilitates creation of new and uncommon ones.

News

xxxx-xx-xx babl-0.0.2 Green fish release

    DRAFT Initial release.

2005-08-xx babl-0.0.1
    Development release of babl, minimal working configuration for RGB,
    CMYK and YCbCr for 8bit 16bit float and double. Emphasis is on
    precision and clarity of code not speed.

-->

See the ChangeLog in CVS.

Background

When creating various libraries and small tools that deal with computer
graphics I have often created function for converting raster images
between different representations.

Libraries to help with such conversions already do exist, but no
extendable candidate have surfaced in my searches.

The vocabulary developed in babl will most likely be part of GEGL's
vocabulary to describe image buffers.

How babl works

When using BablFishes to do your conversions, you request a fish to
convert between two formats, and an optimal fish to babls capability is
provided that you can use to do your conversions. Babl also provides
the capability to describe new formats based on a vocbulary of user
registered color models and data types.

Babl provides a base vocabulary in BablBase and some extensions thar
are thought to be generally useful.

When performing further extensions to the vocabulary of babl, the
internal consistency is governed by reference conversions that operate
on double (64 bit floating point values.) The only color model created
during BablCore bootstrap is RGBA (linear light RGB, 0.0 - 1.0, with a
linear 0.0 - 1.0 opacity channel.) backed by the double datatype.

If babls conversion isn't fast enough, you can provide your own
conversion shortcut between two formats. The registered shortcut might
also be used by babl as an intermediate conversion when constructing
BablFishes for other conversions.

Babl extensions are shared objects, if you already have developed some
fast conversion functions, wrapping them as babl extensions should not
take much time, and will speed up babl for other users as well you make
the conversions available for others as well.

Features

Core

  • Small API for simple use cases
  • Planar and linear buffers
  • Thread safety for processing.
  • Extendable and introspectable formats, color models, components and
    datatypes
  • Reference 64bit floating point conversions for data types and color
    models.

Vocabulary


+-
Data types
double

bits
    64
bytes
    8

float

bits
    32
bytes
    4

u8

bits
    8
bytes
    1

u8-luma

bits
    8
bytes
    1

u8-chroma

bits
    8
bytes
    1

u16

bits
    16
bytes
    2

u32

bits
    32
bytes
    4

CIE u8 L

bits
    8
bytes
    1

CIE u8 ab

bits
    8
bytes
    1

CIE u16 L

bits
    16
bytes
    2

CIE u16 ab

bits
    16
bytes
    2

Color models
RGBA

components

    R
    G
    B
    A

RGB

components

    R
    G
    B

RaGaBaA

components

    Ra
    Ga
    Ba
    A

R'G'B'

components

    R'
    G'
    B'

R'G'B'A

components

    R'
    G'
    B'
    A

R'aG'aB'aA

components

    R'a
    G'a
    B'a
    A

Y

components

    Y

YA

components

    Y
    A

YaA

components

    Ya
    A

Y'

components

    Y'

Y'A

components

    Y'
    A

Y'aA

components

    Y'a
    A

Y'CbCr

components

    Y'
    Cb
    Cr

Y'CbCrA

components

    Y'
    Cb
    Cr
    A

CIE Lab

components

    CIE L
    CIE a
    CIE b

CIE Lab alpha

components

    CIE L
    CIE a
    CIE b
    A

CMYK

components

    cyan
    magenta
    yellow
    key

Pixel formats
RGBA double

bytes/pixel
    32
model
    RGBA
components

    double  R
    double  G
    double  B
    double  A

R'G'B'A double

bytes/pixel
    32
model
    R'G'B'A
components

    double  R'
    double  G'
    double  B'
    double  A

R'aG'aB'aA double

bytes/pixel
    32
model
    R'aG'aB'aA
components

    double  R'a
    double  G'a
    double  B'a
    double  A

R'G'B' u8

bytes/pixel
    3
model
    R'G'B'
components

    u8 R'
    u8 G'
    u8 B'

