bevy/crates/bevy_render/src/texture/hdr_texture_loader.rs

use crate::texture::{Image, TextureFormatPixelInfo};
use anyhow::Result;
use bevy_asset::{AssetLoader, LoadContext, LoadedAsset};
use bevy_utils::BoxedFuture;
use wgpu::{Extent3d, TextureDimension, TextureFormat};

/// Loads HDR textures as Texture assets
#[derive(Clone, Default)]
pub struct HdrTextureLoader;

impl AssetLoader for HdrTextureLoader {
    fn load<'a>(
        &'a self,
        bytes: &'a [u8],
        load_context: &'a mut LoadContext,
    ) -> BoxedFuture<'a, Result<()>> {
        Box::pin(async move {
            let format = TextureFormat::Rgba32Float;
            debug_assert_eq!(
                format.pixel_size(),
                4 * 4,
                "Format should have 32bit x 4 size"
            );

            let decoder = image::codecs::hdr::HdrDecoder::new(bytes)?;
            let info = decoder.metadata();
            let rgb_data = decoder.read_image_hdr()?;
            let mut rgba_data = Vec::with_capacity(rgb_data.len() * format.pixel_size());

            for rgb in rgb_data {
                let alpha = 1.0f32;

                rgba_data.extend_from_slice(&rgb.0[0].to_ne_bytes());
                rgba_data.extend_from_slice(&rgb.0[1].to_ne_bytes());
                rgba_data.extend_from_slice(&rgb.0[2].to_ne_bytes());
                rgba_data.extend_from_slice(&alpha.to_ne_bytes());
            }

            let texture = Image::new(
                Extent3d {
                    width: info.width,
                    height: info.height,
                    depth_or_array_layers: 1,
                },
                TextureDimension::D2,
                rgba_data,
                format,
            );

            load_context.set_default_asset(LoadedAsset::new(texture));
            Ok(())
        })
    }

    fn extensions(&self) -> &[&str] {
        &["hdr"]
    }
}