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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-lumi- nance] [--help] [--verbose] DESCRIPTION Use this command to convert pixel values to luminance / radiance units dis- played on a monitor or to perform inverse conversion. This command is use- ful 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_man- tiuk08 tone mapping operator (from the pfstmo package). If neither --to-luminance nor --to-pixels option is specified, the appro- priate 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 as- sumes -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 dis- play 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 luxA 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 particu- lar 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 lumi- nance from a distance, such as Minolta LS-100 (as opposed to those that use rubber tube touching a display that eliminates the influ- ence 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 bar- bara_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)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | SEE ALSO | BUGS
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