PNG24PNG32

PNG24 and PNG32 are informal labels used to describe common color depths of PNG images. They refer not to different formats but to the bit depth per pixel: PNG-24 for 24-bit truecolor (three 8-bit channels for red, green, and blue, with no alpha), and PNG-32 for 32-bit truecolor with an alpha channel (RGBA, four 8-bit channels).

In the PNG specification, 24-bit color corresponds to color type 2 (truecolor) with 8-bit samples per channel; 32-bit corresponds to color type 6 (truecolor with alpha). Both use lossless DEFLATE compression, and the choice affects file size primarily through content complexity rather than a different compression method.

PNG-32 enables transparency and compositing; alpha values range from 0 (fully transparent) to 255 (fully opaque), allowing smooth edges and varying translucency. PNG-24 is used when no transparency is needed, such as diagrams or logos on opaque backgrounds.

Practical considerations include broad support across image editors and web browsers for both formats. Some older viewers may ignore alpha in PNG-24, and PNG-32 files can be larger than their 24-bit counterparts or comparable to JPEG in certain photographic cases. PNG remains lossless, making it suitable for images requiring exact reproduction or multiple rounds of editing, particularly with transparency or sharp edges.