pfsdisplayfunction − Apply display function to color or gray-scale images
pfsdisplayfunction [--display-function <df-spec>] [--to-pixels | --to-luminance] [--help] [--verbose]
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.
Convert pixel values to absolute luminance / radiance units. For RGB images the same display function is applied in each color channel.
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
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:
gamma or exponent of a display function (default 2.2, usually from 1.8 to 2.8)
peak luminance of a display in cd/m^2 (default 100, from 80 for CRTs to 500 or more for newer displays)
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)
reflectivity of a screen (assuming that it is diffuse) (default 0.01, usually about 0.01 (1%) for LCD displays, more for CRTs)
ambient illumination in lux. Typical values are:
Family living room (dim, default)
A brightly lit office
Sunlight on an average day (min.)
Sunlight on an average day (max.)
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.
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.
barbara.jpg | pfsdisplayfunction -l -d pd:crt -v | pfsout
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.
Please report bugs and comments to the pfstools discussion group (http://groups.google.com/group/pfstools).