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XPAND(9.1)                                                          XPAND(9.1)



NAME
       xpand, picnegate - adjust dynamic range

SYNOPSIS
       fb/xpand [ -s ] [ input ] [ lo hi [ inlo inhi ] ]

       fb/picnegate [ input ]

DESCRIPTION
       Xpand  linearly adjusts the dynamic range of the input picture (default
       standard input) mapping value inlo to lo, and inhi to hi.   Lo  and  hi
       default  to  0 and 255.  If inlo and inhi are not specified, the lowest
       and highest pixel values in the input  image  are  used.   By  default,
       then,  xpand  expands the image's dynamic range by mapping its smallest
       pixel value to zero and its largest value to 255.  Option -s causes all
       channels  of  the  input image to be considered together when computing
       default values for inlo and inhi, thus preserving the hue of  rgb  pic-
       tures.   Otherwise,  each channel is treated separately.  Option -s has
       no effect if inlo and inhi are specified on the command line.

       There is no requirement that lo be smaller than hi,  or  that  inlo  be
       smaller  than  inhi,  nor that any of those values be in the range 0 to
       255.  Output values not in the range 0 to 255 are clamped.   For  exam-
       ple,
            xpand 0 255 255 0
       inverts the pixel values of its input.  For convenience, picnegate is a
       script that executes this command.

SOURCE
       /sys/src/fb/xpand.c

SEE ALSO
       picfile(9.6)



                                                                    XPAND(9.1)