NAME

       astscript-color-faint-gray - RGB image from FITS images showing bright and faint features

SYNOPSIS

       astscript-color-faint-gray [OPTION] R.fits G.fits B.fits K.fits

DESCRIPTION

       This script is part of GNU Astronomy Utilities 0.24.

       This  script generates a color image from three different images (RGB). In order to show the entire range
       of pixel values, an asinh transformation is used. For more on the definiton of this algorithm see  Lupton
       et al. 2004:

              https://doi.org/10.1086/382245

       For  more  information, please run any of the following commands. In particular the first contains a very
       comprehensive explanation  of  this  script's  invocation:  expected  input(s),  output(s),  and  a  full
       description of all the options.

       Inputs/Outputs and options:
              $ info astscript-color-faint-gray

       Full Gnuastro manual/book:
              $ info gnuastro

       If  you  couldn't find your answer in the manual, you can get direct help from experienced Gnuastro users
       and developers. For more information, please run:

              $ info help-gnuastro

   astscript-color-faint-gray options:
              Input:

       -h, --hdu=STR
              HDU/extension for the input channels.

       -r, --reghdu=STR
              HDU/extension for the regions image.

       -g, --globalhdu=STR/INT Use this HDU for all inputs, ignore '--hdu'.

       -w, --weight=FLT
              Relative weight for each input channel.

       -m, --minimum=FLT
              Minimum value for each input channel.

       -z, --zeropoint=FLT
              Zero point magnitude of each input channel.

              Asinh scaling parameters

       -Q, --qbright=FLT
              Parameter for bringing out brighter features.

       -s, --stretch=FLT
              Linear stretching parameter for faint features.

              Contrast, bias, and marks

       -b, --bias
              Constant (bias) to add to all the pixels (linear).

       -c, --contrast
              Change the contrast of the final image (linear).

       -G, --gamma
              Gamma (nonlinear, overrides bias/contrast).

       --markoptions=STR
              Options to add marks (passed to ConvertType).

              Color and gray parameters

       --coloronly
              No grayscale regions, background in color (black).

       --regions=STR
              Regions labeled image (color=2, black=1, gray=0).

       --grayval=FLT
              Gray threshold (highest value to use grayscale).

       --colorval=FLT
              Color threshold (lowest value to have color).

       --graykernelfwhm=FLT
              Kernel FWHM for convolving the background image.

       --colorkernelfwhm=FLT Kernel FWHM for color separation ref. image.

              Output:

       -k, --keeptmp
              Keep temporary/auxiliar files.

       -o, --output
              Output color image name.

       --checkparams
              Print distribution of values used to find params.

              Operating mode:

       -h, --help
              Print this help list.

       -q, --quiet
              Don't print the list.

       -V, --version
              Print program version.

       --cite BibTeX citation for this program.

       Mandatory or optional arguments to long options are also mandatory  or  optional  for  any  corresponding
       short options.

       GNU Astronomy Utilities home page: http://www.gnu.org/software/gnuastro/

REPORTING BUGS

       Report bugs to bug-gnuastro@gnu.org.

COPYRIGHT

       Copyright © 2021-2025, Free Software Foundation, Inc.  License GPLv3+: GNU General public license version
       3 or later.
       This  is  free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent
       permitted by law.

       Written/developed by Raul Infante-Sainz and Mohammad Akhlaghi.

SEE ALSO

       The full documentation for astscript-color-faint-gray is maintained as a Texinfo manual.  If the info and
       astscript-color-faint-gray programs are properly installed at your site, the command

              info astscript-color-faint-gray

       should give you access to the complete manual.

GNU Astronomy Utilities 0.24                      November 2025                    ASTSCRIPT-COLOR-FAINT-GRAY(1)