Image Optimiser

image-optimiser is a Linux shell utility that losslessly compresses image files in place.

It recursively scans one or more paths, optimises supported files, and prints per-file and total size reduction.

Features

• Lossless optimisation for PNG, JPG, and JPEG
• Recursive directory scanning
• Multiple input paths in one run
• Keeps image metadata and file permissions where supported by the backend tools
• Reports before/after size for each file and for the full run

How It Works

The script delegates optimisation to proven CLI tools:

• PNG -> oxipng
• JPG/JPEG -> jpegoptim

The files are edited in place, so no separate output folder is created.

Requirements

• Linux
• Bash
• find, awk, du, numfmt (usually available in GNU coreutils/findutils)
• oxipng
• jpegoptim

Install Dependencies

Arch Linux:

sudo pacman -S --needed oxipng jpegoptim coreutils findutils gawk

Debian/Ubuntu:

sudo apt update
sudo apt install -y oxipng jpegoptim coreutils findutils gawk

Fedora:

sudo dnf install -y oxipng jpegoptim coreutils findutils gawk

Usage

Make the script executable:

chmod +x optimise-image.sh

Run it with one or more files/directories:

./optimise-image.sh <path> [<path> ...]

Examples:

# Optimise all supported images in a directory tree
./optimise-image.sh ./assets

# Optimise files and directories together
./optimise-image.sh ./assets ./public/logo.png ./screenshots

Output Example

File #1: './assets/logo.png'
Size: 182K -> 156K

File #2: './assets/banner.jpg'
Size: 1.5M -> 1.3M

Finished processing 2 images
Size: 1.7M -> 1.4M

Notes and Limitations

• Only png, jpg, and jpeg files are processed.
• Scanning is recursive for directory inputs.
• Non-existent paths are skipped with an error message.
• Compression is lossless, but always keep backups for critical assets.

Troubleshooting

oxipng: command not found or jpegoptim: command not found

• Install missing dependencies from the Requirements section.

Permission denied

• Ensure the script is executable: chmod +x optimise-image.sh
• Ensure you have write permission for the target files.

No files processed

• Verify your path exists and contains png, jpg, or jpeg files.

Contributing

Contributions are welcome.

Please:

• keep the pull requests focused and consistent with the existing style.
• update the documentation when the behaviour changes.

License

Licensed under the GNU General Public License v3.0 or later. See LICENSE for details.