Contents


babl is a dynamic, any to any, pixel format translation library.

It allows converting between different methods of storing pixels known as pixel formats that have with different bitdepths and other data representations, color models, color spaces and component permutations.

A vocabulary to formulate new pixel formats from existing primitives is provided as well as the framework to add new color models, spaces and data types.

Features

GEGL through GeglBuffer provides tiled buffers with on disk storage as well as linear buffers with accessor functions for efficient data access transparently using babl fishes for translation to the desired pixel formats.

Download

The latest versioned development version of babl can be found in https://download.gimp.org/pub/babl/.

Babl uses git. The main repository is hosted by GNOME. It can be browsed online and cloned with:

git clone git://git.gnome.org/babl

NEWS

The following is a list of the major changes that have gone into each babl release. If there are significant improvements to babl when a GEGL release is done a babl release is most often put out just prior to the GEGL release.

2017-10-03 babl-0.1.32
Added custom primaries and TRC support through ICC parsing, improved float<->half performance, rewrite of all conversions functions to adhere to new signature.
2017-07-15 babl-0.1.30
Thread stability for palette modes, stricter alpha preservation, now cross-compilable on android.
2017-05-30 babl-0.1.28
Fast paths for Lav <-> Lch, release triggered by pending GIMP release.
2017-05-09 babl-0.1.26
Build and install HCY color space, platform independences fixes to fish cache.
2017-02-01 babl-0.1.24
Improvements to profile cache persistance, fast paths that improve actual GIMP use on various precisions, use single precision constants for some more of CIE computions.
2016-11-05 babl-0.1.22
Added cache of profiled conversions, added HCY color model, some precision and performance updated for fast paths.
2016-11-05 babl-0.1.20
Fix run-time errors, leaks, and race conditions. Add conditional fast paths.
2016-06-13 babl-0.1.18
Bugfix: take alpha threshold in consideration when processing floats in SSE2.
2016-02-12 babl-0.1.16
Improvements to half float reference, SIMD, and fast-paths, and CIE float fast paths; cleanups of fast path extensions.
2015-11-19 babl-0.1.14
sRGB precision tuning, stability fixes, locale fix for setting error tolerance.
2015-02-03 babl-0.1.12
optimizations for floating point conversions, HSV and HSL color models, removal of dead code, fixed CIE Lab conversions.
2012-03-30 babl-0.1.10
LUT based speedups for gamma correction / uncorrection.
2012-03-30 babl-0.1.8
Added support for indexed/pallette based formats, constified API.
2011-11-18 babl-0.1.6
Build improvements, remove blatantly wrong conversions from extensions, made it possible to distinguish format_n formats from others, improvements to vala/gobject introspection support.
2011-01-20 babl-0.1.4
Improved cross platform build ability, added code to handle n-component formats, remove extraenous runtime profiling that impacted performance.
2010-01-15 babl-0.1.2
Made babl mostly threadsafe (sufficient for GIMP/GEGLs needs). Streamlined core functionality, reducing number of function calls and removing overeager instrumentation.
2009-05-20 babl-0.1.0
Support for RGBA representation in the frequency domain, un-pre-multiply close-to-zero alpha values to complete black instead of slightly brighter than black, add a BABL_ALPHA_THRESHOLD constant to the API, do a complete overhaul of the babl API and do some changes to increase portability of the library.
2008-06-12 babl-0.0.22
Speed improvements due to: coalesced hashing, early bail out upon creation of duplicate formats, caching of non existing paths. Large amounts of the core has also been reviewed and refactored. Improved conversion coverage in the matrix.
2008-02-27 babl-0.0.20
Builds on OSX Check <0.0 and >1.0 values conversions for accuracy as well.
For more news see git log.

Documentation

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 vocabulary of user registered color models and data types.

Babl provides a base vocabulary in BablBase and some extensions that 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. Defined similarily to scRGB using 64bit floating point.

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 have already 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.

