Batch resize and convert photos with ImageMagick

Pick a folder of photos and run ImageMagick 7 on every one of them: shrink them for the web, make thumbnails, convert to WebP or PNG, or recompress JPEGs. The unmodified ImageMagick program runs inside this tab on a RISC-V virtual machine; your photos are never uploaded.

What you can do

mkdir -p out && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; h=; set -- $(magick identify -format '%w %h ' "$f"); { [ "$1" -gt 1600 ] || [ "$2" -gt 1600 ]; } && h="-define jpeg:size=1600x1600"; magick $h "$f" -auto-orient -strip -resize 1600x1600'>' -quality 82 out/"${f%.*}".jpg || st=1; done; exit $st

mkdir -p out/thumbs && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; h=; set -- $(magick identify -format '%w %h ' "$f"); { [ "$1" -gt 800 ] || [ "$2" -gt 800 ]; } && h="-define jpeg:size=800x800"; magick $h "$f" -auto-orient -strip -thumbnail 800x800'>' -quality 80 out/thumbs/"${f%.*}".jpg || st=1; done; exit $st

mkdir -p out && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; h=; set -- $(magick identify -format '%w %h ' "$f"); { [ "$1" -gt 1600 ] || [ "$2" -gt 1600 ]; } && h="-define jpeg:size=1600x1600"; magick $h "$f" -auto-orient -strip -resize 1600x1600'>' -define webp:method=0 -quality 80 out/"${f%.*}".webp || st=1; done; exit $st

mkdir -p out && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; h=; set -- $(magick identify -format '%w %h ' "$f"); { [ "$1" -gt 1600 ] || [ "$2" -gt 1600 ]; } && h="-define jpeg:size=1600x1600"; magick $h "$f" -auto-orient -strip -resize 1600x1600'>' out/"${f%.*}".png || st=1; done; exit $st

mkdir -p out && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; magick "$f" -auto-orient -strip -quality 80 out/"${f%.*}".jpg || st=1; done; exit $st

st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; magick identify "$f" || st=1; done; exit $st

How it works

1. Pick a folder. Choose the folder with your photos (JPEG, PNG or WebP). They are copied into a sandbox in this browser tab, not uploaded.
2. Choose a preset. Resize for the web, make thumbnails, convert to WebP or PNG, or recompress JPEGs. Set the size and quality; the magick command appears and can be edited.
3. Run ImageMagick. Press Run. ImageMagick processes one photo after another and writes the results into an out/ folder; the output pane shows each file as it starts.
4. Save the results. Save out/ back into your folder, or download it as a zip file.

Under the hood the page boots NanoVM, a Linux userland compiled to WebAssembly, in this tab. Your folder is copied into its in-memory filesystem at /work, and a BusyBox shell runs the command, which starts magick on the RISC-V runner. The Terminal tab opens the same folder in an interactive shell, for anything the presets don’t cover.

Your files stay on your device

Your photos are read by your browser and copied into an in-memory filesystem inside this tab, where the ImageMagick program runs on NanoVM's RISC-V emulator. Nothing is uploaded; there is no server that could receive them.

The presets remove EXIF metadata (including GPS location) from the images they write, and apply the camera's rotation first so nothing ends up sideways.

The only network requests are for the ImageMagick program itself: a signed, content-hashed package from the jsDelivr CDN, fetched once and cached. The counter next to the Run button lists every request that leaves this site.

Questions

The software

program

ImageMagick 7.1.2-33

license

ImageMagick License

source

github.com/ImageMagick/ImageMagick

runs on

the RISC-V VM (static Linux binary)

delivered as

a signed, content-addressed package from the NanoVM app catalog (Ed25519 + SHA-256, verified in the browser)

this page

AGPL-3.0-only OR LicenseRef-UEL · source

Build the same thing into your page

This tool is the <nano-tool> web component from the public NanoVM SDK (@userland-run/nano-sdk/tools), with the built-in imagemagick definition. The same element runs on any page:

<script type="module">
  import { defineNanoTool } from "@userland-run/nano-sdk/tools";
  defineNanoTool();
</script>
<nano-tool tool="imagemagick" wasm-url="/nano.wasm" terminal url-params></nano-tool>

Or headless, with the folder bridge (@userland-run/nano-sdk/folder). Definitions are plain data — presets, form fields and quoted command templates — so you can write one for any catalog app.

import { createNano } from "@userland-run/nano-sdk";
import { mountFolder } from "@userland-run/nano-sdk/folder";
import { runTool } from "@userland-run/nano-sdk/tools";

const nano = await createNano({ image: { wasm: "/nano.wasm" }, ramMB: 1024 });
const dir = await showDirectoryPicker({ mode: "readwrite" });
const folder = await mountFolder(nano, dir, { at: "/work" });
// installs imagemagick from the signed catalog, then runs:
// mkdir -p out && st=0; for f in *.[jJ][pP]*[gG] *.[pP][nN][gG] *.[wW][eE][bB][pP]; do [ -e "$f" ] || continue; echo "$f"; h=; set -- $(magick identify -format '%w %h ' "$f"); { [ "$1" -gt 1600 ] || [ "$2" -gt 1600 ]; } && h="-define jpeg:size=1600x1600"; magick $h "$f" -auto-orient -strip -resize 1600x1600'>' -quality 82 out/"${f%.*}".jpg || st=1; done; exit $st
const r = await runTool(nano, { tool: "imagemagick", preset: "web", folder });
if (r.exitCode === 0) await folder.writeBack(); // new and changed files only; never deletes

More tools

• Photo metadata removerStrip GPS location, camera and date metadata from a folder of JPEG, PNG, WebP and HEIC photos.
• PDF toolsMerge, split, optimize and password-protect a folder of PDFs with pdfcpu.
• CSV SQL queryJoin, filter and group CSV files with SQL — every CSV becomes a SQLite table.

← All tools