R'G'B'A u8

bytes/pixel
    4
model
    R'G'B'A
components

    u8 R'
    u8 G'
    u8 B'
    u8 A

RGBA float

bytes/pixel
    16
model
    RGBA
components

    float  R
    float  G
    float  B
    float  A

RGB float

bytes/pixel
    12
model
    RGB
components

    float  R
    float  G
    float  B

Y'aA double

bytes/pixel
    16
model
    Y'aA
components

    double  Y'a
    double  A

Y double

bytes/pixel
    8
model
    Y
components

    double  Y

YA double

bytes/pixel
    16
model
    YA
components

    double  Y
    double  A

Y'CbCr double

bytes/pixel
    24
model
    Y'CbCr
components

    double  Y'
    double  Cb
    double  Cr

Y'CbCrA double

bytes/pixel
    32
model
    Y'CbCrA
components

    double  Y'
    double  Cb
    double  Cr
    double  A

Y'CbCr u8

bytes/pixel
    3
model
    Y'CbCr
components

    u8-luma    Y'
    u8-chroma  Cb
    u8-chroma  Cr

R'G'B'A float

bytes/pixel
    16
model
    R'G'B'A
components

    float  R'
    float  G'
    float  B'
    float  A

R'G'B'A u16

bytes/pixel
    8
model
    R'G'B'A
components

    u16  R'
    u16  G'
    u16  B'
    u16  A

R'aG'aB'aA float

bytes/pixel
    16
model
    R'aG'aB'aA
components

    float  R'a
    float  G'a
    float  B'a
    float  A

R'aG'aB'aA u16

bytes/pixel
    8
model
    R'aG'aB'aA
components

    u16 R'a
    u16 G'a
    u16 B'a
    u16 A

R'aG'aB'aA u8

bytes/pixel
    4
model
    R'aG'aB'aA
components

    u8 R'a
    u8 G'a
    u8 B'a
    u8 A

R'G'B' float

bytes/pixel
    12
model
    R'G'B'
components

    float  R'
    float  G'
    float  B'

R'G'B' u16

bytes/pixel
    6
model
    R'G'B'
components

    u16  R'
    u16  G'
    u16  B'

Y'A float

bytes/pixel
    8
model
    Y'A
components

    float  Y'
    float  A

Y'aA float

bytes/pixel
    8
model
    Y'aA
components

    float  Y'a
    float  A

Y' float

bytes/pixel
    4
model
    Y'
components

    float  Y'

Y'A u16

bytes/pixel
    4
model
    Y'A
components

    u16  Y'
    u16  A

Y'aA u16

bytes/pixel
    4
model
    Y'aA
components

    u16 Y'a
    u16 A

Y' u16

bytes/pixel
    2
model
    Y'
components

    u16  Y'

Y'A u8

bytes/pixel
    2
model
    Y'A
components

    u8 Y'
    u8 A

Y'aA u8

bytes/pixel
    2
model
    Y'aA
components

    u8 Y'a
    u8 A

Y' u8

bytes/pixel
    1
model
    Y'
components

    u8 Y'

Y'CbCr float

bytes/pixel
    12
model
    Y'CbCr
components

    float  Y'
    float  Cb
    float  Cr

Y'CbCr (Y' as float) (Cb as float) (Cr as float) (A as float)

