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PicCompressor

Fast, local, privacy-friendly JPEG compression for desktop and command line.

About

PicCompressor converts JPEG and PNG images to compact JPEG files using Jpegli. All processing stays on your computer—images are never uploaded.

The desktop application and CLI share the same compression pipeline and safety rules.

Highlights

• Fast Jpegli-based JPEG compression
• Desktop GUI and scriptable CLI
• Single files, batches, and recursive folders
• Drag and drop, clipboard import, cancellation, and retry
• Before/after preview, queue thumbnails, statistics, and update checks
• Configurable quality, chroma subsampling, and progressive encoding
• EXIF privacy and color-profile policies
• Local history and structured diagnostic logs
• Validated temporary output, collision protection, and explicit overwrite behavior
• Human-readable and versioned JSON CLI output

Caution

Replace original JPEG files is an optional setting. The compressed file is fully validated before publication, but once published it permanently replaces the original. PNG inputs are rejected when this option is selected.

Screenshots

Download

Open GitHub Releases and choose either the Windows x64 one-click installer or the portable ZIP. The package contains both the desktop application and CLI.

Warning

PicCompressor is currently in alpha. Release packages are unsigned and may trigger a Windows SmartScreen warning.

Current status

• Windows x64 GUI, CLI, and native Jpegli pipeline are verified.
• Jpegli is the sole encoder. The former Guetzli integration was removed because of its excessive runtime and resource usage.
• A self-contained Linux x64 CLI package can be built and passes its tests; the GUI, macOS, and linux-arm64 packages are planned but not yet verified.
• The application UI supports English and German. The Russian README is documentation only.
• Signing, installation/update rollback tests, and the remaining release-security gates are still open.

Build from source

Requirements for the current Windows development build:

• .NET SDK 10.0.302
• Visual Studio with .NET desktop and C++ desktop workloads
• CMake 3.25 or newer
• PowerShell 7

dotnet build PicCompressor.slnx
dotnet run --project src/PicCompressor.Desktop/PicCompressor.Desktop.csproj

The first build downloads and compiles the pinned Jpegli sources.

CLI

piccompressor <input> [<input> ...] [options]

Example:

piccompressor "C:\Images" --recursive --quality 80 --output-dir "C:\Images\compressed"

Show all options:

piccompressor --help

For scheduled folder scans (for example a NAS task), --state skips unchanged inputs as a successful no-op, --lock prevents overlapping runs, and --stable-for leaves files that are still being uploaded for a later run:

piccompressor /volume1/photo --recursive --output-dir /volume1/photo-compressed \
  --state /var/piccompressor/scan-state.json --lock /var/piccompressor/scan.lock \
  --stable-for 120 --parallelism 2 --timeout 300 --no-history

Docker

--config <path> runs the CLI continuously over any number of watched folders, each with its own output directory, state file and — optionally — its own compression settings. mode selects the trigger: Interval rescans every intervalSeconds, Watch additionally reacts to debounced file system events and still rescans periodically (inotify delivers nothing on mounted SMB/NFS shares). docker stop ends the container in an orderly way; the current job finishes and no unvalidated output is left behind.

The image is published to the GitHub Container Registry and rebuilt on every push to main and on every version tag (.github/workflows/container.yml):

docker pull ghcr.io/diddlik/piccompressor:latest
docker compose -f docker/docker-compose.yml up -d

Available tags: latest (most recent final release), X.Y.Z and X.Y per version tag, and main for the current development state. Docker never updates on its own; pick up a new image with docker compose pull && docker compose up -d — on a schedule, or through the Watchtower service prepared in docker/docker-compose.yml.

Build locally instead of pulling:

docker build -f docker/Dockerfile -t piccompressor .

The image expects the configuration at /config/piccompressor.json, the watched folders below /data and a writable /state for state, lock and log. See docker/piccompressor.example.json for a complete file. Build and run the image with the UID/GID that owns the mounted folders; the container never runs as root. --once runs a single cycle over every folder and exits, which is the way to drive the same configuration from an external scheduler.

Only linux/amd64 is built and verified; linux/arm64 is prepared through TARGETARCH but untested. The container runs the CLI, not the GUI.

License

PicCompressor is licensed under the Apache License 2.0.