PFILT(1)                                                              PFILT(1)



NNAAMMEE
       pfilt - filter a RADIANCE picture

SSYYNNOOPPSSIISS
       ppffiilltt [ ooppttiioonnss ] [ ffiillee ]

DDEESSCCRRIIPPTTIIOONN
       _P_f_i_l_t  performs  anti-aliasing  and scaling on a RADIANCE picture.  The
       program makes two passes on the picture file in order to set the  expo-
       sure  to  the correct average value.  If no _f_i_l_e is given, the standard
       input is read.

       --xx _r_e_s    Set the output x resolution to _r_e_s_.  This must be  less  than
                 or  equal to the x dimension of the target device.  If _r_e_s is
                 given as a slash followed by a real number, the input resolu-
                 tion  is divided by this number to get the output resolution.
                 By default, the output resolution is the same as the input.

       --yy _r_e_s    Set the output y resolution to _r_e_s_, similar to the specifica-
                 tion of the x resolution above.

       --pp _r_a_t    Set  the  pixel  aspect  ratio to _r_a_t_.  Either the x or the y
                 resolution will be reduced so that the pixels have this ratio
                 for  the specified picture.  If _r_a_t is zero, then the x and y
                 resolutions will adhere to the given  maxima.   Zero  is  the
                 default.

       --cc        Pixel aspect ratio is being corrected, so do not write PIXAS-
                 PECT variable to output file.

       --ee _e_x_p    Adjust the exposure.  If _e_x_p is preceded by a '+' or '-', the
                 exposure  is  interpreted  in f-stops (ie. the power of two).
                 Otherwise, _e_x_p is interpreted as a straight multiplier.   The
                 individual  primaries  can be changed using _-_e_r_, _-_e_g and _-_e_b_.
                 Multiple exposure options have a cumulative effect.

       --tt lamp   Color-balance the image as if it were illuminated by fixtures
                 of  the  given  type.  The specification must match a pattern
                 listed in the lamp lookup table (see the -f option below).

       --ff lampdat
                 Use the specified lamp lookup table rather than  the  default
                 (lamp.tab).

       --11        Use  only  one pass on the file.  This allows the exposure to
                 be controlled absolutely, without any averaging.  Note that a
                 single  pass  is much quicker and should be used whenever the
                 desired exposure is known and star patterns are not required.

       --22        Use two passes on the input.  This is the default.

       --bb        Use  box  filtering  (default).   Box  filtering averages the
                 input pixels corresponding to each separate output pixel.

       --rr _r_a_d    Use Gaussian filtering with a radius of _r_a_d relative  to  the
                 output  pixel size.  This option with a radius around 0.6 and
                 a reduction in image width and height of 2 or 3 produces  the
                 highest  quality pictures.  A radius greater than 0.7 results
                 in a defocused picture.

       --mm _f_r_a_c   Limit the influence of any given input pixel to _f_r_a_c  of  any
                 given  output pixel.  This option may be used to mitigate the
                 problems associated with inadequate image  sampling,  at  the
                 expense  of  a  slightly  blurred  image.  The fraction given
                 should not exceed the  output  picture  dimensions  over  the
                 input  picture dimensions (x_o*y_o/x_i/y_i), or blurring will
                 occur over the entire image.   This  option  implies  the  _-_r
                 option  for Gaussian filtering, which defaults to a radius of
                 0.6.

       --hh _l_v_l    Set intensity considered ``hot'' to _l_v_l_.  This is  the  level
                 above  which  areas  of  the image will begin to exhibit star
                 diffraction  patterns  (see  below).   The  default  is   100
                 watts/sr/m2.

       --nn _N      Set  the  number of points on star patterns to _N_.  A value of
                 zero turns star patterns off.  The default is 0.  (Note  that
                 two passes are required for star patterns.)

       --ss _v_a_l    Set the spread for star patterns to _v_a_l_.  This is the value a
                 star pattern will have at the edge of the image.  The default
                 is .0001.

       --aa        Average hot spots as well.  By default, the areas of the pic-
                 ture above the hot level are not used in  setting  the  expo-
                 sure.

EENNVVIIRROONNMMEENNTT
       RAYPATH        directories to search for lamp lookup table

FFIILLEESS
       /tmp/rt??????

AAUUTTHHOORR
       Greg Ward

SSEEEE AALLSSOO
       getinfo(1),  ies2rad(1),  pcompos(1),  pflip(1), pinterp(1), pvalue(1),
       protate(1), rad(1), rpict(1), ximage(1)



RADIANCE                            11/8/96                           PFILT(1)