bytes/pixel
    16
model
    Y'CbCr
components

    float  Y'
    float  Cb
    float  Cr
    float  A

RGBA u16

bytes/pixel
    8
model
    RGBA
components

    u16  R
    u16  G
    u16  B
    u16  A

RGBA u8

bytes/pixel
    4
model
    RGBA
components

    u8  R
    u8  G
    u8  B
    u8  A

RaGaBaA float

bytes/pixel
    16
model
    RaGaBaA
components

    float  Ra
    float  Ga
    float  Ba
    float  A

RaGaBaA u16

bytes/pixel
    8
model
    RaGaBaA
components

    u16  Ra
    u16  Ga
    u16  Ba
    u16  A

RaGaBaA u8

bytes/pixel
    4
model
    RaGaBaA
components

    u8 Ra
    u8 Ga
    u8 Ba
    u8 A

RGB u16

bytes/pixel
    6
model
    RGB
components

    u16  R
    u16  G
    u16  B

RGB u8

bytes/pixel
    3
model
    RGB
components

    u8  R
    u8  G
    u8  B

YA float

bytes/pixel
    8
model
    YA
components

    float  Y
    float  A

YaA float

bytes/pixel
    8
model
    YaA
components

    float  Ya
    float  A

Y float

bytes/pixel
    4
model
    Y
components

    float  Y

YA u16

bytes/pixel
    4
model
    YA
components

    u16  Y
    u16  A

YaA u16

bytes/pixel
    4
model
    YaA
components

    u16  Ya
    u16  A

Y u16

bytes/pixel
    2
model
    Y
components

    u16  Y

YA u8

bytes/pixel
    2
model
    YA
components

    u8  Y
    u8  A

YaA u8

bytes/pixel
    2
model
    YaA
components

    u8 Ya
    u8 A

Y u8

bytes/pixel
    1
model
    Y
components

    u8  Y

Y'CbCrA float

bytes/pixel
    16
model
    Y'CbCrA
components

    float  Y'
    float  Cb
    float  Cr
    float  A

CIE Lab float

bytes/pixel
    12
model
    CIE Lab
components

    float CIE L
    float CIE a
    float CIE b

CIE Lab alpha float

bytes/pixel
    32
model
    CIE Lab alpha
components

    double  CIE L
    double  CIE a
    double  CIE b
    double  A

CIE Lab u8

bytes/pixel
    3
model
    CIE Lab
components

    CIE u8 L   CIE L
    CIE u8 ab  CIE a
    CIE u8 ab  CIE b

CIE Lab u16

bytes/pixel
    6
model
    CIE Lab
components

    CIE u16 L   CIE L
    CIE u16 ab  CIE a
    CIE u16 ab  CIE b

CIE Lab double

bytes/pixel
    24
model
    CIE Lab
components

    double  CIE L
    double  CIE a
    double  CIE b

CIE Lab alpha double

bytes/pixel
    32
model
    CIE Lab alpha
components

    double  CIE L
    double  CIE a
    double  CIE b
    double  A

R'G'B' (B' as u8) (G' as u8) (R' as u8) (PAD as u8)

bytes/pixel
    4
model
    R'G'B'
components

    u8 B'
    u8 G'
    u8 R'
    u8 PAD

CMYK double

bytes/pixel
    32
model
    CMYK
components

    double cyan
    double magenta
    double yellow
    double key

CMYK float

bytes/pixel
    16
model
    CMYK
components

    float cyan
    float yellow
    float magenta
    float key

Extensions

At compile, load and runtime; babl is extendable with:

  • data types.
  • color models.
  • pixel formats.
  • optimized conversion functions:

    SIMD instructions
        MMX, SSE, Altivec ...
    External libraries
        liboil, hermes, libavcodec, lcms, ...

Shortcut coverage

The diagram shown below visualizes the coverage of current shortcut
conversions. A DHTML version is also available.


 ··  ·▁····· ▁   ▂▂                                 ·· · ── 0 RGBA double
· ▁  ▁▂▁▁▁▁▁ · ▂▂▁▁                                 ▁▁ ▁ ── 1 R'G'B'A double
·▁   ▁▂▁▁▁▁▁ ▂                                      ▁▁ ▁ ── 2 R'aG'aB'aA double
    ·        ▁ ▁ ··                                      ── 3 R'G'B' u8
   ·         · ▁▁·▁                                      ── 4 R'G'B'A u8
·▁▁   ·▁▁▁▁▁ ▂                   ·                  ▁▁ ▁ ── 5 RGBA float
▁▂▂  · ▂▂▂▂▂                     ·                  ▂▂ ▂ ── 6 RGB float
·▁▁  ▁▂ ▁▁▁▁ ▂                   ▂                  ▁▁ ▁ ── 7 Y'aA double
·▁▁  ▁▂▁ ▁▁▁ ▂                   ▂                  ▁▁ ▁ ── 8 Y double
·▁▁  ▁▂▁▁ ▁▁ ▂                                      ▁▁ ▁ ── 9 YA double
·▁▁  ▁▂▁▁▁ ▁ ▂                   ▂                  ▁▁ ▁ ──10 Y'CbCr double
·▁▁  ▁▂▁▁▁▁  ▂                                      ▁▁ ▁ ──11 Y'CbCrA double
                                                         ──12 Y'CbCr u8
▁·▂  ▂ ▂▂▂▂▂   ·▁··                                 ▂▂ ▂ ──13 R'G'B'A float
             · ▂▂▁▁                                      ──14 R'G'B'A u16
             ·  ▁·▁                                      ──15 R'aG'aB'aA float
               ▁ ·                                       ──16 R'aG'aB'aA u16
▂▂           ▁ ·· ▂                                      ──17 R'aG'aB'aA u8
▂▁           · ·                                         ──18 R'G'B' float
             ▁ ▁  ·                                      ──19 R'G'B' u16
▂▁           · ▁▂▁▁  ·· ▂  ▁                             ──20 Y'A float
             ▁ ·▂▁▂ · ▁ ▁  ·                             ──21 Y'aA float
 ▂           ▁ ▁  · ··                                   ──22 Y' float
             ▁   ▂▂ · ▁    ▂                             ──23 Y'A u16
               ▁ ▂   ·     ▁                             ──24 Y'aA u16
             ▂ ▂  ▁ ▁▁·                                  ──25 Y' u16
             ▁ ▂ ▂▂ ·▁▁    ▂                             ──26 Y'A u8
             ▂ ▁ ▂  ▁·▂ ·                                ──27 Y'aA u8
             ▂ ▂  ▁ ▁▁·                                  ──28 Y' u8
                                                         ──29 Y'CbCr float
                                                         ──30 Y'CbCr (Y' as float) (Cb as float) (Cr as float) (A as float)
▁▂▂  ·▁▂▂▂▂▂                     ▁                  ▂▂ ▂ ──31 RGBA u16
▁▂▂  ·▁▂▂▂▂▂                         ·              ▂▂ ▂ ──32 RGBA u8
                                                         ──33 RaGaBaA float
                                 ·                       ──34 RaGaBaA u16
                                 ·                       ──35 RaGaBaA u8
▂    ▁·                          ▁                       ──36 RGB u16
▂    ▁▂                         ·▁ ·                     ──37 RGB u8
▁▂▂  ·▁▂▂▂▂▂                     ▁     ··           ▂▂ ▂ ──38 YA float
▂    ▁▂                          ·    · ▁                ──39 YaA float
▂    ▁·                          ▁    ··                 ──40 Y float
     ▁▂                               · ▁                ──41 YA u16
                                 ▁     ·                 ──42 YaA u16
     ▂▁                          ▂    ▁▁·                ──43 Y u16
     ▁▂                               · ▁                ──44 YA u8
     ▂                           ▁    ▁·▂                ──45 YaA u8
     ▂▁                          ▂    ▁▁·                ──46 Y u8
                                                         ──47 Y'CbCrA float
                                                         ──48 CIE Lab float
                                                         ──49 CIE Lab alpha float
                                                         ──50 CIE Lab u8
                                                         ──51 CIE Lab u16
·▁▁  ▁▂▁▁▁▁▁ ▂                   ▂                   ▁ ▁ ──52 CIE Lab double
·▁▁  ▁▂▁▁▁▁▁ ▂                                      ▁  ▁ ──53 CIE Lab alpha double
                                                         ──54 R'G'B' (B' as u8) (G' as u8) (R' as u8) (PAD as u8)
·▁▁  ▁▂▁▁▁▁▁ ▂                   ▂                  ▁▁   ──55 CMYK double
                                                         ──56 CMYK float
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||
||||||||||11111111112222222222333333333344444444445555555
012345678901234567890123456789012345678901234567890123456
total length: 816
total cost  : 1972666

