code: function relativeRescale (enabledElement, oldCanvasWidth, oldCanvasHeight) {
    const scale = enabledElement.viewport.scale;
    const canvasWidth = enabledElement.canvas.width;
    const canvasHeight = enabledElement.canvas.height;
    const relWidthChange = canvasWidth / oldCanvasWidth;
    const relHeightChange = canvasHeight / oldCanvasHeight;
    const relChange = Math.sqrt(relWidthChange * relHeightChange);
  
    enabledElement.viewport.scale = relChange * scale;
  }
docs: Rescale the image relative to the changed size of the canvas
  
  @param {EnabledElement} enabledElement The Cornerstone Enabled Element
  @param {number} oldCanvasWidth The width of the canvas before the resize
  @param {number} oldCanvasHeight The height of the canvas before the resize
  @return {void}