1pfsdisplayfunction(1)       General Commands Manual      pfsdisplayfunction(1)
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NAME

6       pfsdisplayfunction  -  Apply  display  function  to color or gray-scale
7       images
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SYNOPSIS

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

14       Use  this command to convert pixel values to luminance / radiance units
15       displayed on a monitor or to perform inverse conversion.  This  command
16       is  useful  in  combination  with  the HDR-VDP to convert LDR images to
17       luminance maps representing images shown on a particular  display.  The
18       display  function  specification is identical to the specification used
19       in the pfstmo_mantiuk08 tone mapping operator (from  the  pfstmo  pack‐
20       age).
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22       If  neither  --to-luminance  nor  --to-pixels  option is specified, the
23       appropriate conversion direction will be deducted  from  the  LUMINANCE
24       tag in the pfs stream.
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OPTIONS

27       --to-luminance, -l
28              Convert pixel values to absolute luminance / radiance units. For
29              RGB images the same display function is applied  in  each  color
30              channel.
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32       --to-pixels, -p
33              Convert absolute luminance / radiance units to pixel values. For
34              RGB images the same display function is applied  in  each  color
35              channel.
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37       --display-function <df-spec>, -d <df-spec>
38              The display function describes how output luminance of a display
39              changes with pixel values. If no parameter is given, the command
40              assumes  -df pd=lcd  (see  Pre-defined display below). There are
41              several ways to specify the display function:
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43       Gamma-gain-black-ambient display model
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45              g=<float>:l=<float>:b=<float>:k=<float>:a=<float>[:n=<float>]
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47              Gamma-gain-black-ambient model can approximate a range  of  dis‐
48              plays  and  is  a  compact way to specify a display function. It
49              assumes that a display function has the following form:
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51              L_d(I) = (l-b)*I^gamma + b + k/pi*a
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53              The parameters are as follows:
54              g -  gamma or exponent of a display function (default 2.2,  usu‐
55                   ally from 1.8 to 2.8)
56              l -  peak  luminance  of a display in cd/m^2  (default 100, from
57                   80 for CRTs to 500 or more for newer displays)
58              b -  black level, which is luminance of a black pixel  when  the
59                   display is on (default 1, usually from 0.3 to 1 cd/m^2)
60              k -  reflectivity  of  a  screen  (assuming  that it is diffuse)
61                   (default 0.01, usually about 0.01 (1%)  for  LCD  displays,
62                   more for CRTs)
63              a -  ambient illumination in lux. Typical values are:
64                   50 lux Family living room (dim, default)
65                   400 lux
66                          A brightly lit office
67                   32000 lux
68                          Sunlight on an average day (min.)
69                   100000 lux
70                          Sunlight on an average day (max.)
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72       Pre-defined display
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74              pd=<display_type>
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76              Use  pre-defined  display type. This options are for convenience
77              only and they do not mean to accurately model the response of  a
78              particular display.  The following display types are recognized:
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80              lcd_office (g=2.2, l=100, b=0.8, k=0.01, a=400 )
81                     lcd set to "office" mode seen in bright environment
82              lcd        (g=2.2, l=200, b=0.8, k=0.01, a=60  )
83                     typical lcd seen in dim environment (default)
84              lcd_bright (g=2.6, l=500, b=0.5, k=0.01, a=10  )
85                     newer LCD TV seen in dark environment
86              crt        (g=2.2, l=80,  b=1,   k=0.02, a=60  )
87                     CRT monitor seen in dim environment
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89              The parameters in the parenthesis are the same as for the gamma-
90              gain-black-ambient model explained above.
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92       Lookup-table
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94              lut=<file>
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96              This is the most accurate specification of the display  response
97              function,  but requires measuring it with a luminance meter. The
98              lookup table should account also for ambient light, so  that  it
99              is  recommended  to  use  the  luminance  meter that can measure
100              screen luminance from a distance, such  as  Minolta  LS-100  (as
101              opposed  to  those  that use rubber tube touching a display that
102              eliminates the influence of ambient light). The <file> must be a
103              comma-separated  text  file  in a format (CSV) with two columns:
104              first column represents pixel values (from 0.0 to 1.0)  and  the
105              second  physical  luminance  in cd/m^2. Both the pixel value and
106              the luminance should increase in each raw.
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EXAMPLES

109       pfsin barbara.jpg | pfsdisplayfunction -l -d pd:crt -v  |  pfsout  bar‐
110       bara_crt.hdr
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112              Convert  barbara.jpg  image from pixel values to a luminance map
113              of the image shown on a CRT monitor and store the map as an  HDR
114              image.
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SEE ALSO

117       pfsgamma(1) pfstmo_mantiuk08(1)
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BUGS

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