Dependencies

Babl is intended to be a low level infrastructure library and thus
strives for few dependencies and thus portability.

  • libdl (for loading extensions, babl is also reported to work on
    win32)

Download

The latest versioned development version of babl can be found in http:/
/pippin.gimp.org/babl/dist/.

CVS

The latest development version is available in the babl module in GNOME
CVS.

Usage

The simplest scenario for using babl is converting between linear
buffers represented by an existing BablPixelFormat.

babl_process (babl_fish ("srgb", "CIE Lab float"),
              srgb_buffer, lab_buffer,
              pixel_count);

If the existing pixel formats are not sufficient for your conversion
needs, new ones can be created on the fly. The constructor will provide
the prior created one if duplicates are registered.

babl_format_new (babl_model ("R'G'B'"),
                 babl_type ("u8"),
                 babl_component ("B'"),
                 babl_component ("G'"),
                 babl_component ("R'"),
                 NULL);

Extending

For samples of how the current internal api of specification of data
types, color models, and conversions look in the extensions/ directory.
The tables in this HTML file is directly generated based on the data
registered by BablCore (double and RGBA), BablBase (core datatypes, and
RGB models), extensions (CIE Lab, naive CMYK, various shortcut
conversions). The API's used are very similar in style to the API's
described under the Usage section.

Color Management

Babl is not a color management system, since it doesn't deal with ICC
profiles. Babl is designed primarily for internal use when the color
space is already known (sRGB, CIE Lab, Luminance or similar).

It is also possible to register new color models that are managed by a
color management system like lcms, take a look at the lcms-lab
extensions for an example.

TODO

  • Validate that a created BablFishPath is actually faster than the
    BablFishReference it is a replacement for.
  • Compile-time instead of runtime profiling / storage of profiling
    and loss data.. (The speed of conversions is bound to 'wobble',
    according to architecture, compiler flags, concurrently running
    processes and phase of moon.)
  • Horizontal chroma subsampling (4:2:2 and 4:1:1)
  • Thread safety (locking) for mutations of the type system.
  • Support for datatypes that are not a multiple of 8bit.
  • dithering

Copyright

Babl is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

Authors

Øyvind Kolås pippin@gimp.org
    Maintainer and original author.
Sven Neumann sven@gimp.org
    Build enviroment sanity.
Michael Schumacher schumaml@cvs.gnome.org
    win32 support for dynamic extensions.
Kevin Cozens
    Build environment fixes.

/babl-0.0.8
