RDJPGCOM(1)

💖 rdjpgcom — read the vibes (and the text comments) out of your JPEGs 💖

Okay bestie, welcome to rdjpgcom(1), aka the tiny little general-commands-manual icon that reads text comments out of JPEG files. No cap, she's small but she's mighty. 🎀

✨ SYNOPSIS ✨

rdjpgcom [ -raw ] [ -verbose ] [ filename ]

That's it. That's the whole mood. 💅

🌸 DESCRIPTION 🌸

So here's the tea: rdjpgcom reads the JPEG/JFIF file you name — or, if you don't name one at all, it just reads from standard input like a chill little gremlin — and then it prints any text comments it finds in that file to standard output. Simple. Iconic. 🦋

Now let me explain why this is a whole thing. The JPEG standard literally allows "comment" (COM) blocks to just… exist inside a JPEG file. And yeah, the standard doesn't actually define what COM blocks are for, which is lowkey hilarious, but the world collectively decided they're for holding user-supplied text strings. So people use them to stash annotations, titles, index terms, etc. inside their JPEG files, and then later they can pull those back out as text. 🫶

The COM blocks do not interfere with the actual image stored in the JPEG file — like, not even a little bit. And size-wise? The maximum size of a COM block is 64K, but you can have as many of them as you like in one JPEG file. As many as you like, bestie. Go off. 🔥

💅 OPTIONS 💅

• -raw — Normally rdjpgcom escapes non-printable characters in comments, for security reasons (yes, for real, safety first 🛡️). This option avoids that. That's the whole thing.
• -verbose — Causes rdjpgcom to also display the JPEG image dimensions. Extra info, extra slay. ✨

Small but crucial detail: switch names may be abbreviated, and they are not case sensitive. So like, do your thing. 😌

🧚 HINTS 🧚

rdjpgcom does not depend on the IJG JPEG library. Not even a little. Her source code is intended as an illustration of the minimum amount of code required to parse a JPEG file header correctly — like a little educational icon showing you the bare minimum. 🌈

And in -verbose mode, rdjpgcom will also attempt to print the contents of any "APP12" markers as text. Some digital cameras produce APP12 markers containing useful textual information. If you like, you can modify the source code to print other APPn marker types as well. DIY era. 💜

🔍 SEE ALSO 🔍

cjpeg(1), djpeg(1), jpegtran(1), wrjpgcom(1) — the whole friend group. 🫶

👑 AUTHOR 👑

Independent JPEG Group

Okay that's the whole page, bestie, go read some JPEG comments and have the day you deserve 💖

Signing off with love: this was the General Commands Manual page for rdjpgcom, dated 02 April 2009 — mwah 💋