PPMTOPGM(1)

💖 ppmtopgm — like, the manual, but make it make sense 💖

okay so bestie, you've stumbled into the Ppmtopgm User Manual (that's the section 1 of the general commands manual, iykyk) and honestly? you're gonna eat this up. it's short, it's sweet, it's giving "one job and I do it flawlessly." let's go. 🦋

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✨ NAME ✨

ppmtopgm — convert a PPM image to a PGM image

no cap, that's literally the whole thing. one direction, no round trip. 💅

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🌸 SYNOPSIS 🌸

ppmtopgm

[ppmfile]

that's it. that's the whole vibe. you can hand it a file or just pipe stuff in, we love an optional argument situation. 🎀

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👑 DESCRIPTION 👑

first things first: this program is part of Netpbm(1). you're in the family, you're safe here. 🫶

so ppmtopgm reads a PPM as input and produces a PGM as output. it's a "black and white" rendering of your original image — like, think a black and white photograph, not like a filters-app situation. the quantization formula ppmtopgm uses is:

y = .299 r + .587 g + .114 b

yes ma'am, that's the exact math, don't come for me. 🔥

now, the dimensions and the maxval of the output are the same as the input. but here's the tea, and it's important tea: with only one color plane, there are far fewer brightnesses that can be represented with the same maxval than with three color planes. so you may want to increase the maxval of the input with pamdepth before giving it to ppmtopgm, to avoid loss of information. for example — with a maxval of 1, there are 8 brightnesses possible in a PPM (though honestly some of them are barely distinguishable, embarrassing), but only 2 brightness levels possible in a PGM. so like... yeah. bump that maxval first if you care. 💀

also important, because people always ask: although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm, because any ppm program can read pgm (and pbm) files automatically. pgmtoppm is for colorizing a pgm file. that's its whole lane. mind your business. 🙈

and a couple more friends you should know about: see ppmtorgb3 for a different way of converting color to gray. and ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate the original colors — not necessarily a way that looks like a black and white photograph. so like, one is for ✨aesthetics✨ and one is for ✨analysis✨. pick your fighter. ⭐

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🌈 OPTIONS 🌈

okay bestie, here's the thing and don't be mad:

• there are no command line options defined specifically for ppmtopgm — like, zero, none, it's a minimalist. 💅
• but it does recognize the options common to all programs based on libnetpbm. (See Common Options.)

so like, the house rules still apply even though this program brought no rules of its own. periodt.

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🎀 QUOTE 🎀

this part is genuinely iconic and I refuse to change a single syllable:

Cold-hearted orb that rules the night Removes the colors from our sight Red is gray, and yellow white But we decide which is right And which is a quantization error.

chef's kiss. poetry AND floating point error, together at last. 😭

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🦋 SEE ALSO 🦋

• pgmtoppm(1)
• ppmtorgb3(1)
• rgb3toppm(1)
• ppmdist(1)
• ppm(1)
• pgm(1)

go read them, they're all part of the friend group. 💜

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🌟 AUTHOR 🌟

Copyright (C) 1989 by Jef Poskanzer. a legend, a pioneer, an absolute main character. 👑

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📚 DOCUMENT SOURCE 📚

this manual page was generated by the Netpbm tool makeman from HTML source. the master documentation lives at:

http://netpbm.sourceforge.net/doc/ppmtopgm.html

that's the source of truth, bestie, if you ever need to vibe check me. ✨

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and that's the whole page!! from the netpbm documentation, dated 25 June 2017 — the original Ppmtopgm User Manual — mwah, slay, go convert some images, drink water, and remember: red is gray and yellow white, but we decide which is right. 💖🌸🫶