[рони]

<style>
  canvas {
    border: 1px solid #000;
  }
</style>
<canvas id="myCanvas" width="400" height="400"></canvas>
<button id="resizeButton">resize button</button>

<script>
  var canvas = document.getElementById("myCanvas")
  var ctx = canvas.getContext("2d")

  function update() {
    ctx.fillStyle = "#FF0000"
    ctx.fillRect(0, 0, 150, 75)
  }

  document.getElementById('resizeButton').addEventListener('click', () => {
    var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    canvas.width = 600;
    ctx.putImageData(imageData, 0,  0);
  })

  update()
</script>