Can't take transparent screenshots

[amytimed]

Bevy version

0.15.0

What you did

I have this system:

fn add_icon_camera(
    mut commands: Commands,
    mut images: ResMut<Assets<Image>>,
) {
    let size = Extent3d {
        width: 512,
        height: 512,
        ..default()
    };

    // This is the texture that will be rendered to.
    let mut image = Image::new_fill(
        size,
        TextureDimension::D2,
        &[0, 0, 0, 0],
        TextureFormat::Bgra8UnormSrgb,
        //TextureFormat::Rgba8UnormSrgb,
        RenderAssetUsages::default(),
    );
    // You need to set these texture usage flags in order to use the image as a render target
    image.texture_descriptor.usage =
        TextureUsages::TEXTURE_BINDING | TextureUsages::COPY_DST | TextureUsages::RENDER_ATTACHMENT;

    let image_handle = images.add(image);

    let first_pass_layer = RenderLayers::layer(2);

    commands.spawn((
        Camera2d,
        Camera {
            hdr: false,
            target: image_handle.clone().into(),
            clear_color: bevy::render::camera::ClearColorConfig::None,
            viewport: None,
            ..Default::default()
        },

        OrthographicProjection {
            far: 1.,
            near: -10000000.,
            ..OrthographicProjection::default_2d()
        },
        //first_pass_layer.clone(),
        Msaa::Sample4,
        IconCamera,
    ));

    commands.insert_resource(IconCameraImage(image_handle));
}

Then I try screenshot with the image as the target

What went wrong

In the screenshot it always has a black background. I tried ClearColorConfig::Custom(Color::NONE) too, but that just had pitch black screen (wouldn't even show foreground anymore)

I would've expected it to be transparent because there's an alpha channel to the format and because of the clear color