NAME

       fiarith - evaluating arithmetic expressions on images as operands

SYNOPSIS

       fiarith [options] "<expression>" [-o|--output <output.fits>]

DESCRIPTION

       The  purpose  of  this  program  is  to  evaluate  <expression>  which  is intented to contain arithmetic
       operations and functions on FITS images (of the same size). See the section "Examples" below for examples
       on the syntax of <expression>

OPTIONS

   General options:
       -h, --help
              Gives general summary about the command line options.

       --long-help, --help-long
              Gives a detailed list of command line options.

       --wiki-help, --help-wiki, --mediawiki-help, --help-mediawiki
              Gives a detailed list of command line options in Mediawiki format.

       --version, --version-short, --short-version
              Gives some version information about the program.

       -o, --output <fits>
              The name of the output file (omitting or specifing '-' yields the output to be written to stdout).

       -s, --size <sx>,<sy>
              Horizontal  and  vertical  size  of  the  output  image  (meaningless if <expression> contains any
              existing FITS image).

       -M, --input-mask <fits>
              Input mask file to co-add to output image.

       --output-mask <fits>
              Name of output mask file to create.

       -D, --data <spec>
              Output pixel data format specification.

       -b, --bitpix <bitpix>
              Standard FITS output bitpix value.

       -a, --apply-mask
              Resets pixel values to zero if masked.

       -e, --header <fits>
              Inherit output header from the specified FITS file.

   Available arithmetic operators:
       +      Addition.

       -      Subtraction.

       *      Multiplication.

       /      Division. Dividing by zero yields zero automatically.

   Available arithmetic functions:
       sin(.), cos(.), tan(.)
              Trigonometric functions.

       asin(.), acos(.), atan(.), atan2(.,.), arg(.,.)
              Inverse trigonometric functions.

       abs(.), sq(.), sqrt(.), exp(.), log(.)
              Absolute value, square, Square root, exponential and natural logarithm functions.

   Available image functions:
       min(....)
              The per pixel minimal value of pixel intensities of the images listed (separated by comma) in  the
              argument of the function.

       max(....)
              The  per pixel maximal value of pixel intensities of the images listed (separated by comma) in the
              argument of the function.

       mean(...)
              The per pixel mean value of pixel intensities of the images listed (separated  by  comma)  in  the
              argument of the function.

       norm(.)
              The mean of the pixel values on the image.

       sign(.)
              The per pixel sign function.

       theta(.)
              The per pixel Heaviside step function.

       laplace(.)
              The Laplace transform of the image.

       scatter(.)
              Noise level estimation for the image.

       corr(.,.)
              Correlation between two images.

       smooth(<image>,<sigma>,<size>)
              The  smoothed  variant  of  the  first  argument  (threated  as an image), which is yielded by the
              convolution with a Gaussian profile with a standard deviation of <sigma>, evaluated  on  a  kernel
              stamp with the size of <size>.

EXAMPLES

       fiarith "'img1.fits'-'orig.fits'" -o diff.fits
              Calculates  the  per  pixel  difference  between images "img1.fits" and "orig.fits" and stores the
              result in "diff.fits".

       fiarith -s 512,512 "137.42" -o constant.fits
              Creates a new image with the size of 512 by 512 pixels with the constant value of 137.42.

       fiarith "'-'*26" -o -
              Multiplies the pixel intensities of the image read from the standard input by 26  and  writes  the
              result  to  the  standard output. The "-o -" can either be omitted, since by default the output is
              written to stdout.

       fiarith -s 512,512 "['input.fits'](a/(1-0.3*(X^2-Y^2)))" -o flattened.fits
              This invocation evaluates  the  "a/(1-0.3*(X^2+Y^2))"  expression  on  each  pixel  of  the  image
              "input.fits",  where  "a" referes to the pixel value itself and X and Y are the normalized spatial
              coordinates. The normalization is always done as X=(2*x-SX)/(SX) and Y=(2*y-SY)/SX, i.e. the X and
              Y  coordinates  are zero at the center of the images, X has a unity absolute value at the left and
              right edges and Y is scaled properly to X.

       fiarith "('R.fits'-'B.fits'-0.5*'D.fits')*(norm('F.fits')/'F.fits')" -o C.fits
              This operation performs a simple bias, dark and flat calibration on the input raw image  "R.fits",
              expecting "B.fits", "D.fits" and "F.fits" to be the master bias, dark and flat calibration frames,
              respectively; and assuming an exposure time for the raw image which is the half  of  the  exposure
              time  of  the  master dark frame. Due to the "norm(...)" function, the mean intensity level of the
              image is kept to be the same as it is in the raw image.

REPORTING BUGS

       Report bugs to <apal@szofi.net>, see also http://fitsh.net/.

COPYRIGHT

       Copyright © 1996, 2002, 2004-2008, 2010-2015; Pal, Andras <apal@szofi.net>