Convert a gradation function in a 1D/2D LUT.

Supported output formats : csp, cube, 3dl, spi1d, spi3d, cc (Ace Color Cube), lut, json… (to be continued)

Curve to LUT let you process LUTs that correspond to the gradation of a standard color space (for which we know the mathematical functions) :

  • sRGB to lin (and its inverse),
  • AlexaLogCV3 to lin (and its inverse),
  • But also Gamma 2.2 to lin (and its inverse),
  • …

Process from the mathematical functions (and not from another LUT) allows to compute a more precise LUT.

Available gradations :

  • ACESlog_16i / ACESlog_32f, ACESproxy_10 / ACESproxy_12,
  • AlexaLogCV3,
  • DCI / DCI_D60,
  • Rec2020_10bits / Rec2020_12bits,
  • Rec709,
  • sRGB,
  • SGamut3CineSLog3, SGamutSLog, SGamutSLog2,
  • SGamutSLog3,
  • WideGamut,
  • gamma custom,
  • to be continued …

Required parameters

  • outlutfile : path to the output LUT or to the output directory.
    If it’s a directory : LUT name will be deduced from the applied transformation.

Gradation options

  • –colorspace : standard color space. Possible values : ACESlog_16i / ACESlog_32f, ACESproxy_10 / ACESproxy_12, AlexaLogCV3, DCI / DCI_D60, Rec2020_10bits / Rec2020_12bits, Rec709, sRGB, SGamut3CineSLog3, SGamutSLog, SGamutSLog2, SGamutSLog3, WideGamut

OR

  • –gamma : gamma value. Ex: 1.8, 2.2, 2.4…

LUT export options

You need to define at least a type (1D, 2D, 3D) and an output format (csp, cube, 3dl…) OR a preset.

  • –out_type : 1D, 2D, 3D. Output LUT type. Beware: every format doesn’t support each type. See format help.

  • –out_format : 3dl,csp,cube,lut,spi,clcc,json. Output LUT format. Beware: 3dl, clcc, json are 3D only and lut is 1D/2D only.

OR

  • –preset : lustre_3d, scratch_1d, scratch_3d, rv_3d, resolve_3d, csp_1d, clipster_1d, lustre_1d, clipster_3d, smoke_flame_3d . Use a LUT export preset to set output LUT arguments

Find out more about presets.

Warning : Curve to LUT doesn’t prevent you from writing those LUTs in 3D formats. However it’s strongly advised to use 1D/2D LUTs. A 3D LUT may not be precise enough to bake a gradation.

Optional parameters

Gradation parameters

  • –direction : encode (lin to color space or gamma) or decode (color space or gamma to lin). Default : encode.

  • –process-input-range : compute automatically input range. Useful when a transformation goes far beyond classical [0.0, 1.0] range to process a LUT that doesn’t clip. Ex : Lin to Log.

LUT export parameters

  • –input-range : Input range. Ex: 0.0 1.0 or 0 4095.

  • –output-range : Output range. Ex: 0.0 1.0 or 0 4095

  • –out-bit-depth : Output lut bit precision (1D only). Ex : 10, 16, 32.

  • –out-cube-size : Output cube size (3D only). Ex : 17, 33.

  • –overwrite-preset : If a preset + other options are specified, it will overwrite preset values with the option values. Ex: –preset lustre –output-range [0, 255], will use range defined by –output-range

  • –inverse : Invert input LUT (1D only)

  • –smooth-size : smooth sub-sampling size (1D only). Ex : 10

Debug parameters

  • –version : show program’s version number and exit

  • –full-versions : show version number of the program and its dependencies. And then exit

  • –silent : hide log

  • –trace : in case of error, print stack trace

Usage example

Lustre supports a specific 1D/2D LUT format. A preset is available to export this format.

curve_to_lut --colorspace sRGB --preset lustre_3d /path/
This command will write /path/Lin_to_sRGB.lut (we encode by default).

To get inverse transform:

curve_to_lut --colorspace sRGB --preset lustre_3d --direction decode /path/
This command will write /path/sRGB_to_Lin.lut.

All options can always be displayed with : curve_to_lut -h

For more tips on command line usage and export options, see LUT to LUT example.