Draw stroke behind an outline transparent image using canvas?

Question

I need to draw stroke using mousemove behind or under a transparent png image on a canvas tag.

#canvas{
background:../images/wat.png ;}

Using css is not useful because stroke will affect background image. The .png image must be intact. I`ve also tried the following function:

function make_base()
{
  base_image = new Image();

  base_image.src = '../images/wat.png';

  base_image.onload = function(){

    ctx.drawImage(base_image, 0, 0,window.innerWidth, window.innerHeight);

  }

Answer 1

使用CSS解决：

pointer-event: none;