slothshot 用本地 Gemma 4 E4B 為截圖自動命名

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 3: Slow and Steady

What I Built

slothshot renames screenshots after what's in them. Screenshot 2026-10-03 at 08.15.44.png becomes 2026-10-03 railbook-e-ticket-pnr-4421907736.png.

My screenshots folder had 39 files in three naming schemes, because they came over from a Linux laptop: Screenshot from 2026-02-17 19-14-51.png, 2026-04-09_01-26-24.png and the macOS Screenshot 2026-10-17 at 13.34.06.png. None of them said what was in the picture. When I needed one, I opened thumbnails until I found it.

Renaming them by hand would fix that, and I was never going to do it. So now a vision model on my laptop looks at each screenshot and picks a name: the app or site, and the specific thing on screen. The date stays at the front so the folder still sorts by time. It's for me, and for anyone whose Desktop looks like my Screenshots folder.

Demo

Eight made-up screenshots (a failing Go test, a flat group chat about the electricity bill, a UPI payment, a code review, a train ticket, a Grafana-style alert, a poha recipe and a macOS dialog):

The default is a dry run. -apply renames, -undo puts every old name back from a log file in the folder, and -watch 1m keeps it running so each new screenshot gets a name within a minute of me taking it.

It isn't perfect. It spelled SanDisk "sandsik". On the Go test it wrote "test-monthly-rollup-fail" and left out the actual panic, which is what I'd search for. On my own folder it named a black screenshot the-image-provided-is-completely-black, which is accurate. A name that's mostly right is still easier to search than Screenshot 2026-10-16 at 16.30.00.png.

Code

omlahore / slothshot

Renames your screenshots after what's in them, using a local vision model (Gemma 4 on llama.cpp)

slothshot

Renames your screenshots after what's in them. Screenshot 2026-10-03 at 08.15.44.png becomes 2026-10-03 railbook-e-ticket-pnr-4421907736.png, so Finder and Spotlight can find it when you type "pnr" three weeks later.

A local open-weight vision model (Gemma 4 E4B through llama.cpp) looks at each picture. Nothing leaves your machine, which matters because screenshot folders are full of chats, bank pages and login screens.

Run it

You need llama.cpp and Go.

brew install llama.cpp
llama-server -hf ggml-org/gemma-4-E4B-it-GGUF:Q4_0 --port 8092 -c 8192
go install github.com/omlahore/slothshot@latest

slothshot ~/Pictures/Screenshots            # dry run, prints the new names
slothshot -apply ~/Pictures/Screenshots     # renames them
slothshot -undo ~/Pictures/Screenshots      # puts the old names back
slothshot -watch 1m ~/Pictures/Screenshots  # leave it running, new screenshots get named as they land

It only touches files with a default screenshot name: macOS (Screenshot ... at ...), GNOME (Screenshot from ...), Flameshot (2026-04-09_01-26-24.png), Android and CleanShot…

How I Built It

The model is Gemma 4 E4B, Google's open-weight model that takes images, quantized to 4 bits (the Q4_0 GGUF from ggml-org) and served by llama.cpp's llama-server on localhost. The CLI is about 230 lines of Go with one dependency, golang.org/x/image, for resizing.

For each file:

A regex decides whether the name is a default screenshot name (macOS, GNOME, Flameshot, Android, CleanShot). Files it has already renamed have words after the date, so they never match. Running it twice does nothing the second time.
The image is scaled so its long side is 1536 px and sent to llama-server's OpenAI-compatible endpoint with a short prompt: 3 to 6 words, name the app only if its name is on screen, include the specific thing (the error, the merchant and amount, the page title).
Go turns the answer into a slug: lowercase, hyphens, at most six words. If the name is taken, it adds -2. Every rename is appended to .slothshot.tsv.

Two things went wrong first.

Every answer came back empty. Gemma 4 thinks before it answers by default, and with max_tokens at 40 it spent all of them on "Thinking Process: 1. Analyze the Request". Passing chat_template_kwargs: {"enable_thinking": false} turned that off, and answers came back in about a second.

At 1024 px the model read the PNR 4421907736 as 44197736, two digits gone. A wrong PNR in a filename is worse than none, because you search for the right one and it isn't there. At 1536 px it read all ten digits. Each image now takes roughly 2.5 seconds instead of 1.3. A file gets renamed once, so I took the slower, correct version.

Why Does Open Innovation Matter?

I didn't think of my screenshots folder as private until I read the names slothshot proposed for it. There were chats with friends, video calls with other people's faces in them, and a few login pages. Naming those with a hosted API means uploading every one of them, and with -watch on, every new one as well.

With Gemma on llama.cpp none of it leaves the laptop. It works with Wi-Fi off, and there's no per-image bill, so leaving it on to watch the folder costs nothing. The model is a 5 GB file on my disk. When a better open model comes out I change one flag, and if a provider retires this one next year, my copy keeps working.

The Lazy Payoff

I ran it on my real folder in dry-run mode:

It proposed names for 39 screenshots in 1 minute 47 seconds, between 0.6 and 3.8 seconds each, on a 16 GB MacBook Air. I didn't have to watch it.
Doing it by hand means opening each one, working out what it is and typing a name. Call it 30 seconds each, so about 20 minutes. I'd been putting that off since the oldest file, which is from December 2025.
I took 13 screenshots between October 6 and October 17, about one a day. With -watch running from a LaunchAgent (the plist is in the README), each one has a name by the time I go looking for it, and I don't lift a finger.
Finding one meant scrolling thumbnails. After -apply, it's typing "mailbox" or "pnr" into Finder.

Nine of the 39 were screens from the same dashboard, and four of those came out with exactly the same name. -apply numbers them -2, -3 and -4 instead of overwriting anything.

Prize Categories

Best Use of Gemma: slothshot runs Gemma 4 E4B (open weights, GGUF on llama.cpp) for every name it gives.