PNG
A lossless format with full transparency support. Ideal for sharp-edged images like logos and screenshots.
PNG (Portable Network Graphics) is a lossless image format established as a W3C Recommendation in 1996. Developed as a patent-free GIF alternative, it combines lossless compression with transparency support.
PNG uses Deflate (LZ77 + Huffman coding). Row-level filtering (Sub, Up, Average, Paeth) increases redundancy before compression. Being lossless, images can be re-saved indefinitely without degradation.
- Alpha channel: 8-bit alpha enables 256 semi-transparency levels, unlike GIF's binary approach
- Color modes: True color (24/48-bit), grayscale (1-16 bit), indexed (up to 256 colors)
- Interlacing: Adam7 displays progressively across 7 passes
- Gamma correction:
gAMAchunk compensates for cross-display color differences
PNG's weakness is file size - photographs can be several times larger than JPEG. It excels with logos, icons, UI assets, and screenshots with sharp edges. It remains essential as a lossless intermediate format in editing workflows.