Usage

babl_process (babl_fish (source_format, destination_format),
              source_buffer, destination_buffer,
              pixel_count);

The processing operation that babl performs is copying including conversions if needed between linear buffers containing the same count of pixels, with different pixel formats.

int width = 123, height = 581, pixel_count = width * height;

const Babl *srgb             = babl_format ("R'G'B' u8");
const Babl *lab              = babl_format ("CIE Lab float");
const Babl *srgb_to_lab_fish = babl_fish (srgb, lab);

float         *lab_buffer;
unsigned char *srgb_buffer;

babl_init ();

srgb_buffer = malloc (pixel_count * babl_format_get_bytes_per_pixel (srgb));
lab_buffer  = malloc (pixel_count * 3 * sizeof (float));

...... load data into srgb_buffer .......

babl_process (srgb_to_lab_fish, srgb_buffer, lab_buffer, pixel_count);

...... do operation in lab space ........

babl_process (babl_fish(lab, srgb),
              lab_buffer, srgb_buffer, pixel_count);

/* the data has now been transformed back to srgb data */

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.

const Babl *format = babl_format_new (babl_model ("R'G'B'"),
                                      babl_type ("u16"),
                                      babl_component ("B'"),
                                      babl_component ("G'"),
                                      babl_component ("R'"),
                                      NULL);

Color Management

By default the babl API is assuming data to be (unbounded) sRGB data, data being sRGB defines the conversion to and from gray-scale as well as the gamma - or Transfer Response Curve, TRC, used for converting between linear and non-linear variants of the data.

There is also a babl API call for creating a format for a specific space. babl_format_with_space("R'G'B' u16", babl_space ("Rec2020")) creates a 16 bit integer format for the Rec2020 color space. Babl knows internally about "sRGB", "Rec2020", "Adobe", "Apple" and "ProPhoto" spaces, as they are defined with constants on their wikipedia pages.

Additional spaces can be loaded from monitor-class matrix+TRC ICC v2 and v4 profiles. Using babl_icc_make_space (see babl.h for details). The space of a babl format can also be queried with babl_format_get_space.

The conversions babl does with ICC profiles are according to what is known as the relative-colorimetric intent, monitor profiles containing both the matrices used by babl and 3d CLUTs (color look up tables) most often also do relative-colorimetric transfer for the "perceptual" intent CLUTs, but with a more flexible and possibly higher accuracy conversions. If babl adds support for loading and using CLUTs it will be thus the perceptual intent will by babl be considered a different albeit more accurate relative-colorimetric RGB space.

