OptiPNG – advanced PNG optimizer

OptiPNG is a PNG optimizer that recompresses image files to a smaller size, without losing any information. This program also converts external formats (BMP, GIF, PNM and TIFF) to optimized PNG, and performs PNG integrity checks, corrections, metadata recovery and pixmap-to-PNG conversion.

OptiPNG optimizes PNG files, i.e. reduce their size to a minimum, without losing semantic information. In addition, this program shall perform a suite of auxiliary functions like integrity checks,

The optimization attempts are not guaranteed to succeed. Valid PNG files that cannot be optimized by this program are normally left intact; their size will not grow. The user may request to override this default behavior.

Features include:

• Lossless compression tool for PNG images. It can also convert non-PNG files (BMP, GIF, PNM and TIFF) into compressed PNG file.
• Encoding and optimization options:
  • Select the optimization level:
    • The optimization level 0 enables a set of optimization operations that require minimal effort. There will be no changes to image attributes like bit depth or color type, and no recompression of existing IDAT datastreams.
    • The optimization level 1 enables a single IDAT compression trial. The trial chosen is what OptiPNG thinks it’s probably the most effective.
    • The optimization levels 2 and higher enable multiple IDAT compression trials; the higher the level, the more trials.
  • Filters – select the PNG delta filters. The filter values 0, 1, 2, 3 and 4 indicate static filtering, and correspond to the standard PNG filter codes (None, Left, Up, Average and Paeth, respectively). The filter value 5 indicates adaptive filtering, whose effect is defined by the libpng library used by OptiPNG.
  • Other options are available.
•  Error recovery.
• Simulation mode – performs the trials but doesn’t create output files.

Website: optipng.sourceforge.net
Support:
Developer: Cosmin Truta and contributors
License: zlib license

OptiPNG is written in C. Learn C with our recommended free books and free tutorials.

Return to Command-Line Image Compression Tools

Popular series
	The largest compilation of the best free and open source software in the universe. Each article is supplied with a legendary ratings chart helping you to make informed decisions.
	Hundreds of in-depth reviews offering our unbiased and expert opinion on software. We offer helpful and impartial information.
	The Big List of Active Linux Distros is a large compilation of actively developed Linux distributions.
	Replace proprietary software with open source alternatives: Google, Microsoft, Apple, Adobe, IBM, Autodesk, Oracle, Atlassian, Corel, Cisco, Intuit, and SAS.
	Awesome Free Linux Games Tools showcases a series of tools that making gaming on Linux a more pleasurable experience. This is a new series.
	Machine Learning explores practical applications of machine learning and deep learning from a Linux perspective. We've written reviews of more than 40 self-hosted apps. All are free and open source.
	New to Linux? Read our Linux for Starters series. We start right at the basics and teach you everything you need to know to get started with Linux.
	Alternatives to popular CLI tools showcases essential tools that are modern replacements for core Linux utilities.
	Essential Linux system tools focuses on small, indispensable utilities, useful for system administrators as well as regular users.
	Linux utilities to maximise your productivity. Small, indispensable tools, useful for anyone running a Linux machine.
	Surveys popular streaming services from a Linux perspective: Amazon Music Unlimited, Myuzi, Spotify, Deezer, Tidal.
	Saving Money with Linux looks at how you can reduce your energy bills running Linux.
	Home computers became commonplace in the 1980s. Emulate home computers including the Commodore 64, Amiga, Atari ST, ZX81, Amstrad CPC, and ZX Spectrum.
	Now and Then examines how promising open source software fared over the years. It can be a bumpy ride.
	Linux at Home looks at a range of home activities where Linux can play its part, making the most of our time at home, keeping active and engaged.
	Linux Candy reveals the lighter side of Linux. Have some fun and escape from the daily drudgery.
	Getting Started with Docker helps you master Docker, a set of platform as a service products that delivers software in packages called containers.
	Best Free Android Apps. We showcase free Android apps that are definitely worth downloading. There's a strict eligibility criteria for inclusion in this series.
	These best free books accelerate your learning of every programming language. Learn a new language today!
	These free tutorials offer the perfect tonic to our free programming books series.
	Linux Around The World showcases usergroups that are relevant to Linux enthusiasts. Great ways to meet up with fellow enthusiasts.
	Stars and Stripes is an occasional series looking at the impact of Linux in the USA.