NAME
pfilt - filter a RADIANCE picture
SYNOPSIS
pfilt [ options ] [ file ]
DESCRIPTION
Pfilt performs anti-aliasing and scaling on a RADIANCE picture. The
program makes two passes on the picture file in order to set the
exposure to the correct average value. If no file is given, the
standard input is read.
-x res Set the output x resolution to res. This must be less than
or equal to the x dimension of the target device. If res is
given as a slash followed by a real number, the input
resolution is divided by this number to get the output
resolution. By default, the output resolution is the same as
the input.
-y res Set the output y resolution to res, similar to the
specification of the x resolution above.
-p rat Set the pixel aspect ratio to rat. Either the x or the y
resolution will be reduced so that the pixels have this ratio
for the specified picture. If rat is zero, then the x and y
resolutions will adhere to the given maxima. Zero is the
default.
-c Pixel aspect ratio is being corrected, so do not write
PIXASPECT variable to output file.
-e exp Adjust the exposure. If exp is preceded by a ’+’ or ’-’, the
exposure is interpreted in f-stops (ie. the power of two).
Otherwise, exp is interpreted as a straight multiplier. The
individual primaries can be changed using -er, -eg and -eb.
Multiple exposure options have a cumulative effect.
-t 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).
-f lampdat
Use the specified lamp lookup table rather than the default
(lamp.tab).
-1 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.
-2 Use two passes on the input. This is the default.
-b Use box filtering (default). Box filtering averages the
input pixels corresponding to each separate output pixel.
-r rad Use Gaussian filtering with a radius of rad 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.
-m frac Limit the influence of any given input pixel to frac 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.
-h lvl Set intensity considered ‘‘hot’’ to lvl. 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.
-n 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.)
-s val Set the spread for star patterns to val. This is the value a
star pattern will have at the edge of the image. The default
is .0001.
-a Average hot spots as well. By default, the areas of the
picture above the hot level are not used in setting the
exposure.
ENVIRONMENT
RAYPATH directories to search for lamp lookup table
FILES
/tmp/rt??????
AUTHOR
Greg Ward
SEE ALSO
getinfo(1), ies2rad(1), pcompos(1), pflip(1), pinterp(1), pvalue(1),
protate(1), rad(1), rpict(1), ximage(1)