phomo

phomo is a free Python utility for creating photographic mosaics from a library of tile images. It suits people comfortable with a command line or Python workflow who want control over tile matching and reuse. Its strongest case is a configurable, local mosaic workflow; users seeking a web-based creation service should look elsewhere.

Overview

The tool recreates a master image by arranging tile images into a grid. You can install it with pip and use it as a Python package, or run the phomo command with a master image and a directory of tiles. That makes it a practical fit for users who already manage images and scripts locally, rather than those who want a browser-based editor.

Key features

phomo compares tile images with regions of the master by their color distributions, then assigns tiles using a linear sum assignment algorithm. The CLI offers greyscale, norm and luv_approx distance metrics, color equalization, and options to match color distributions. These choices give users ways to tune how closely tile colors correspond to the source image, though the project does not claim that one setting is best for every image library.

Image controls include cropping and resizing the master and tile images, converting them to black and white, displaying the grid, and setting how often each tile may appear. Custom tile libraries and tile reuse controls make it possible to shape the composition around a chosen image collection. The output format is PNG.

Greedy tile assignment is a performance option, but it gives up accuracy in exchange for speed. Choose it when processing time matters more than a closer match; for image fidelity, the standard assignment approach is the better fit. CUDA acceleration is available through an extra, but requires both a CUDA-compatible GPU and the CUDA toolkit, so it is not a universal shortcut.

Pricing

phomo is free: its Python package and CLI utility cost nothing. There is no free trial because the software is free, and no paid plan is described. CUDA acceleration is part of an optional extra but depends on compatible GPU hardware and the CUDA toolkit. The package requires Python >=3.9 and <3.13.

Platforms

phomo is listed for Linux, macOS and Windows as a desktop utility. The Python package requires a supported Python version, and CUDA use adds hardware and toolkit requirements. The MIT License permits use under its published open-source terms.

Who it's for

phomo is best for technically comfortable users who have a tile-image collection and want adjustable matching, image preparation controls, and a PNG mosaic from a local workflow. Python users may also value being able to use the package in their own scripts. It is a weaker choice for people who want a guided web tool, paid print ordering, or a workflow that avoids command-line and Python setup.

Pros and cons

• Pros: Free access to both package and CLI makes it possible to build mosaics without a software fee.
• Pros: Multiple distance metrics, color controls, cropping, resizing and tile appearance settings give users meaningful control over matching and composition.
• Pros: Linux, macOS and Windows support broadens its fit for desktop users.
• Cons: Greedy assignment trades matching accuracy for performance, which may undermine image fidelity.
• Cons: CUDA acceleration depends on a compatible GPU and toolkit, limiting its value for users without that setup.
• Cons: The Python version range and command-line workflow make it less suitable for users seeking a turnkey browser experience.

Alternatives

Photo Mosaic Software is a useful place to compare more tools in the category.

Choose AndreaMosaic instead if you want a free option with stated limits of 200 megapixels, 30,000 tiles and 50,000 images, plus mosaic creation and printing features.

Picture Mosaics Online Mosaic Tool suits people who want to create mosaics online for free with an account and pay for downloads, prints or video files.

EasyMoza is another web-based choice, with a free low-resolution download and a listed XL High Resolution option at $595, paid once.

Photo Mosaica is a free alternative for iOS and macOS.

PhotoMosaic.ai is a web option with an always-free lower-resolution plan that supports unlimited mosaic creation and 4,800×4,800px output.

PicTiler is a web service with a free standard-quality option for personal and commercial use.

Rapid-Mosaic is worth considering if you want free Windows software that creates mosaics locally and lets you order prints online.

Mosaic Magnifique is a free Windows alternative.

Verdict

Choose phomo if you want a free, cross-platform Python and command-line tool with adjustable tile matching and image controls. Its central limitation is the technical setup: Python is required, while CUDA adds specific hardware and toolkit needs. For users seeking a browser-led or print-oriented workflow, one of the web services may be a better fit.