--display-function <df-spec>, -d <df-spec>
To adapt tone-mapping to different displays, this operator must be provided a display function.
The display function describes how output luminance of a display changes with pixel values. If no
parameter is given, the command assumes -dfpd=lcd (see Pre-defineddisplay below). There are
several ways to specify the display function:
Gamma-gain-black-ambientdisplaymodel
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-defineddisplaypd=<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 displaytypes 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-tablelut=<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.
--display-size=<size-spec>, -s=<size_spec>
Specifies how large the image appears to a viewer and what is the viewing distance. If no
parameter is given, -sppd=30 is assumed. Since this tone-mapper is global, display size has
moderate effect on the resulting images and thus skipping this parameter should not do much harm.
There are two ways to specify image size:
vres=<lines>:vd=<screen_heights>[:d=<meters>]
vres - screen's vertical resolution in lines, for example 1024.
vd - viewing distance specified as multiplies of screen height. For example if the
display is seen from 0.5m and the height of its screen is 25cm, vd=2.
d - (optional) viewing distance in meters. This is to account for lower eye's
sensitivity for larger viewing distances (although the effect is negligible). By
default -d=0.5 is assumed.
ppd=<pixels_per_visual_degree>[:d=<meters>]
ppd - how many pixels spans one visual degree.
d - (optional) viewing distance in meters. This is to account for lower eye's
sensitivity for larger viewing distances (although the effect is negligible). By
default -d=0.5 is assumed.
--color-saturation <float>, -c <float>
Decrease or increase color saturation after tone mapping. Default value -c=1 attempts to preserve
color appearance of the original image. Use values >1 to increase and <1 to decrease color
saturation.
--contrast-enhancement <float>, -e <float>
By default this tone-mapper attempts to preserve contrast of an input image (-e=1). This parameter
controls whether the contrast of an input image should be enhanced before tone-mapping. For
example -e=1.15 boosts contrast by 15%. Note that if a target display does not offer sufficient
dynamic range, contrast may be enhanced only for selected tone-values (those that dominate in an
image) or not enhanced at all.
--white-y=<float>, -y=<float>
Tells the tone-mapper what luminance level in the input image should be mapped to the maximum
luminance of a display. Since HDR images contain only relative luminance information, tone-mapper
does not know how bright should be the scene. This option is meant to fix this problem by
providing tone-mapper with the information what luminance level in an input image should be
perceived as a diffuse white surface. Default is none, which means that no such mapping will be
enforced and tone-mapper is free to find an optimal brightness for a given image. This is a
recommended setting for HDR images. Setting --white-y could be necessary for dark scenes, which
could be made too bright by the tone-mapper. The value of this parameter can be also passed in
pfsstream as a tag WHITE_Y. pfstools 1.7 and newer sets set this tag automatically for LDR images.
The command line option overrides the value of the pfstream tag.
--fps=<frames-per-second>, -f=<frames-per-second>
Set the frame rate of the input sequence. Default is 25. Currently only 3 values are supported:
25, 30 and 60. This parameter controls temporal filter that makes sure the resulting sequence is
coherent in time. This reduces the likelihood of a visible flicker.
--output-tone-curve=<filename>, -o=<filename>
Write tone-curves to a text file. This option is mainly for debugging purposes, but can be used to
visualize computed tone-curves. The tone-curve data is stored in a comma separated text file
(CSV), consisting of three columns: frame number, log10 of input luminance factor, log10 of the
resulting display luminance, and the pixel value (0-1).
--verbose, -v
Print additional information during program execution.
--quiet, -q
Do not display progress report.
--help, -h
Print list of commandline options.
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