PVRTC RGB same size as RGBA

I’ve been trying to reduce the texture footprint of my project and I stumbled accross this…

Based on the numbers in Unity and the console output from an iOS build, adding an alpha channel to a PVRTC texture doesn’t increase the ammount of memory it takes up?

Just wanted to confirm this and maybe get an explanation as to how this texture compression format works.


Just wanted to confirm this since it s

It’s by design. PVRTC 4bpp, means that it has 4 bits per pixel, no matter whether your texture is with or without Alpha. Check out this spec: http://blog.imgtec.com/powervr/pvrtc-the-most-efficient-texture-compression-standard-for-the-mobile-graphics-world, or this image more specifically which explains the amount of bits per channel:

As you can see when you have alpha your pixel still takes 4 bits, but it has less bits per channel.