babl (original) (raw)

babl is pixel encoding and color space conversion engine in C.

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

The pixel data storage in GIMP usesGEGL's GeglBuffer which internally stores tiles and provides an API for retrieving and storing pixel data with implicit conversions using babl formats.

Download

The latest versioned development version of babl can be found inhttps://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 https://gitlab.gnome.org/GNOME/babl.git/

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.

2024-02-09 babl-0.1.108

"double" and "half" support in cli-tool, build fixes.

2023-05-05 babl-0.1.106

Disable LUTs on big-endian, fix to 1bpp->4bpp LUTs, faster startup by caching balanced RGB to XYZ matrices.

2023-04-21 babl-0.1.104

LUT code-paths re-enabled, some array overflow proofing.

2023-02-25 babl-0.1.102

Brown paper bag release - LUT code-paths now disabled by default.

2023-02-20 babl-0.1.100

Stop double processing with LUT+normal fishes. Support for non-ASCII characters in file paths on windows. Improved wrap build support.

2022-11-13 babl-0.1.98

More robust bounds protection in ICC handling, avoid garbage collecting lookup tables in-line with processing.

2022-08-23 babl-0.1.96

Minor changes from 0.1.94, fixing build.

2022-08-21 babl-0.1.94

Fix of crash on non-aligned data for SIMD, add commandline tool, improve vala compatibility of introspection info.

2022-03-22 babl-0.1.92

Fixes for avoiding load of wrong SIMD extensions.

2022-02-21 babl-0.1.90

Automatic LUT creation for conversions from <24bpp of colorant componants, SIMD builds for x86_64 micro-architecture levels and ARM neon, pre-defined CIE Lab u8 and CIE Lab u16 formats. Fix bug of an unlocked non-locked mutex, which started failing on some platforms.

2021-07-01 babl-0.1.88

Consistency fixes to format names, in particular for palettized formats.

2021-02-26 babl-0.1.86

input-class (scanner/RGB) ICC profiles are valid for creating RGB spaces. improved thread safety for babl_space_from_icc build: allow using babl a subproject in other meson projects.

2020-12-17 babl-0.1.84

Fixed bug in caching of CMYK ICC profiles.

2020-10-04 babl-0.1.82

Handle the parametric ICCv4 types that are not strictly the same type as core sRGB curve.

2020-08-02 babl-0.1.80

meson build cleanups, depend on meson 0.54

2020-06-07 babl-0.1.78

Bugfix release - mutex and atomicity related issues.

2020-05-27 babl-0.1.76

Wrap hue in HSV, HSL, HCY. Fix black pullout in non ICC CMYK conversion. Added AV2 gamme u8->linear float conversions. VAPI file generation for vala integration. Adjusted strategy for conversion selection, trades back warm-up time for missing some fast multi-step conversions.

2019-08-22 babl-0.1.74

Build fixes, improved host cpu detection, OSX fixes, clang warning squelches. 2019-08-22 babl-0.1.72

Added handling for grayscale ICC profiles and gobject introspection support. Optimizations for many format conversions for u8, u16 and half formats. And fixed a crash for NANs in float to u8 conversions.

2019-08-02 babl-0.1.70

Build fixes making the meson build work with more architectures.

2019-07-25 babl-0.1.68

Added Yu'v' (CIE 1976 UCS) color model. Fixed a severe non-initialised memory issue - that kept us from using fast paths for many babl spaces loaded from profile. More fully symmetric conversions between associated and separate alpha. Added more converters, both SSE2 and non-SSE2 for matrix-conversion between different RGB spaces. Improvements to website/documentation; babl is now using the terms associated alpha and separate alpha, all of: nonpremultiplied-, premultiplied- and nonassociated- alpha are now considered deprecated API. HCY luminance is now relative to the RGB space used - no change for sRGB related pixel formats. AVX2 acceleration for some linear to float conversions.

2019-06-12 babl-0.1.66

Added API call, babl_space_get_rgb_luminance, Make most SIMD code-paths optional again on i686.

2019-05-25 babl-0.1.64

Support for Hygon Dhyana, and Y~aA formats for symmetric completeness. Code consistency, gitlab CI, autotools and meson build improvements.

2019-02-01 babl-0.1.62

Continuous integration with gitlab. Initial CMYK spaces with lcms2 based ICC support, much room for optimization. Improved custom space support for palette formats. scRGB space, works like sRGB but always with linear TRCs. Model introspection API permitting low overhead checks whether a format/model is RGB, CMYK type of alpha and similar.

For more detailed changes see git log.

Usage

Most users of babl do not know they are using babl and it is GIMP itself which uses babl, this is documentation for such uses - and others that might want to use babl for pixel format or color space conversion in other software.

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). Color Spaces can be created from chromaticity coordinates or ICC profiles. The reference color space - to maintain fast and bit-accurate conversions on with sRGB is similar to scRGB using 64bit floating point.

To speed up operations, fast path conversions are used. 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.

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 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);

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. ├──tools various commandline tools used for verifying accuracy of extensions. ├──tests tests used to keep babl sane during development. └──docs Documentation/webpage for babl (the document you are reading originated there.

TODO

These are among desired or expected changes to babl, that are missing.

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

CIE xyY color space

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

Guiu Rocafort

sanity crash fix

Tobias Stoeckmann

bug fixes for leaks and crashers

Debarshi Ray

SSE2 version of CIE code paths

Félix Piédallu

Meson build; original port, and improvements.

Yaakov Selkowitz

Cygwin patch

Étienne Bersac

build/packaging

Nuno Ferreira

coding style fixes

John Marshall

meson build improvements

babl