Vocabulary


+-
bits
64
bytes
8
bits
16
bytes
2
bits
16
bytes
2
bits
32
bytes
4
bits
8
bytes
1
bits
8
bytes
1
bits
8
bytes
1
bits
16
bytes
2
bits
32
bytes
4
bits
8
bytes
1
bits
8
bytes
1
bits
16
bytes
2
bits
16
bytes
2
components
R
G
B
A
components
R
G
B
components
Ra
Ga
Ba
A
components
R'
G'
B'
components
R'
G'
B'
A
components
R'a
G'a
B'a
A
components
Y
components
Y
A
components
Ya
A
components
Y'
components
Y'
A
components
Y'a
A
components
Y'
Cb
Cr
components
Y'
Cb
Cr
A
components
CIE L
CIE a
CIE b
components
CIE L
CIE a
CIE b
A
components
CIE L
CIE C(ab)
CIE H(ab)
components
CIE L
CIE C(ab)
CIE H(ab)
A
components
hue
HCY chroma
HCY luma
alpha
components
hue
HCY chroma
HCY luma
components
hue
saturation
lightness
alpha
components
hue
saturation
lightness
components
Y'
Cb
Cr
components
Y'
Cb
Cr
alpha
components
hue
saturation
value
alpha
components
hue
saturation
value
components
cyan
magenta
yellow
key
components
cyan
magenta
yellow
bytes/pixel
32
model
RGBA
components
doubleR
doubleG
doubleB
doubleA
bytes/pixel
24
model
RGB
components
doubleR
doubleG
doubleB
bytes/pixel
32
model
RaGaBaA
components
doubleRa
doubleGa
doubleBa
doubleA
bytes/pixel
24
model
R'G'B'
components
doubleR'
doubleG'
doubleB'
bytes/pixel
32
model
R'G'B'A
components
doubleR'
doubleG'
doubleB'
doubleA
bytes/pixel
32
model
R'aG'aB'aA
components
doubleR'a
doubleG'a
doubleB'a
doubleA
bytes/pixel
3
model
R'G'B'
components
u8R'
u8G'
u8B'
bytes/pixel
4
model
R'G'B'A
components
u8R'
u8G'
u8B'
u8A
bytes/pixel
16
model
RGBA
components
floatR
floatG
floatB
floatA
bytes/pixel
12
model
RGB
components
floatR
floatG
floatB
bytes/pixel
6
model
RGB
components
halfR
halfG
halfB
bytes/pixel
8
model
RGBA
components
halfR
halfG
halfB
halfA
bytes/pixel
8
model
RaGaBaA
components
halfRa
halfGa
halfBa
halfA
bytes/pixel
6
model
R'G'B'
components
halfR'
halfG'
halfB'
bytes/pixel
8
model
R'G'B'A
components
halfR'
halfG'
halfB'
halfA
bytes/pixel
8
model
R'aG'aB'aA
components
halfR'a
halfG'a
halfB'a
halfA
bytes/pixel
6
model
RGB
components
u15R
u15G
u15B
bytes/pixel
8
model
RGBA
components
u15R
u15G
u15B
u15A
bytes/pixel
8
model
RaGaBaA
components
u15Ra
u15Ga
u15Ba
u15A
bytes/pixel
6
model
R'G'B'
components
u15R'
u15G'
u15B'
bytes/pixel
8
model
R'G'B'A
components
u15R'
u15G'
u15B'
u15A
bytes/pixel
8
model
R'aG'aB'aA
components
u15R'a
u15G'a
u15B'a
u15A
bytes/pixel
12
model
RGB
components
u32R
u32G
u32B
bytes/pixel
16
model
RGBA
components
u32R
u32G
u32B
u32A
bytes/pixel
16
model
RaGaBaA
components
u32Ra
u32Ga
u32Ba
u32A
bytes/pixel
12
model
R'G'B'
components
u32R'
u32G'
u32B'
bytes/pixel
16
model
R'G'B'A
components
u32R'
u32G'
u32B'
u32A
bytes/pixel
16
model
R'aG'aB'aA
components
u32R'a
u32G'a
u32B'a
u32A
bytes/pixel
8
model
Y
components
doubleY
bytes/pixel
16
model
YA
components
doubleY
doubleA
bytes/pixel
16
model
YaA
components
doubleYa
doubleA
bytes/pixel
8
model
Y'
components
doubleY'
bytes/pixel
16
model
Y'A
components
doubleY'
doubleA
bytes/pixel
16
model
Y'aA
components
doubleY'a
doubleA
bytes/pixel
4
model
YA
components
halfY
halfA
bytes/pixel
4
model
YaA
components
halfYa
halfA
bytes/pixel
2
model
Y
components
halfY
bytes/pixel
4
model
Y'A
components
halfY'
halfA
bytes/pixel
4
model
Y'aA
components
halfY'a
halfA
bytes/pixel
2
model
Y'
components
halfY'
bytes/pixel
4
model
YA
components
u15Y
u15A
bytes/pixel
4
model
YaA
components
u15Ya
u15A
bytes/pixel
2
model
Y
components
u15Y
bytes/pixel
4
model
Y'A
components
u15Y'
u15A
bytes/pixel
4
model
Y'aA
components
u15Y'a
u15A
bytes/pixel
2
model
Y'
components
u15Y'
bytes/pixel
8
model
YA
components
u32Y
u32A
bytes/pixel
8
model
YaA
components
u32Ya
u32A
bytes/pixel
4
model
Y
components
u32Y
bytes/pixel
8
model
Y'A
components
u32Y'
u32A
bytes/pixel
8
model
Y'aA
components
u32Y'a
u32A
bytes/pixel
4
model
Y'
components
u32Y'
bytes/pixel
24
model
Y'CbCr
components
doubleY'
doubleCb
doubleCr
bytes/pixel
32
model
Y'CbCrA
components
doubleY'
doubleCb
doubleCr
doubleA
bytes/pixel
3
model
Y'CbCr
components
u8-lumaY'
u8-chromaCb
u8-chromaCr
bytes/pixel
16
model
R'G'B'A
components
floatR'
floatG'
floatB'
floatA
bytes/pixel
8
model
R'G'B'A
components
u16R'
u16G'
u16B'
u16A
bytes/pixel
16
model
R'aG'aB'aA
components
floatR'a
floatG'a
floatB'a
floatA
bytes/pixel
8
model
R'aG'aB'aA
components
u16R'a
u16G'a
u16B'a
u16A
bytes/pixel
4
model
