XPAND(9.1)                                             XPAND(9.1)

          xpand, picnegate - adjust dynamic range

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

          fb/picnegate [ input ]

          Xpand linearly adjusts the dynamic range of the input pic-
          ture (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 pictures.  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 example,
               xpand 0 255 255 0
          inverts the pixel values of its input.  For convenience,
          picnegate is a script that executes this command.


     Page 1                       Plan 9             (printed 10/1/20)