use eframe::{egui, epi};

#[derive(Default)]
struct MyApp {
    texture: Option<egui::TextureId>,
}

impl epi::App for MyApp {
    fn name(&self) -> &str {
        "Show an image with eframe/egui"
    }

    fn update(&mut self, ctx: &egui::CtxRef, frame: &mut epi::Frame<'_>) {
        if self.texture.is_none() {
            // Load the image:
            let image_data = include_bytes!("rust-logo-512x512.png");
            use image::GenericImageView;
            let image = image::load_from_memory(image_data).expect("Failed to load image");
            let image_buffer = image.to_rgba8();
            let size = (image.width() as usize, image.height() as usize);
            let pixels = image_buffer.into_vec();
            assert_eq!(size.0 * size.1 * 4, pixels.len());
            let pixels: Vec<_> = pixels
                .chunks_exact(4)
                .map(|p| egui::Color32::from_rgba_unmultiplied(p[0], p[1], p[2], p[3]))
                .collect();

            // Allocate a texture:
            let texture = frame
                .tex_allocator()
                .alloc_srgba_premultiplied(size, &pixels);
            self.texture = Some(texture);
        }

        egui::CentralPanel::default().show(ctx, |ui| {
            ui.heading("Here is an image for you:");
            if let Some(texture) = self.texture {
                ui.image(texture, egui::Vec2::splat(256.0));
            }
        });
    }
}

fn main() {
    let options = eframe::NativeOptions::default();
    eframe::run_native(Box::new(MyApp::default()), options);
}