pyoxipng 6.0.0

Python wrapper for multithreaded .png image file optimizer oxipng

pyoxipng

Python wrapper for multithreaded .png image file optimizer oxipng (written in Rust). Use pyoxipng to reduce the file size of your PNG images.

Jump to a section

• Installation
• Usage
• Options
  • alphas
  • strip
  • deflate
• Development
• License

Installation

Install from PyPI:

pip install pyoxipng

Import in your Python code:

import oxipng

Usage

To optimize an existing file on disk:

oxipng.optimize("/path/to/image.png", "/path/to/image-optimized.png")

Second argument is optional; if not provided, will overwrite the existing file.

To optimize a file already-loaded in Python as a bytes object:

data = ...  # bytes of png data

optimized_data = oxipng.optimize_from_memory(data)

# Save the result
with open("/path/to/image-optimized.png", "wb") as f:
    f.write(optimized_data)

Both functions raise oxipng.PngError if the optimization cannot be completed.

Options

Both the optimize and optimize_from_memory functions accept the following options as keyword arguments.

Example usage:

oxipng.optimize("/path/to/image.png", level=6, backup=True, interlace=1)

Option	Description	Type	Default
level	Set the optimization level to an integer between 0 and 6 (inclusive)	int	2
backup	Whether the input file should be backed up before writing the output	bool	False
fix_errors	Attempt to fix errors when decoding the input file rather than throwing PngError	bool	False
pretend	Don't actually write any output file, just calculate the best results	bool	False
force	Write to output even if there was no improvement in compression	bool	False
preserve_attrs	Ensure the output file has the same permissions as the input file	bool	False
filter	Which filters to try on the file [0-5]	set[int]	{0,5}
interlace	Whether to change the interlacing type of the file. 0 means disable interlacing. 1 means enable it. None means leave as is.	int | None	None
alphas	Alpha filtering strategies to use. Use enum values from oxipng.AlphaOptim	set[AlphaOptim]	{AlphaOptim.NoOp}
bit_depth_reduction	Whether to attempt bit depth reduction	bool	True
color_type_reduction	Whether to attempt color type reduction	bool	True
palette_reduction	Whether to attempt palette reduction	bool	True
grayscale_reduction	Whether to attempt grayscale reduction	bool	True
idat_recoding	If any type of reduction is performed, IDAT recoding will be performed regardless of this setting	bool	True
strip	Which headers to strip from the PNG file, if any. Specify with oxipng.Headers	Headers	Headers.none()
deflate	Which DEFLATE algorithm to use. Specify an instance of oxipng.Zlib, oxipng.Zopfli or oxipng.Libdeflater	Zlib | Zopfli | Libdeflater	Zlib()
use_heuristics	Whether to use heuristics to pick the best filter and compression. Intended for use with level=1	bool	False
timeout	Maximum amount of time to spend (in milliseconds) on optimizations. Further potential optimizations are skipped if the timeout is exceeded.	int | None	None

alphas

Initialize the alphas set with any of the following enum options:

• oxipng.AlphaOptim.NoOp
• oxipng.AlphaOptim.Black
• oxipng.AlphaOptim.White
• oxipng.AlphaOptim.Up
• oxipng.AlphaOptim.Right
• oxipng.AlphaOptim.Down
• oxipng.AlphaOptim.Left

strip

Initialize the strip option by calling one of the following static methods provided by the oxipng.Headers class.

Method	Description
oxipng.Headers.none()	None
oxipng.Headers.strip(list[str])	Remove specific chunks
oxipng.Headers.safe()	Headers that won't affect rendering (all but cHRM, gAMA, iCCP, sBIT, sRGB, bKGD, hIST, pHYs, sPLT)
oxipng.Headers.keep(set[str])	Remove all non-critical chunks except these
oxipng.Headers.all()	All non-critical headers

deflate

Initialize the deflate option by instantiating one of the following classes:

• Zlib(compression: list[int] = [9], strategies: list[int] = [0, 1, 2, 3], window: int = 15)
  • compression: Which zlib compression levels to try on the file (1-9)
  • strategies: Which zlib compression strategies to try on the file (0-3)
  • window: Window size to use when compressing the file, as 2^window bytes (8-15). Doesn't affect compression but may affect speed and memory usage
• Zopfli(iterations: int)
  • iterations: The number of compression iterations to do.
• Libdeflater()

Examples:

oxipng.optimize("in.png", deflate=Zlib(compression=[7, 8], window=8))
oxipng.optimize("in.png", deflate=Zopfli(3))
oxipng.optimize("in.png", deflate=Libdeflater())

Development

1. Install Rust
2. Install Python 3.7+
3. Install Pipenv
4. Clone this repository and navigate to it via command line

   git clone https://github.com/nfrasser/pyoxipng.git
   cd pyoxipng
   

5. Install dependencies

   pipenv install --dev
   

6. Activate the dev environment

   pipenv shell
   

7. Build

   maturin develop
   

8. Run tests

   pytest
   

9. Format code

   black .
   

License

MIT