Technical Specifications 1 of 7
Technical Characteristics
PNG is a chunk-based raster image format standardized by the World Wide Web Consortium. It stores a rectangular pixel array using lossless compression and supports grayscale, truecolor, indexed-color, and optional alpha transparency.
A conforming PNG datastream includes:
- The eight-byte PNG signature
- An IHDR image header as the first chunk
- One or more IDAT chunks containing the compressed image datastream
- An IEND chunk marking the end of the datastream
- A PLTE palette when the image uses indexed color
- Optional ancillary chunks for information such as color, transparency, text, physical pixel dimensions, or metadata
PNG technical characteristics
| Characteristic | Specification |
|---|---|
| Standard extension | .png |
| Media type | image/png |
| Image model | Raster pixel array |
| Byte order | Network byte order, most significant byte first |
| Compression | Lossless DEFLATE compression in a zlib datastream |
| Filtering | Per-scanline filtering before compression |
| Interlacing | None or Adam7 |
| Transparency | Alpha channel or transparency information, depending on color type |
| Animation | Supported by the PNG Third Edition APNG structure, but receiving software may vary |
| Integrity checking | CRC for each chunk |