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Portable Network Graphics (.png) is an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed color, grayscale and RGB images are supported, plus an optional alpha channel. Sample depths range from 1 to 64 bits per pixel, supporting up to 48-bit RGB color with a 16-bit alpha channel.[1][2]


PNG is designed for online viewing applications, such as through the web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store gamma correction and chromaticity data for improved color matching on various platforms.[1]

"Minified" PNGs[]

PNGs normally support alpha channels to support transparency at 8 or 16-bits per pixel. However, it is also possible to create a "minified" 8-bit indexed color image with a "cheap" alpha channel; though this format is supported in most modern web browsers, it has not been as widely supported by graphics software.[3][4]

Adobe Fireworks could always export minified PNG very efficiently.[5] Adobe Photoshop added support for importing minified PNGs in 2012 with version CS6.[6] The ability to export minified PNGs came later in a version of Photoshop CC.


  1. 1.0 1.1 Portable Network Graphics at the Free On-Line Dictionary Of Computing. 1997-08-07.
  2. A guide to PNG optimization by Cosmin Truţa, SourceForge. Accessed 2022-01-14.
  3. Chapter 8. PNG Basics: Palette-Based with Transparency by Greg Roelofs, PNG: The Definitive Guide, 2nd ed. O'Reilly & Associates. 2003.
  4. Transparent PNG loses anti-aliasing in Photoshop, StackExchange. 2014-05-19.
  5. Fireworks vs Photoshop Compression by Aigars Silkalns, Web Designer Wall. 2009-10-30.
  6. Photoshop CS5: Opening Indexed Transparent PNG loses transparency by chris_cox_2148894, Adobe Photoshop Family. 2011-07-12.

See also[]

  • SVG (Scalable Vector Graphics), for online vector images.

External links[]

Online PNG tools[]

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