SVG Filters and canvas pixels

Question

I am trying to retrieve the pixels of a canvas on which filters have been applied.

On this example below, I apply a filter on mycanvas1, draw an image on it and then draw that canvas on another canvas mycanvas2:

async function loadImageFromBase64(base64) {
  return new Promise(resolve => {
    const image = new Image();
    image.onload = () => resolve(image);
    image.src = base64;
  });
}

async function main() {
  const image = await(loadImageFromBase64(imageBase64));
  const mycanvas1 = document.getElementById('mycanvas1');
  const myctx1 = mycanvas1.getContext('2d');
  const mycanvas2 = document.getElementById('mycanvas2');
  const myctx2 = mycanvas2.getContext('2d');
  
  myctx1.drawImage(image, 0, 0);
  myctx2.drawImage(mycanvas1, 0, 0);
}

window.onload = main;

const imageBase64 = 'data:image/svg+xml;base64,<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Generator: Adobe Illustrator 15.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
	 width="128px" height="128px" viewBox="0 0 128 128" style="enable-background:new 0 0 128 128;" xml:space="preserve">
<g>
	<circle style="fill:#88C5CC;" cx="64" cy="64" r="64"/>
	<path style="fill:#80B9BF;" d="M110.723,107.716c-0.029-0.213-0.09-0.416-0.185-0.602c0.002-0.039,0.013-0.075,0.013-0.114
		c0-0.466-0.168-0.891-0.438-1.23c-0.045-0.375-0.19-0.718-0.414-1c-0.045-0.375-0.19-0.718-0.414-1
		c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1
		c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.188-0.717-0.413-1c-0.044-0.375-0.188-0.718-0.414-1
		c-0.043-0.375-0.188-0.718-0.413-1c-0.043-0.375-0.189-0.718-0.414-1c-0.043-0.375-0.189-0.718-0.414-1
		c-0.043-0.375-0.189-0.718-0.414-1c-0.043-0.375-0.189-0.718-0.414-1c-0.043-0.375-0.189-0.718-0.414-1
		c-0.043-0.375-0.188-0.717-0.412-1c-0.045-0.375-0.189-0.718-0.414-1c-0.027-0.234-0.094-0.455-0.195-0.658
		c0.004-0.037,0.012-0.073,0.012-0.111c0-0.466-0.168-0.891-0.438-1.23c-0.044-0.375-0.189-0.718-0.414-1
		c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1
		c-0.044-0.375-0.189-0.717-0.412-1c-0.045-0.375-0.189-0.718-0.414-1c-0.045-0.375-0.189-0.718-0.414-1
		c-0.045-0.375-0.189-0.718-0.414-1c-0.045-0.375-0.189-0.718-0.414-1c-0.045-0.375-0.189-0.718-0.414-1
		c-0.045-0.375-0.189-0.718-0.414-1c-0.045-0.375-0.188-0.717-0.412-1c-0.045-0.375-0.19-0.718-0.414-1
		c-0.045-0.375-0.19-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1c-0.044-0.375-0.189-0.718-0.414-1
		c-0.044-0.375-0.189-0.718-0.414-1c-0.025-0.234-0.093-0.455-0.193-0.658c0.002-0.037,0.012-0.073,0.012-0.111
		c0-0.466-0.168-0.891-0.438-1.23c-0.044-0.375-0.188-0.717-0.413-1c-0.044-0.375-0.189-0.718-0.414-1
		c-0.043-0.375-0.189-0.718-0.414-1c-0.043-0.375-0.188-0.718-0.414-1c-0.043-0.375-0.188-0.718-0.414-1
		c-0.043-0.375-0.188-0.717-0.414-1c-0.043-0.375-0.188-0.717-0.414-1c-0.043-0.375-0.188-0.717-0.412-1
		c-0.045-0.375-0.189-0.716-0.413-0.999c-0.044-0.376-0.189-0.718-0.414-1.001c-0.044-0.375-0.188-0.717-0.414-1
		c-0.044-0.375-0.188-0.717-0.414-1c-0.044-0.375-0.188-0.717-0.414-1c-0.044-0.375-0.188-0.717-0.414-1
		c-0.044-0.375-0.188-0.717-0.414-1c-0.044-0.375-0.188-0.717-0.414-1c-0.026-0.233-0.093-0.453-0.192-0.655
		c0.002-0.039,0.012-0.075,0.012-0.114c0-0.466-0.168-0.89-0.438-1.231c-0.045-0.375-0.19-0.717-0.414-1
		c-0.045-0.375-0.19-0.717-0.414-1c-0.045-0.375-0.19-0.717-0.414-1c-0.045-0.375-0.19-0.717-0.414-1
		c-0.045-0.375-0.19-0.717-0.414-1c-0.045-0.375-0.19-0.717-0.414-1c-0.045-0.375-0.189-0.716-0.413-0.999
		c-0.044-0.376-0.19-0.718-0.414-1.001c-0.044-0.375-0.19-0.717-0.414-1c-0.044-0.375-0.19-0.717-0.414-1
		c-0.044-0.375-0.19-0.717-0.414-1c-0.044-0.375-0.19-0.717-0.414-1c-0.044-0.375-0.19-0.717-0.414-1
