Generate FOD-based DEC maps, with optional panchromatic sharpening and/or luminance/perception correction


fod2dec [ options ]  input output
  • input: The input FOD image (spherical harmonic coefficients).

  • output: The output DEC image (weighted RGB triplets).


By default, the FOD-based DEC is weighted by the integral of the FOD. To weight by another scalar map, use the -contrast option. This option can also be used for panchromatic sharpening, e.g., by supplying a T1 (or other sensible) anatomical volume with a higher spatial resolution.


  • -mask image Only perform DEC computation within the specified mask image.

  • -contrast image Weight the computed DEC map by the provided image contrast. If the contrast has a different image grid, the DEC map is first resliced and renormalised. To achieve panchromatic sharpening, provide an image with a higher spatial resolution than the input FOD image; e.g., a T1 anatomical volume. Only the DEC is subject to the mask, so as to allow for partial colouring of the contrast image.
    Default when this option is not provided: integral of input FOD, subject to the same mask/threshold as used for DEC computation.

  • -lum Correct for luminance/perception, using default values Cr,Cg,Cb = 0.3,0.5,0.2 and gamma = 2.2 (not correcting is the theoretical equivalent of Cr,Cg,Cb = 1,1,1 and gamma = 2).

  • -lum_coefs values The coefficients Cr,Cg,Cb to correct for luminance/perception.
    Note: this implicitly switches on luminance/perception correction, using a default gamma = 2.2 unless specified otherwise.

  • -lum_gamma value The gamma value to correct for luminance/perception.
    Note: this implicitly switches on luminance/perception correction, using a default Cr,Cg,Cb = 0.3,0.5,0.2 unless specified otherwise.

  • -threshold value FOD amplitudes below the threshold value are considered zero.

  • -no_weight Do not weight the DEC map; just output the unweighted colours. Reslicing and renormalising of colours will still happen when providing the -contrast option as a template.

Standard options

  • -info display information messages.

  • -quiet do not display information messages or progress status; alternatively, this can be achieved by setting the MRTRIX_QUIET environment variable to a non-empty string.

  • -debug display debugging messages.

  • -force force overwrite of output files (caution: using the same file as input and output might cause unexpected behaviour).

  • -nthreads number use this number of threads in multi-threaded applications (set to 0 to disable multi-threading).

  • -config key value (multiple uses permitted) temporarily set the value of an MRtrix config file entry.

  • -help display this information page and exit.

  • -version display version information and exit.


Dhollander T, Smith RE, Tournier JD, Jeurissen B, Connelly A. Time to move on: an FOD-based DEC map to replace DTI’s trademark DEC FA. Proc Intl Soc Mag Reson Med, 2015, 23, 1027

Dhollander T, Raffelt D, Smith RE, Connelly A. Panchromatic sharpening of FOD-based DEC maps by structural T1 information. Proc Intl Soc Mag Reson Med, 2015, 23, 566

Tournier, J.-D.; Smith, R. E.; Raffelt, D.; Tabbara, R.; Dhollander, T.; Pietsch, M.; Christiaens, D.; Jeurissen, B.; Yeh, C.-H. & Connelly, A. MRtrix3: A fast, flexible and open software framework for medical image processing and visualisation. NeuroImage, 2019, 202, 116137

Author: Thijs Dhollander (

Copyright: Copyright (C) 2014 The Florey Institute of Neuroscience and Mental Health, Melbourne, Australia. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.