This is the command pfsabsolute that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
pfsabsolute - Convert luminance in images to absolute measure
SYNOPSIS
pfsabsolute <dest Y> [<src Y>] [--verbose] [--help]
DESCRIPTION
pfsabsolute applies all necessary operations to convert an image from relative luminance
(tag LUMINANCE is RELATIVE) or display-dependent luma (tag LUMINANCE is DISPLAY) to
absolute luminance values. When the luminance in an image is absolute (tag LUMINANCE set
to ABSOLUTE), the Y channel represents physical luminance in cd/m^2. Absolute luminance
levels are useful for some tone mapping algorithms and also for image or video
compression.
The argument <dest Y> denotes the level of luminance that relative luminance <src Y>
should be rescaled to. The luminance is in fact multiplied by the ratio <dst Y>/<src Y>.
<src Y> is normally relative luminance checked with pfsview in the spot where the absolute
luminance <dest Y> is measured, known or guessed. If <src Y> is omitted, the value 1 is
assumed, so <dest Y> is just a scaling factor.
In case if display-depended luma (tag LUMINANCE is DISPLAY), the inverse gamma correction
is applied (assuming sRGB color space). In such case <dest Y> is usually the maximum
luminance of a display (e.g. 80 cd/m^2).
This command always sets LUMINANCE tag to ABSOLUTE.
EXAMPLES
pfsin memorial.hdr | pfsabsolute 20 0.04 | pfsview
Multiply luminance in memorial image, so that relative luminance 0.04 becomes 20
cd/m^2. Normally, the value 0.04 is check using pfsview in the spot, where the
absolute luminance (which equals in this case 20 cd/m^2) is known.
pfsin lena.png | pfsabsolute 80 | pfsview
Convert lena image from sRGB color space to absolute XYZ, assuming maximum
luminance of the monitor 80 cd/m^2.
Use pfsabsolute online using onworks.net services