		c-0.044-0.375-0.188-0.716-0.413-0.999c-0.043-0.376-0.189-0.718-0.414-1.001c-0.043-0.375-0.188-0.717-0.414-1
		c-0.043-0.375-0.188-0.717-0.414-1C80.818,32.778,79.98,32,78.96,32h-30c-1.1,0-2,0.9-2,2c0,0.32,0.083,0.619,0.219,0.888
		c-0.002,0.038-0.012,0.074-0.012,0.112c0,0.466,0.168,0.89,0.438,1.231c0.045,0.375,0.19,0.717,0.414,1
		c0.045,0.375,0.189,0.716,0.414,0.999c0.043,0.376,0.189,0.718,0.413,1.001c0.044,0.375,0.19,0.717,0.414,1
		c0.044,0.375,0.19,0.717,0.414,1c0.044,0.375,0.19,0.717,0.414,1c0.044,0.375,0.19,0.717,0.414,1c0.044,0.375,0.19,0.717,0.414,1
		c0.011,0.087,0.022,0.172,0.044,0.256V107v0.512v0.512c0,2.168,0.537,4.205,1.475,6.002c0.246,0.896,0.58,1.752,1,2.561
		c0.246,0.896,0.58,1.754,1,2.563c0.246,0.896,0.58,1.752,1,2.561c0.317,1.156,0.789,2.245,1.394,3.248
		c0.171,0.467,0.371,0.923,0.599,1.361c0.131,0.474,0.287,0.935,0.467,1.384c2.011,0.19,4.045,0.297,6.105,0.297
		C82.438,128,99.043,120.191,110.723,107.716z"/>
	<path style="fill:#F5F5F5;" d="M50.953,36v71c0,7.18,5.82,13,13,13c7.18,0,13-5.82,13-13V36H50.953z"/>
	<path style="fill:#96E652;" d="M72.953,87v20c0,4.962-4.037,9-9,9s-9-4.038-9-9V87H72.953z"/>
	<path style="fill:#B3B3B3;" d="M62.953,46h-7c-0.553,0-1-0.448-1-1s0.447-1,1-1h7c0.553,0,1,0.448,1,1S63.506,46,62.953,46z"/>
	<path style="fill:#B3B3B3;" d="M57.953,50h-2c-0.553,0-1-0.448-1-1s0.447-1,1-1h2c0.553,0,1,0.448,1,1S58.506,50,57.953,50z"/>
	<path style="fill:#B3B3B3;" d="M62.953,54h-7c-0.553,0-1-0.448-1-1s0.447-1,1-1h7c0.553,0,1,0.448,1,1S63.506,54,62.953,54z"/>
	<path style="fill:#B3B3B3;" d="M57.953,58h-2c-0.553,0-1-0.448-1-1s0.447-1,1-1h2c0.553,0,1,0.448,1,1S58.506,58,57.953,58z"/>
	<path style="fill:#B3B3B3;" d="M62.953,62h-7c-0.553,0-1-0.448-1-1s0.447-1,1-1h7c0.553,0,1,0.448,1,1S63.506,62,62.953,62z"/>
	<path style="fill:#B3B3B3;" d="M57.953,66h-2c-0.553,0-1-0.448-1-1s0.447-1,1-1h2c0.553,0,1,0.448,1,1S58.506,66,57.953,66z"/>
	<path style="fill:#B3B3B3;" d="M62.953,70h-7c-0.553,0-1-0.448-1-1s0.447-1,1-1h7c0.553,0,1,0.448,1,1S63.506,70,62.953,70z"/>
	<path style="fill:#B3B3B3;" d="M57.953,74h-2c-0.553,0-1-0.448-1-1s0.447-1,1-1h2c0.553,0,1,0.448,1,1S58.506,74,57.953,74z"/>
	<path style="fill:#B3B3B3;" d="M62.953,78h-7c-0.553,0-1-0.448-1-1s0.447-1,1-1h7c0.553,0,1,0.448,1,1S63.506,78,62.953,78z"/>
	<path style="fill:#B3B3B3;" d="M57.953,82h-2c-0.553,0-1-0.448-1-1s0.447-1,1-1h2c0.553,0,1,0.448,1,1S58.506,82,57.953,82z"/>
	<circle style="fill:#F5F5F5;" cx="71.953" cy="27" r="2"/>
	<circle style="fill:#F5F5F5;" cx="81.953" cy="11" r="2"/>
	<circle style="fill:#F5F5F5;" cx="81.953" cy="23" r="4"/>
	<circle style="fill:#F5F5F5;" cx="72.953" cy="15" r="3"/>
	<path style="fill:#F5F5F5;" d="M80.953,34c0,1.1-0.9,2-2,2h-30c-1.1,0-2-0.9-2-2l0,0c0-1.1,0.9-2,2-2h30
		C80.053,32,80.953,32.9,80.953,34L80.953,34z"/>
	<rect x="50.953" y="36" style="fill:#CCCCCC;" width="26" height="1"/>
</g>
</svg>
';

<!DOCTYPE html>
<html>
<head>
  <title>My Filter</title>
  <meta charset="utf-8">
  <style>
    #mycanvas1 {
      filter: url(#myfilter);
      border: 3px solid blue;
    }

    #mycanvas2 {
      border: 3px solid red;
    }
</style>
</head>
<body>
  <canvas id="mycanvas1"></canvas>
  <canvas id="mycanvas2"></canvas>

  <svg>
    <filter id="myfilter" x="0" y="0" width="100%" height="100%">
      <feColorMatrix type="luminanceToAlpha"/>
    </filter>
  </svg></body>
</html>

But the filter, it seems, are not applied on the canvas pixels. They are post-processed, that is why the second canvas contains the image without the filter. Is there any way to retrieve the pixels of the canvas with the filter applied?

I need this because I need to perform some operation ex-post of the filter in javascript.