Bug: Texture colors inverted on WASM target

[Zentendo]

@caelunshun Thanks for adding WASM support btw!

Texture colors appear to be inverted on the WASM target, using the latest experimental branch commit 26be4a0:

Native Vulkan target:

Inverted colors with same result on Chrome, Firefox, Edge:

Original texture:

Relevant code:

let mut texBuilder = cx.create_texture_set_builder();
texBuilder.add_texture(include_bytes!("../assets/crab.png"), "sprite1").unwrap();
let texSet = texBuilder.build(1024, 1024).unwrap();
cx.add_texture_set(texSet);

let tex = Context::texture_for_name(canvas.context(), "sprite1").unwrap();
canvas.draw_sprite(tex, vec2(20., 20.), 400.);

[caelunshun]

Thanks for the bug report!

Looks like wgpu doesn't implement BGRA textures on WebGL, so the BGRA texture atlas gets interpreted as RGBA—thus swapping the red and blue channels.

As a workaround, we can use an RGBA format when on the Web.

[Zentendo]

@caelunshun Works, thanks!

#[cfg(target_arch = "wasm32")]
pub fn add_web_texture(
  texBuilder: &mut TextureSetBuilder,
  data: &[u8],
  name: impl Into<String>,
) -> Result<(), image::ImageError> {
  let image = image::load_from_memory(data)?.to_rgba8();
  texBuilder.add_raw_texture(image.width(), image.height(), image.into_raw(), name);
  Ok(())
}