How to define an adaptive grid or coordinate system on an image?

I often need to draw on an image precisely.
For this, I draw two paths on the image and I position the points proportionally on the image.
This solution allows me to change the size of the image without needing to recalculate the points like in the image below.

documentclass[A4]{article}

usepackage{tikz}

usepackage{graphicx}
usetikzlibrary{calc}

begin{document}

begin{tikzpicture}
node(img){includegraphics[width=0.5textwidth]{tux.png}};
draw[red] (img.west) -- (img.east)
coordinate[pos=0.53](ax)
coordinate[pos=0.41](bx);

draw[red] (img.south) -- (img.north)
coordinate[pos=0.74] (ay)
coordinate[pos=0.74] (by);

draw[red,ultra thick] (ax|-ay) circle (0.2cm);

draw[blue,ultra thick] (bx|-by) circle (0.2cm);
end{tikzpicture}
begin{tikzpicture}
node(img){includegraphics[width=0.3textwidth]{tux.png}};
path[red] (img.west) -- (img.east)
coordinate[pos=0.53](ax)
coordinate[pos=0.41](bx);

path[red] (img.south) -- (img.north)
coordinate[pos=0.74] (ay)
coordinate[pos=0.74] (by);

draw[red,ultra thick] (ax|-ay) circle (0.2cm);

draw[blue,ultra thick] (bx|-by) circle (0.2cm);
end{tikzpicture}
begin{tikzpicture}[rotate=30,transform shape]
node(img){includegraphics[width=0.5textwidth]{tux.png}};
draw[red] (img.west) -- (img.east)
coordinate[pos=0.53](ax)
coordinate[pos=0.41](bx);

draw[red] (img.south) -- (img.north)
coordinate[pos=0.74] (ay)
coordinate[pos=0.74] (by);

draw[red,ultra thick] (ax|-ay) circle (0.2cm);

draw[blue,ultra thick] (bx|-by) circle (0.2cm);
end{tikzpicture}
end{document}

what I would like is an command or an environment

begin {imageScope}[xstep = imageWidth / 10, ystep = imageHeight / 10]
...
...
end{imageScope}

which will allow me to position the different points in a relative way directly on the image with a drawing command in the scope like

draw (x1, y1) - (x2, y2);

where (x1, y1) and (x2, y2) are defined in the coordinate system associated with the image.

documentclass[tikz,border=3.14mm]{standalone}

newcommand{imgrid}[1]
    {
    path (#1.south west);
    pgfgetlastxy{xmin}{ymin};
    path (#1.north east);
    pgfgetlastxy{xmax}{ymax};
    pgfmathsetmacro{xstp}{(xmax-xmin)/10}
    pgfmathsetmacro{ystp}{(ymax-ymin)/10}
    draw[gray] (xmin,ymin) grid[xstep=xstp pt,ystep=ystp pt] (xmax,ymax);
    }

begin{document}

    begin{tikzpicture}
        node (img) {includegraphics[scale=0.5]{pingoo.jpg}};
        imgrid{img};
    end{tikzpicture}
    
end{document}