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README.md
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@ -8,7 +8,7 @@
## Overview
Oxipng is a multithreaded lossless PNG/APNG compression optimizer. It can be used via a command-line
interface or as a library in other Rust programs.
interface or as a library in other Rust programs. It is fast and highly effective.
## Installing
@ -78,6 +78,13 @@ are almost always better or equal to lower levels, this is not guaranteed and it
rare circumstances that a lower level may give a marginally smaller output. Similarly, using Zopfli
compression (`-z`) is not guaranteed to always be better than without.
## APNG support
Oxipng currently only supports limited optimization of animated PNGs (APNGs). It can perform
alpha-optimization, refiltering and recompression of all frames, but all transformations will be
disabled. For best results, it is recommended to use another tool such as
[apngopt](https://sourceforge.net/projects/apng/files/APNG_Optimizer/) prior to running Oxipng.
## Git integration via [pre-commit]
Create a `.pre-commit-config.yaml` file like this, or add the lines after the `repos` map
@ -131,17 +138,13 @@ and specifying the desired ones, for example:
## History
Oxipng began as a complete rewrite of the OptiPNG project,
which was assumed to be dead as no commit had been made to it since March 2014.
(OptiPNG has since released a new version, after Oxipng was first released.)
The name has been changed to avoid confusion and potential legal issues.
The core goal of rewriting OptiPNG was to implement multithreading,
which would be very difficult to do within the existing C codebase of OptiPNG.
Oxipng began in 2015 as a rewrite of the OptiPNG project. The core goal was to implement
multithreading, which would have been very difficult to do within the existing C codebase of OptiPNG.
This also served as an opportunity to choose a more modern, safer language (Rust).
Note that, while similar, Oxipng is not a drop-in replacement for OptiPNG.
If you are migrating from OptiPNG, please check the [help](MANUAL.txt) before using.
However, Oxipng has evolved considerably since then. While some of the options remain similar to
OptiPNG, the architecture and capabilities are now quite different. It is not a drop-in
replacement - if you are migrating from OptiPNG, please check the [help](MANUAL.txt) before using.
## Contributing
@ -157,36 +160,5 @@ Oxipng is open-source software, distributed under the MIT license.
## Benchmarks
Tested Oxipng 9.0.0 (commit `c16519b38b0519988db625913be919d4f0e42f5d`, compiled
on `rustc 1.74.0-nightly (7b4d9e155 2023-09-28)`) against OptiPNG version 0.7.7,
as packaged by Debian unstable, on a Linux 6.5.0-2-amd64 kernel, Intel Core
i7-12700 CPU (8 performance cores, 4 efficiency cores, 20 threads), DDR5-5200
RAM in dual channel configuration.
```
Benchmark 1: ./target/release/oxipng -P ./tests/files/rgb_16_should_be_grayscale_8.png
Time (mean ± σ): 59.6 ms ± 7.7 ms [User: 77.4 ms, System: 3.6 ms]
Range (min … max): 53.3 ms … 89.9 ms 32 runs
Benchmark 2: optipng -simulate ./tests/files/rgb_16_should_be_grayscale_8.png
Time (mean ± σ): 132.4 ms ± 0.8 ms [User: 132.5 ms, System: 0.6 ms]
Range (min … max): 131.8 ms … 134.4 ms 22 runs
Summary
./target/release/oxipng -P ./tests/files/rgb_16_should_be_grayscale_8.png ran
2.22 ± 0.29 times faster than optipng -simulate ./tests/files/rgb_16_should_be_grayscale_8.png
Benchmark 1: ./target/release/oxipng -o4 -P ./tests/files/rgb_16_should_be_grayscale_8.png
Time (mean ± σ): 88.7 ms ± 4.3 ms [User: 270.3 ms, System: 11.0 ms]
Range (min … max): 86.8 ms … 109.4 ms 26 runs
Benchmark 2: optipng -o 4 -simulate ./tests/files/rgb_16_should_be_grayscale_8.png
Time (mean ± σ): 444.9 ms ± 0.3 ms [User: 444.8 ms, System: 0.7 ms]
Range (min … max): 444.4 ms … 445.6 ms 10 runs
Summary
./target/release/oxipng -o4 -P ./tests/files/rgb_16_should_be_grayscale_8.png ran
5.01 ± 0.25 times faster than optipng -o 4 -simulate ./tests/files/rgb_16_should_be_grayscale_8.png
```
An independent benchmark conducted by @demetris is linked here with permission:\
[oxipng and friends: A comparison of PNG optimization tools](https://op111.net/posts/2025/09/png-compression-oxipng-optipng-fileoptimizer-cwebp/)