lvdetilt(3)            C LIBRARY FUNCTIONS            lvdetilt(3)



LIBRARY ROUTINE
     lvdetilt - Remove an illumination gradient from an image  by
     subtracting a best-fit plane.

LIBRARY CALL
          #include "vinclude.h"
          int
          lvdetilt(img1,img2,mflg,pflg)
          struct xvimage *img1,*img2;
          int  mflg, pflg;

INPUT
     img1           (struct xvimage) - input/output image  struc-
                    ture

     img2           (struct xvimage) - gating mask image

     mflg           (int) - a flag set (equal 1) if gating  image
                    mask available

                    The input images must be  of  the  same  data
                    type and size.

OUTPUT
     img1           (struct xvimage) - holds the  result  of  the
                    detilt  operation.   The  output data type is
                    the same as the input data type.

MODIFICATIONS
     John Rasure, Marcelo Teran, Ron E. Neher

     Mon Jun 11 15:59:36 MDT 1990 Donna  Koechner  -  updated  to
     ghostwriter

     Wed Mar 20 12:36:43 MET 1991  Jean  Pierre  Guerin  -  Fixed
     incorrect tilt center point calculation

     26-Sep-91 Scott Wilson - Fixed undocumented  change  in  the
     lib source (not recorded in vdetilt.prog) that had incorrect
     checks for the successful completion of the tilt computation
     routines.  For  the  float  case,  success  was  incorrectly
     detected as failure, resulting in bogus error  messages  and
     premature termination of the routine.

DESCRIPTION
     _l_v_d_e_t_i_l_t computes the best-fit plane for an image, and  then
     subtracts  that  plane from the image to produce the output.
     This is very handy for correcting illumination gradients  in
     a  poorly  digitized  image.  The pflg also removes the mean
     from the image, giving it zero-mean statistics.





Sun Release 4.1       Last change: 09/26/9                      1






lvdetilt(3)            C LIBRARY FUNCTIONS            lvdetilt(3)



     The mask image must be of the same data type  as  the  input
     images,  and is used to gate the operation.  A non-zero mask
     pixel enables the  output  pixel  to  contain  the  adjusted
     value.  A  zero  mask  pixel just transfers the value of the
     corresponding pixel in the input image to the output pixel.

     img1 is the input image and img2  is  the  operation  gating
     image.   mflg should be set to one if the gating image is to
     be used.  img1 is used for both the input xvimage  structure
     and  the  output  result xvimage structure.  This is done to
     save space, but you must be careful not to overwrite  impor-
     tant data.

     The mask image must be the same size as  the  input  images.
     The  output  image  data type is the same as the input image
     data type.  _l_v_d_e_t_i_l_t returns a value of one upon success and
     a zero on failure.

SEE ALSO
     vdetilt(1), intro(3), vipl(3),  verror(3),  vutils(3)  vget-
     tilt(1), lvgettilt(3), vtilt(1), lvtilt(3)

RESTRICTIONS
     _l_v_d_e_t_i_l_t will not work on BIT,  transform  or  COMPLEX  data
     storage types.

AUTHOR
     Scott Wilson


COPYRIGHT
     Copyright  1991,  University  of  New  Mexico.   All  rights
     reserved.






















Sun Release 4.1       Last change: 09/26/9                      2