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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 lu- minance <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 lumi- nance 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 in- verse 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, assum- ing 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)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | BUGS
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