pfsdisplayfunction(1)					      General Commands Manual					     pfsdisplayfunction(1)

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 com-
       mand 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 chan-
	      nel.

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

       --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 par-
	      ticular 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 repre-
	      sents 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)