R'aG'aB'aA
components
u8R'a
u8G'a
u8B'a
u8A
bytes/pixel
12
model
R'G'B'
components
floatR'
floatG'
floatB'
bytes/pixel
6
model
R'G'B'
components
u16R'
u16G'
u16B'
bytes/pixel
8
model
Y'A
components
floatY'
floatA
bytes/pixel
8
model
Y'aA
components
floatY'a
floatA
bytes/pixel
4
model
Y'
components
floatY'
bytes/pixel
4
model
Y'A
components
u16Y'
u16A
bytes/pixel
4
model
Y'aA
components
u16Y'a
u16A
bytes/pixel
2
model
Y'
components
u16Y'
bytes/pixel
2
model
Y'A
components
u8Y'
u8A
bytes/pixel
2
model
Y'aA
components
u8Y'a
u8A
bytes/pixel
1
model
Y'
components
u8Y'
bytes/pixel
12
model
Y'CbCr
components
floatY'
floatCb
floatCr
bytes/pixel
16
model
Y'CbCrA
components
floatY'
floatCb
floatCr
floatA
bytes/pixel
8
model
RGBA
components
u16R
u16G
u16B
u16A
bytes/pixel
4
model
RGBA
components
u8R
u8G
u8B
u8A
bytes/pixel
16
model
RaGaBaA
components
floatRa
floatGa
floatBa
floatA
bytes/pixel
8
model
RaGaBaA
components
u16Ra
u16Ga
u16Ba
u16A
bytes/pixel
4
model
RaGaBaA
components
u8Ra
u8Ga
u8Ba
u8A
bytes/pixel
6
model
RGB
components
u16R
u16G
u16B
bytes/pixel
3
model
RGB
components
u8R
u8G
u8B
bytes/pixel
8
model
YA
components
floatY
floatA
bytes/pixel
8
model
YaA
components
floatYa
floatA
bytes/pixel
4
model
Y
components
floatY
bytes/pixel
4
model
YA
components
u16Y
u16A
bytes/pixel
4
model
YaA
components
u16Ya
u16A
bytes/pixel
2
model
Y
components
u16Y
bytes/pixel
2
model
YA
components
u8Y
u8A
bytes/pixel
2
model
YaA
components
u8Ya
u8A
bytes/pixel
1
model
Y
components
u8Y
bytes/pixel
4
model
R'G'B'
components
u8B'
u8G'
u8R'
u8PAD
bytes/pixel
24
model
CIE Lab
components
doubleCIE L
doubleCIE a
doubleCIE b
bytes/pixel
32
model
CIE Lab alpha
components
doubleCIE L
doubleCIE a
doubleCIE b
doubleA
bytes/pixel
24
model
CIE LCH(ab)
components
doubleCIE L
doubleCIE C(ab)
doubleCIE H(ab)
bytes/pixel
32
model
CIE LCH(ab) alpha
components
doubleCIE L
doubleCIE C(ab)
doubleCIE H(ab)
doubleA
bytes/pixel
12
model
CIE Lab
components
floatCIE L
floatCIE a
floatCIE b
bytes/pixel
16
model
CIE Lab alpha
components
floatCIE L
floatCIE a
floatCIE b
floatA
bytes/pixel
8
model
CIE Lab alpha
components
floatCIE L
floatA
bytes/pixel
3
model
CIE Lab
components
CIE u8 LCIE L
CIE u8 abCIE a
CIE u8 abCIE b
bytes/pixel
6
model
CIE Lab
components
CIE u16 LCIE L
CIE u16 abCIE a
CIE u16 abCIE b
bytes/pixel
12
model
CIE LCH(ab)
components
floatCIE L
floatCIE C(ab)
floatCIE H(ab)
bytes/pixel
16
model
CIE LCH(ab) alpha
components
floatCIE L
floatCIE C(ab)
floatCIE H(ab)
floatA
bytes/pixel
32
model
HCYA
components
doublehue
doubleHCY chroma
doubleHCY luma
doublealpha
bytes/pixel
24
model
HCY
components
doublehue
doubleHCY chroma
doubleHCY luma
bytes/pixel
16
model
HCYA
components
floathue
floatHCY chroma
floatHCY luma
floatalpha
bytes/pixel
12
model
HCY
components
floathue
floatHCY chroma
floatHCY luma
bytes/pixel
4
model
R'aG'aB'aA
components
u8B'a
u8G'a
u8R'a
u8A
bytes/pixel
32
model
HSLA
components
doublehue
doublesaturation
doublelightness
doublealpha
bytes/pixel
24
model
HSL
components
doublehue
doublesaturation
doublelightness
bytes/pixel
16
model
HSLA
components
floathue
floatsaturation
floatlightness
floatalpha
bytes/pixel
12
model
HSL
components
floathue
floatsaturation
floatlightness
bytes/pixel
4
model
R'aG'aB'aA
components
u8B'a
u8G'a
u8R'a
u8A
bytes/pixel
1
model
YA
components
u8A
bytes/pixel
24
model
Y'CbCr709
components
doubleY'
doubleCb
doubleCr
bytes/pixel
32
model
Y'CbCrA709
components
doubleY'
doubleCb
doubleCr
doublealpha
bytes/pixel
16
model
Y'CbCrA709
components
floatY'
floatCb
floatCr
floatalpha
bytes/pixel
12
model
Y'CbCr709
components
floatY'
floatCb
floatCr
bytes/pixel
32
model
HSVA
components
doublehue
doublesaturation
doublevalue
doublealpha
bytes/pixel
24
model
HSV
components
doublehue
doublesaturation
doublevalue
bytes/pixel
16
model
HSVA
components
floathue
floatsaturation
floatvalue
floatalpha
bytes/pixel
12
model
HSV
components
floathue
floatsaturation
floatvalue
bytes/pixel
32
model
CMYK
components
doublecyan
doublemagenta
doubleyellow
doublekey
bytes/pixel
24
model
CMY
components
doublecyan
doublemagenta
doubleyellow
bytes/pixel
16
model
CMYK
components
floatcyan
floatmagenta
floatyellow
floatkey
bytes/pixel
12
model
CMY
components
floatcyan
floatmagenta
floatyellow
bytes/pixel
4
model
CMYK
components
u8cyan
u8magenta
u8yellow
u8key

