Portable Network Graphics

What is PNG?

PNG is a lossless image format that was created to improve upon and replace the GIF format. It supports transparency through an alpha channel, making it ideal for images that need to blend seamlessly with different backgrounds.

Unlike JPEG, PNG compression is completely lossless, meaning the image quality remains perfect even after multiple edits and saves. This makes it the preferred format for graphics, logos, screenshots, and any image requiring crisp edges.

History

PNG was developed in 1995 as a free alternative to the GIF format after Unisys enforced patent licensing for the LZW compression algorithm.

• 1995: PNG development begins
• 1996: PNG 1.0 specification released
• 1998: Becomes ISO standard
• 2004: Full browser support achieved

Key Features

• Lossless Compression: No quality loss
• Alpha Transparency: 256 levels
• 24/48-bit Color: Millions of colors
• Gamma Correction: Color matching
• Interlacing: Progressive display
• Patent-Free: No licensing restrictions

Common Uses

• Logos and brand graphics
• Web graphics and UI elements
• Screenshots
• Images with text or sharp edges
• Graphics requiring transparency
• Icons and interface elements

Advantages

• Perfect quality preservation
• Transparency support
• No quality loss on re-save
• Great for text and sharp edges
• Wide software support

Limitations

• Larger file sizes than JPEG for photos
• No CMYK support for print
• No native animation support
• Can be very large for complex images

Technical Information

PNG uses DEFLATE compression algorithm for lossless data compression. The format supports indexed color, grayscale, and true color images, plus an optional alpha channel for transparency.