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

use super::{Texture, TextureFormat};
use anyhow::Result;
use bevy_asset::AssetLoader;
use bevy_math::Vec2;
use std::path::Path;

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

impl AssetLoader<Texture> for HdrTextureLoader {
    fn from_bytes(&self, _asset_path: &Path, bytes: Vec<u8>) -> Result<Texture> {
        let format = TextureFormat::Rgba32Float;
        debug_assert_eq!(
            format.pixel_size(),
            4 * 4 * 1,
            "Format should have 32bit x 4 size"
        );

        let decoder = image::hdr::HdrDecoder::new(bytes.as_slice())?;
        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());
        }

        Ok(Texture::new(
            Vec2::new(info.width as f32, info.height as f32),
            rgba_data,
            format,
        ))
    }

    fn extensions(&self) -> &[&str] {
        static EXTENSIONS: &[&str] = &["hdr"];
        EXTENSIONS
    }
}