pfsabsolute(1)

✨ pfsabsolute ✨

okay bestie, gather round, because this lil cutie from the General Commands Manual is literally the glow-up your images have been waiting for 💖

🌸 NAME 🌸

pfsabsolute — convert luminance in images to absolute measure. that's it, that's the whole job, and she does it flawlessly 💅

🎀 SYNOPSIS 🎀

pfsabsolute <dest Y> [<src Y>] [--verbose] [--help]

🦋 DESCRIPTION 🦋

so here's the tea ☕ — pfsabsolute applies all necessary operations to convert an image from relative luminance (tag LUMINANCE is RELATIVE) or display-dependent luma (tag LUMINANCE is DISPLAY) into absolute luminance values. and when the luminance in an image is already absolute (tag LUMINANCE set to ABSOLUTE), the Y channel represents physical luminance in cd/m^2. absolute luminance levels are genuinely so useful for some tone mapping algorithms, and also for image or video compression. like, iconic behavior tbh 👑

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>. and <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. easy peasy 🍓

and in case of display-depended luma (tag LUMINANCE is DISPLAY), the inverse gamma correction is applied (assuming sRGB color space). in that case <dest Y> is usually the maximum luminance of a display (e.g. 80 cd/m^2). yes bestie, write that down 📝

💀 heads up: this command always sets the LUMINANCE tag to ABSOLUTE. no exceptions, no take-backs, periodt.

🌈 EXAMPLES 🌈

okay now the fun part, let's see her in action ✨

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. she ate that fr fr 🫶

👑 SEE ALSO 👑

• pfsgamma(1)
• pfsinppm(1)

go read those too, iykyk 🧚

🙈 BUGS 🙈

please report bugs and comments to Rafal Mantiuk <mantiuk@mpi-sb.mpg.de>. be nice, be specific, and slay 💌

and that's the whole page bestie!! this one lives in the General Commands Manual as pfsabsolute(1) — no cap, go convert some luminance 💖✨🎀