Grayscale textures (LumaU8) showing up in red

[jzimmerman135]

I am trying to render a calibration background, but the black and white marker textures are being drawn in red instead of white for some reason.

I don't think it's a problem with wgpu because I got it to work in bevy earlier.

This is a minimum reproducible version. I'm on MacOS with Arm64 M1.
These images were created with the opencv api.

use std::path::PathBuf;

use nannou::prelude::*;

struct Model {
    marker: wgpu::Texture,
}

pub fn main() {
    nannou::app(model).run();
}

fn model(app: &App) -> Model {
    app.new_window().fullscreen().view(view).build().unwrap();
    let marker =
        wgpu::Texture::from_path(app, PathBuf::from("assets/markers/marker0.png")).unwrap();
    Model { marker }
}

fn view(app: &App, model: &Model, frame: Frame) {
    frame.clear(WHITE);
    let draw = app.draw();
    draw.texture(&model.marker).x_y(0., 0.).w_h(100., 100.);
    draw.to_frame(app, &frame).unwrap();
}

[jzimmerman135]

Here is a screenshot of the app running

[jzimmerman135]

It seems to be related to images producted from numpy arrays with python's PIL library

[jzimmerman135]

This could be fixed by either rendering with a special shader for grayscale images, or since many other common formats like rgb8, bgr8 and rgb16 all have a clone and convert step, "unsupported" image types like Luma could be converted as well.

A PR would involved changing

// line 511 nannou_wgpu/src/texture/image.rs 
pub fn load_texture_from_image(
    device: &wgpu::Device,
    queue: &wgpu::Queue,
    usage: wgpu::TextureUsages,
    image: &image::DynamicImage,
) -> wgpu::Texture {
    use image::DynamicImage::*;
    match image {
        ImageLuma8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageLumaA8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageRgba8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageBgra8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageLuma16(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageLumaA16(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageRgba16(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageRgb8(_img) => {
            let img = image.to_rgba8();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
        ImageBgr8(_img) => {
            let img = image.to_bgra8();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
        ImageRgb16(_img) => {
            let img = image.to_rgba16();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
    }
}

pub fn load_texture_from_image(
    device: &wgpu::Device,
    queue: &wgpu::Queue,
    usage: wgpu::TextureUsages,
    image: &image::DynamicImage,
) -> wgpu::Texture {
    use image::DynamicImage::*;
    match image {
        ImageRgba8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageBgra8(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageRgba16(img) => load_texture_from_image_buffer(device, queue, usage, img),
        ImageRgb8(_img) => {
            let img = image.to_rgba8();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
        ImageBgr8(_img) => {
            let img = image.to_bgra8();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
        ImageRgb16(_img) => {
            let img = image.to_rgba16();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
        _ => {
            let img = image.to_rgba8();
            load_texture_from_image_buffer(device, queue, usage, &img)
        }
    }
}