There are three forms of PNG format: 8-bit, 24-bit and 32-bit. Among them, 8-bit PNG supports two different forms of transparency, 24-bit PNG does not support transparency, and 32-bit PNG adds 8-bit transparent channels on the basis of 24 bits, so it can display 256 levels of transparency.

Portable network graphics is a lossless compressed bitmap graphics format, which supports three color schemes: index, grayscale, RGB and Alpha channel.