How fast is QOI compared to PNG?

QOI is much faster for both encoding and decoding, often by an order of magnitude, though compression ratios are slightly worse. Detailed benchmarks are available at qoiformat.org/benchmark.

How do I convert PNG images to QOI format?

Use the provided qoiconv.c tool from the repository or community converters like Super-QOI-converter for various platforms. On Windows, PowerToys adds Explorer preview support.

Is QOI lossless like PNG?

Yes, QOI is entirely lossless, preserving every pixel exactly as in the original image, making it suitable for applications where quality cannot be compromised.

QOI or JPEG: which is better for web images?

QOI is lossless and faster, ideal for graphics where quality matters. JPEG is lossy and smaller, better for photos where some quality loss is acceptable to save bandwidth.

Can QOI handle transparency in images?

Yes, QOI supports alpha channels for transparency, similar to PNG, so it works well for UI assets, sprites, and other graphics requiring partial opacity.

How to add QOI support to my C++ game engine?

Simply include the qoi.h header file in your project and use the provided functions. Many engines like Raylib and Unity already have community plugins for seamless integration.

Open-Awesome

QOI

MITC

A simple, fast, lossless image format with compression comparable to PNG and a single-file C/C++ library.

GitHub

7.5k stars377 forks0 contributors

What is QOI?

QOI (Quite OK Image Format) is a lossless image compression format and single-file C/C++ library designed for high-speed encoding and decoding. It solves the need for a simple, fast alternative to PNG that maintains reasonable compression ratios without complex dependencies.

Target Audience

Developers and engineers working on graphics applications, game engines, embedded systems, or tools where fast image loading/saving and minimal library footprint are important.

Value Proposition

Developers choose QOI for its exceptional simplicity, speed, and ease of integration—the entire reference implementation is a single header file with no dependencies, making it trivial to drop into projects.

Overview

The “Quite OK Image Format” for fast, lossless image compression

Use Cases

Best For

Fast loading of texture assets in game engines
Embedded systems with limited processing power
Tools requiring simple image I/O without external libraries
Prototyping where PNG complexity is overkill
Applications prioritizing decode/encode speed over maximum compression
Educational projects to understand image format fundamentals

Not Ideal For

Applications where maximum lossless compression ratio is the top priority, such as archival image storage.
Projects that need to handle images larger than 400 million pixels or require streaming en-/decoding without full RAM loading.
Environments demanding built-in, universal format support without relying on third-party libraries or plugins.
Use cases requiring format features like animation, metadata, or progressive loading.

Pros & Cons

Pros

Blazing Fast Performance

QOI encodes and decodes images significantly faster than typical PNG implementations, with benchmarks showing much higher throughput while maintaining comparable compression ratios.

Extreme Simplicity

The entire reference implementation is a single MIT-licensed C header file with no dependencies, making it trivial to integrate into any C/C++ project.

Lossless Quality

Preserves all original image data without any quality degradation, suitable for exact pixel reproduction in graphics and game assets.

Broad Language Support

Has an extensive ecosystem of community bindings for languages from Python to Rust, easing adoption in diverse tech stacks without reinventing the wheel.

Cons

Compression Trade-off

QOI's compression ratio is generally worse than optimized PNG libraries like libPNG, as admitted in the README, leading to larger file sizes in some cases.

RAM-Intensive Reference

The standard implementation loads entire images into memory before processing, preventing streaming and limiting use with very large images exceeding 400 million pixels.

Static Format

The QOI format is finalized with no versioning in the header, meaning it won't evolve to include new features or improvements, as stated in the README.

Less Universal Native Support

Unlike PNG, QOI isn't natively supported in all browsers and operating systems, requiring plugins or custom implementations for broad compatibility.

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