Understanding Zoom Using Canvas' setTransform

I am currently using JavaScript to create drawing software.
So I want to create a zoom function, but it doesn't work.
Below is the code

 function zoom(x,y)
{
    varcanvas= document.getElementById('canvas');
    varctx = canvas.getContext('2d');
    var width = canvas.width;
    var height = canvas.height;

    var ImageData=ctx.getImageData(0,0, width, height);

    ctx.setTransform(x,0,0,y,0,0);

    ctx.putImageData(ImageData,0,0);
}

I changed the zoom function x and y arbitrarily, but it doesn't work.
After changing the magnification, I pasted the image using drawImage and found the magnification specified.
Can't I use getImageData or putImageData?
There are many ways to change the magnification, but I would like to use setTransform for future production.

Why can't I do it well?

If you understand, please give us some advice or suggestions.