picoptim

Resize and optimise images, in one command. macOS only.

ImageOptim-CLI is excellent at squeezing bytes out of an image — but it cannot change an image's dimensions. That matters, because for most web work the resizing is where the savings actually come from:

4 photos straight off a phone/camera
  6.74 MB  →  0.87 MB   (-87%)

  resize 2268×4032 → 900×1600 ......... -83%
  ImageOptim on top of that ...........  -4%

imgopt does the resample first (with sips, built into macOS, or ImageMagick if you have it) and then hands the results to ImageOptim.

Install

npm install -g picoptim

You also need ImageOptim.app itself — ImageOptim-CLI automates the GUI app, it does not reimplement it:

brew install --cask imageoptim

Optional extras, picked up automatically when present:

| Tool | Why | | --- | --- | | ImageMagick (brew install imagemagick) | Better Lanczos resampling than sips | | ImageAlpha | Lossy PNG via -a | | JPEGmini | Extra JPEG compression via -j |

Usage

imgopt -m 1600                 # longest side ≤ 1600px → ./optimized/
imgopt -w 1200 -o web *.jpg    # max width 1200px → ./web/
imgopt -m 800 -i photos/       # overwrite the originals in photos/
imgopt -p 50                   # scale to 50%
imgopt                         # optimise only, no resizing
imgopt -m 1600 -n              # dry run: show the plan, write nothing

Options

Resize — never upscales an image that is already smaller than the target.

| Flag | Description | | --- | --- | | -m, --max N | Longest side at most N px | | -w, --width N | Max width N px | | -H, --height N | Max height N px | | -p, --percent N | Scale to N% of the original |

Output

| Flag | Description | | --- | --- | | -o, --out DIR | Destination directory (default: ./optimized) | | -i, --in-place | Overwrite the originals — no copy is kept |

Optimisation

| Flag | Description | | --- | --- | | -a, --imagealpha | Enable ImageAlpha (lossy PNG, much smaller) | | -j, --jpegmini | Enable JPEGmini | | -q, --quality MIN-MAX | ImageAlpha quality 0–100 (default 65-80) | | -R, --no-optimize | Resize only, skip ImageOptim |

Other

| Flag | Description | | --- | --- | | -r, --recursive | Include images in subdirectories | | --engine E | sips, magick or auto (default auto) | | -n, --dry-run | Show what would happen, write nothing | | -h, --help / -V, --version | |

Supported formats: JPEG, PNG, GIF, TIFF.

Design notes

Originals are never touched by default. Output goes to ./optimized/. ImageOptim overwrites in place with no undo — combine that with a downscale and the original is gone for good. -i opts into that behaviour explicitly.

No upscaling. An 800px image asked to fit in a 1600px box is left at 800px, rather than being interpolated up to a blurrier, larger file.

Aspect ratio is preserved. -m/-w/-H define a box to fit inside; the scale factor is computed from whichever constraint binds first.

Why not just ImageMagick?

You can absolutely do magick mogrify -resize 1600x1600\> *.jpg. What you don't get is the ImageOptim pass — the lossless zopfli/pngout/jpegoptim work that shaves the last few percent — nor the safe-by-default output directory, the no-upscale rule, or the before/after accounting. imgopt is the two halves wired together with sensible defaults.

Requirements

• macOS (uses sips and drives ImageOptim.app)
• Node.js ≥ 14 (to install via npm)
• ImageOptim.app

License

MIT © Bruno Pinheiro