RGBA color model
Appearance
RGBA color space stands for Red Green Blue Alpha.
Alpha is the transparency channel, and is unique to this color space. The alpha is often called alpha transparency.
RGBA, like RGB, is an additive color space, so the more of a color you place, the lighter the picture gets.
PNG is the best known image format that uses the RGBA color space.
External Link
- Alpha transparency on W3C PNG specification