How can I have the pixel coordinate X,Y after ArrayFire match_template?

I'm trying to use the matching_template function from the ArrayFire library But I don't know how to find the X and Y coordinates of the best matching value. I was using the imageproc library to perform this function and there it has the find_extremes function that returns the coordinates to me. How would you do the same using ArrayFire lib?

My example using imageproc

    let template = image::open("connect.png").unwrap().to_luma8();
    let screenshot = image::open("screenshot.png").unwrap().to_luma8();

   let matching_probability= imageproc::template_matching::match_template(&screenshot, &template, MatchTemplateMethod::CrossCorrelationNormalized);
   let positions = find_extremes(&matching_probability);

 println!("{:?}", positions);

Extremes { max_value: 0.9998113, min_value: 0.42247093, max_value_location: (843, 696), min_value_location: (657, 832) }

My example using ArrayFire

   let template: Array<u8> = arrayfire::load_image(String::from("connect.png"), true);
   let screenshot: Array<u8> = arrayfire::load_image(String::from("screenshot.png"), true);

   let template_gray = rgb2gray(&template, 0.2126, 0.7152, 0.0722);
   let screen_gray =  rgb2gray(&screenshot, 0.2126, 0.7152, 0.0722);
   let matching_probability = arrayfire::match_template(&screen_gray, &template_gray, arrayfire::MatchType::LSAD);

af_print!("{:?}", matching_probability);

139569.0469 140099.2500 139869.8594 140015.7969 140680.9844 141952.5781 142602.7344 142870.7188...

from here I don't havy any idea how to get the best matching pixel coordinates.

Solution

Arrayfire doesn't provide "extremum" function, but separate min and max families of functions.

The one that provides index informations are prefixed with i.

imin_all and imax_all returns the min and max value indexes respectively wrapped in a tupple.

You can derive pixel position from value indexes and array dimensions, knowing that arrayfire is column major.

let template: Array<u8> = arrayfire::load_image(String::from("connect.png"), true);
let screenshot: Array<u8> = arrayfire::load_image(String::from("screenshot.png"), true);

let template_gray = rgb2gray(&template, 0.2126, 0.7152, 0.0722);
let screen_gray = rgb2gray(&screenshot, 0.2126, 0.7152, 0.0722);
let matching_probability = arrayfire::match_template(&screen_gray, &template_gray, arrayfire::MatchType::LSAD);

let (min, _, min_idx) = imin_all(&matching_probability);
let (max, _, max_idx) = imax_all(&matching_probability);

let dims = matching_probability.dims();
let [_, height, _, _] = dims.get();

let px_x_min = min_idx as u64 / height;
let px_y_min = min_idx as u64 % height;

let px_x_max = max_idx as u64 / height;
let px_y_max = max_idx as u64 % height;

af_print!("{:?}", matching_probability);
println!("Minimum value: {} is at pixel ({},{}).",min, px_x_min, px_y_min);
println!("Maximum value: {} is at pixel ({},{}).", max, px_x_max, px_y_max);