NAME

       pfsdisplayfunction - Apply display function to color or gray-scale images

SYNOPSIS

       pfsdisplayfunction  [--display-function <df-spec>] [--to-pixels | --to-luminance] [--help]
       [--verbose]

DESCRIPTION

       Use this command to convert pixel values to luminance /  radiance  units  displayed  on  a
       monitor  or  to perform inverse conversion. This command is useful in combination with the
       HDR-VDP to convert LDR images to luminance maps representing images shown on a  particular
       display.  The display function specification is identical to the specification used in the
       pfstmo_mantiuk08 tone mapping operator (from the pfstmo package).

       If neither --to-luminance nor --to-pixels option is specified, the appropriate  conversion
       direction will be deducted from the LUMINANCE tag in the pfs stream.

OPTIONS

       --to-luminance, -l
              Convert  pixel  values  to  absolute luminance / radiance units. For RGB images the
              same display function is applied in each color channel.

       --to-pixels, -p
              Convert absolute luminance / radiance units to pixel values.  For  RGB  images  the
              same display function is applied in each color channel.

       --display-function <df-spec>, -d <df-spec>
              The display function describes how output luminance of a display changes with pixel
              values. If no parameter is given, the command assumes -df pd=lcd  (see  Pre-defined
              display below). There are several ways to specify the display function:

       Gamma-gain-black-ambient display model

              g=<float>:l=<float>:b=<float>:k=<float>:a=<float>[:n=<float>]

              Gamma-gain-black-ambient model can approximate a range of displays and is a compact
              way to specify a display function. It assumes  that  a  display  function  has  the
              following form:

              L_d(I) = (l-b)*I^gamma + b + k/pi*a

              The parameters are as follows:
              g -  gamma or exponent of a display function (default 2.2, usually from 1.8 to 2.8)
              l -  peak  luminance  of a display in cd/m^2  (default 100, from 80 for CRTs to 500
                   or more for newer displays)
              b -  black level, which is luminance of a  black  pixel  when  the  display  is  on
                   (default 1, usually from 0.3 to 1 cd/m^2)
              k -  reflectivity  of a screen (assuming that it is diffuse) (default 0.01, usually
                   about 0.01 (1%) for LCD displays, more for CRTs)
              a -  ambient illumination in lux. Typical values are:
                   50 lux Family living room (dim, default)
                   400 lux
                          A brightly lit office
                   32000 lux
                          Sunlight on an average day (min.)
                   100000 lux
                          Sunlight on an average day (max.)

       Pre-defined display

              pd=<display_type>

              Use pre-defined display type. This options are for convenience only and they do not
              mean  to  accurately  model  the  response  of a particular display.  The following
              display types are recognized:

              lcd_office (g=2.2, l=100, b=0.8, k=0.01, a=400 )
                     lcd set to "office" mode seen in bright environment
              lcd        (g=2.2, l=200, b=0.8, k=0.01, a=60  )
                     typical lcd seen in dim environment (default)
              lcd_bright (g=2.6, l=500, b=0.5, k=0.01, a=10  )
                     newer LCD TV seen in dark environment
              crt        (g=2.2, l=80,  b=1,   k=0.02, a=60  )
                     CRT monitor seen in dim environment

              The parameters in the parenthesis are the same as for the  gamma-gain-black-ambient
              model explained above.

       Lookup-table

              lut=<file>

              This  is  the  most  accurate  specification  of the display response function, but
              requires measuring it with a luminance meter. The lookup table should account  also
              for  ambient  light,  so that it is recommended to use the luminance meter that can
              measure screen luminance from a distance, such as Minolta  LS-100  (as  opposed  to
              those  that  use  rubber  tube  touching a display that eliminates the influence of
              ambient light). The <file> must be a comma-separated text file in  a  format  (CSV)
              with  two  columns:  first column represents pixel values (from 0.0 to 1.0) and the
              second physical luminance in cd/m^2. Both the pixel value and the luminance  should
              increase in each raw.

EXAMPLES

       pfsin barbara.jpg | pfsdisplayfunction -l -d pd:crt -v  | pfsout barbara_crt.hdr

              Convert  barbara.jpg  image from pixel values to a luminance map of the image shown
              on a CRT monitor and store the map as an HDR image.

SEE ALSO

       pfsgamma(1) pfstmo_mantiuk08(1)

BUGS

       Please   report    bugs    and    comments    to    the    pfstools    discussion    group
       (http://groups.google.com/group/pfstools).

                                                                            pfsdisplayfunction(1)