pfsabsolute(1)						      General Commands Manual						    pfsabsolute(1)

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 multi-
       plied  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.

SEE ALSO

       pfsgamma(1) pfsinppm(1)

BUGS

       Please report bugs and comments to Rafal Mantiuk <mantiuk@mpi-sb.mpg.de>.

																    pfsabsolute(1)