Convert Mat to Vec<u8> (Rust OpenCV)

Question

I'm really new to Rust and fairly new to OpenCV (yea).

I have a simple OpenCV example working in a seperate POC. But then integrating it into a workflow pipeline I need to return a buffer in type Vec<u8> .

Img is a Mat object which has this to_vec_2d method. But I'm unsure how to cast it to u8?

I'm thinking I might have to iterate through the Mat type. Is it possible to map it u8?

fn edge_detect(width: u32, height: u32, bytes: Vec<u8>, _metadata: Metadata) -> (u32, u32, Vec<u8>) {
    let img = imdecode(&Vector::from_iter(bytes), imgcodecs::IMREAD_ANYCOLOR).expect("Failed to decode");
    let mut result = img.clone();
    canny(&img, &mut result, 100.0, 200.0, 3, false).expect("Failed to find edges");
    let vec_result : Vec<u8> = result.to_vec_2d().expect("Cannot convert to vector");
    (width, height, vec_result)
}

Answer 1

You can use flat_map on an iterator to get them:

fn main() {
    let vec_2d = vec![vec![0, 1], vec![2, 3]];
    let v: Vec<u8> = vec_2d.iter().flat_map(|v| v.iter()).cloned().collect();
    println!("{:?}", v);
}

Playground