Slim image - recursively optimize images in a directory using Tinify (TinyPNG / TinyJPG). Tracks already-optimized files via extended file attributes, so re-running is cheap and idempotent - no sidecar lockfile.

Install

Run on demand:

npx slimage

Or install globally:

npm i -g slimage

Authenticate

Get a free API key at tinify.com/developers (500 images/month on the free tier). Then:

slimage auth

You'll be prompted to paste your key - input is hidden, so it doesn't end up in shell history. The key is validated against Tinify, then saved to ~/.config/slimage/config.json (mode 0600).

Alternatives:

• TINIFY_KEY=... environment variable
• slimage --key <key> per-invocation

Resolution order: --key → TINIFY_KEY → config file.

Usage

# optimize current directory
slimage

# specific directory
slimage ./public

# preview without uploading
slimage --dry-run

# re-optimize files that have already been processed
slimage --force

# tune concurrency (default 5)
slimage -c 10

Supported formats: JPEG, PNG, WebP. node_modules, .git, dist, build, .next, .cache, and dotfiles are skipped.

How dedupe works

After each successful optimization, slimage writes an extended attribute named user.slimage onto the file containing a content hash and metadata. On the next run, any file whose current hash matches its stored marker is skipped - no API call, no quota burned. Edit the file (which changes its hash) and it'll be picked up again.

If extended attributes aren't supported on your filesystem (rare - FAT32, some network mounts), slimage transparently falls back to a per-root cache file at ~/.cache/slimage/<encoded-path>.json.

Inspecting the marker

# macOS
xattr -p user.slimage path/to/image.png

# Linux
getfattr -n user.slimage path/to/image.png

Clearing the marker

# macOS
xattr -d user.slimage path/to/image.png

# Linux
setfattr -x user.slimage path/to/image.png

Or use --force to ignore markers globally for one run.

License

MIT © Nathaniel Davis