A game I'm currently researching, has some textures on interface. Those textures in-game are transparent. This game is honestly really old (1999) and those textures are saved as .BMP. Here is a sample texture file:
This game is written in C++.
Here's my question: how is that possible, that a game understands some parts of .BMP, which are definitely black, as a transparent surface? Can you give me an idea, how to define one as well? I'm currently working in canvas (Javascript, BabylonJS), but I need an idea, not code.