issue with call create_trackbar fun

[adminSxs]

code

use opencv::core::mul_f64_mat;
use opencv::highgui::{create_trackbar, imshow, named_window, wait_key, WINDOW_AUTOSIZE};
use opencv::imgcodecs::{imread, IMREAD_COLOR};
fn main()->opencv::Result<()>{
    let img=imread("avatar.png",IMREAD_COLOR)?;
    named_window("window",WINDOW_AUTOSIZE)?;
    create_trackbar("track","window",None,100,Some(Box::new(onchange)))?;

    imshow("window",&img)?;
    wait_key(0)?;
    Ok(())
}
fn onchange(value : i32){
    let a= value as f64/100.;
    println!("val={a}");
    // mul_f64_mat(a,&img);
}

I want to in onchange method use img variable, how should to do

[twistedfall]

The bindings don't expose the userdata argument as it's used for internal purposes. To capture the variables in your callback you should use Rust closures. You can check an example of this in the hough_lines example.

[adminSxs]

The bindings don't expose the userdata argument as it's used for internal purposes. To capture the variables in your callback you should use Rust closures. You can check an example of this in the hough_lines example.

thanks