Name
pixfilter — apply a 3x3 filter to a color pix file
Synopsis
pixfilter
[-f type
] [-v ] [-d div
] [-o offset
] [-w width
] [-n height
] [-s squaresize
] [file.pix
] > newfile.pix
DESCRIPTION
pixfilter
applies one of several 3x3 kernel filters to a color
pix(5)
format file.
It will take a file name or else read from standard input.
The input file size will be assumed to be 512 by 512 pixels
unless the
-w
,
and/or
-n
,
or the
-s
flags are used to tell it otherwise.
By default a low pass filter is used. The
-f
type
flag can be used to specify a different type of filter.
The type choices include:
- lo
low pass (the default)
- hi
high pass
- vg
vertical gradient
- hg
horizontal gradient
- la
laplacian
- b
boxcar low pass
Most filters divide the result of the kernel multiplication
by some value in order to scale it back to a 0->255 range.
For example, the boxcar divides by nine. The
-d
flag can be used to change this divisor.
Some filters also add an offset to their results. The output of
a laplacian for example is "centered" about zero, thus it
adds 128 to the answer to yield a difference from neutral grey.
The
-o
flag can be used to change this offset.
The
-v
flag displays the kernel values on standard error.