What image format for tiles would you use in your project: bmp or png?

Question

Graphic arts

Good day!
I develop a platformer for the soul, the graphics are based on tiles, I use the tiled editor as an editor, and unity3d as an engine.
The question is: what image format for tiles would you use in your project? Initially, I planned to use bmp, since it is a lossless format, for tiles the size is not very large, about a kilobyte. However, I ran into the fact that due to the lack of transparency in it, unity3d is not able to determine the boundaries for collisions itself and I will have to manually create these boundaries for each tile, so I’m looking towards png, is it worth it?
Thanks for answers!

Answer 1

Unity still converts the textures to its own format when compiling, so the source code can be anything.
But still, PNG32 is better - 1) honest 8-bit transparency, 2) no loss, 3) low weight.
In BMP, you can assign some color to be “transparent” (for example, if you have isometric tiles, then in a square image 4 corners will be painted over, for example, lilac), but this must be supported by the shader and this will be “one-bit” transparency, that is, with the edges of the stairs.