FIMGZIP (Jul92)               ftools.fimage              FIMGZIP (Jul92)



NAME
    fimgzip -- Compress an image into a variable-length column in a FITS
               binary table.
    
    
USAGE
    fimgzip infile outfile algorithm
    
    
DESCRIPTION
    This  task will compress the n-dimensional (n<=3) images and storing
    the resulting bytes in a variable-length column  in  a  FITS  binary
    table.  The  program  first  divides  the n-dimensional image into a
    rectangular  grid  of  subimages  or  `tiles'.  Each  tile  is  then 
    compressed  as  a  continuous  block  of  data,  and  the  resulting 
    compressed byte stream is stored in  a  row  of  a  variable  length
    column  in  a FITS binary table. By dividing the image into tiles it
    is generally possible to extract and uncompress subsections  of  the
    image  without  having  to  uncompress  the whole image. The default
    tiling pattern treats each row of a 2-dimensional image  (or  higher
    dimensional  cube)  as  a  tile, such that each tile contains NAXIS1
    pixels.  However,  users  can  change  this  default  convention  by 
    supplying their own xtilesize, ytilesize and ztilesize parameters.
    
    For   the   compressed  method,  users  can  choose  it  from  three 
    algorithms, RICE, GZIP, and PLIO. The  details  of  these algorithms  
    can be found in the URLS:     

    http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/compress/compress_image.html
    
    
    
PARAMETERS
    
    infile [filename]
        The input FITS file and the image extension.
    
    outfile [filename]
        The output FITS file name. If  the  file  does  not  exist,  the
        program  will  create  one  for  you.  Otherwise, the compressed
        image table will be appended at the end of the file.
    
    algorithm = "RICE" [string]
        The choosed algorithm. It can be one  of  the  RICE,  GZIP,  and
        PILO. The default algorithm is RICE.
    
    (xtilesize = INDEF)  [integer]
        X dimension of the tiles. The default value is NAXIS1.
    
    (ytilesize = INDEF)  [integer]
        Y dimension of the tiles. The default value is 1.
    
    (ztilesize = INDEF)  [integer]
        Z dimension of the tiles. The default value is 1.
    
    (blocksize = 32)  [integer]
        Compression parameter. Only used for RICE algorithm.
    
    (nbit = 4)  [integer]
        Compression  parameter for float images. Only takes values from 0
        to 8.
    
    (clobber = no) [boolean]
        If true, an existing file with the same name  as  the  requested
        output file will be overwritten.
    
    
EXAMPLES 
    Compress  an image in test.fits[3] using RICE algorithm, and put the
    output to the file of test_compress.fits
    
            ft>fimgzip test.fits+3 test_compress.fits RICE
    
    
BUGS
    
    
SEE ALSO
    fimgunzip