Shortcut Coverage

The diagram shown below visualizes the coverage of current shortcut conversions. Dots indicate a direct conversion is provided for, the height of the bar indicates the number of conversions steps needed in a chain of conversions.

Environment

Through the environment variable BABL_TOLERANCE you can control a speed/performance trade off that by default is set very low (0.000001) values in the range 0.01-0.1 can provide reasonable preview performance by allowing lower numerical accuracy

.

BABL_PATH contains the path of the directory, containing the .so extensions to babl.

Extending

For samples of how the current internal API 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).

Directory Overview

babl-dist-root
 │
 ├──babl       the babl core
 │   └──base   reference implementations for RGB and Grayscale Color Models,
 │             8bit 16bit, and 32bit and 64bit floating point.
 ├──extensions CIE-Lab color model as well as a naive-CMYK color model.
 │             also contains a random cribbage of old conversion optimized
 │             code from gggl. Finding more exsisting conversions in third
 │             part libraries (hermes, lcms?, liboil?) could improve the
 │             speed of babl.
 ├──tests      tests used to keep babl sane during development.
 └──docs       Documentation/webpage for babl (the document you are reading
               originated there.

TODO

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 3 of the License, or (at your option) any later version.

Authors

Øyvind Kolås pippin at gimp.org
Original author.
Sven Neumann sven at gimp.org
Build sanity and optimizations.
Michael Natterer mitch at gimp.org
Build sanity.
Kevin Cozens kcozens at cvs.gnome.org
Build sanity.
Tim Mooney
Portability fixes.
Michael Schumacher schumaml at cvs.gnome.org
win32 support for dynamic extensions.
Portability fixes.
Jan Heller jheller at svn.gnome.org
Optimizations, refactoring and documentation.
Mukund Sivaraman muks at mukund.org
Sparse fixes and sanity.
dmacks at netspace.org
Build sanity
Sam Hocevar
Build sanity.
Zhang Junbo
Frequency domain color model.
Martin Nordholts
Optimizations and API overhaul.
Gary V. Vaughan
Multiplatform build support.
Stanislav Brabec
Portability patch.
Hubert Figuiere
C++ friendliness patch.
Danny Robson
Code cleanups.
Fryderyk Dziarmagowski freetz at gmx.net
Code cleanups.
Daniel Paredes García danipga at gmail.com
Initial work to make babl threadsafe
Rupert Weber gimp at leguanease.org
Documentation and other improvements
Jehan jehan at girinstud.io
win32 portabilitiy
Sven Claussner
Update DOAP file
Alexander Larsson
Math optimizations
Nils Philippsen
code cleanups
Simon Budig
cleanups
Micheal Muré
portability fixes
Edward E
win32 platform adaptations
Maxime Nicco
HSV color model extension
Teo Mazars
Color spaces/models in extensions
Daniel Sabo
Dead code elimination, general cleanups,
Michael Henning
Conversion fixes
Elle Stone
Verification and improvements to accuracy of color space conversions.
Thomas Manni
CIE related fixups
Roman Lebedev
Stability/crasher fixes
Jon Nordby
Portability, Stability and more
Massimo Valentini
stability fixes
Ell
fast paths
/babl-0.1.33