While programming something in Rust with the BevyEngine, I came across TextureFormats. My understanding is that those are used to define how the pixel data is handled. So Rgba8Unorm means that there are is a red, green, blue and alpha channel. Each of them is represented by an 8bit unsigned integer.

Since I only need a black/white image I read through this list of available TextureFormats in the BevyEngine. But all the "one channel formats" have only one channel for red. Also here in the wgpu-rs crate. There are so many formats with only one channel for red.

Why is that. What is the purpose of having only the red channel. And why am I not abled to find a format that allows me to represent only B/W values. (Is that maybe an "alpha only" format?)


1 Answer 1


Red is the gray scale channel (black/white). To generate a gray scale image copy the Red channel to the Green and Blue channels, set alpha to one and a gray scale image will result.

Of course that single channel can be used for many other purposes besides just gray scale image data. It can represent noise, a lookup table (LUT). The list is long and mighty.

  • $\begingroup$ So its the red channel just because it is the first in the classic rgb scheme? $\endgroup$
    – Voß
    Commented Jul 30, 2021 at 12:10
  • $\begingroup$ Yes, sometimes it is better to think of them as data channels and the r,g,b,a values are just the names. $\endgroup$
    – pmw1234
    Commented Jul 30, 2021 at 12:37

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