Calculate pixel height in inches/mm at a given distance

gistfile1.txt

/**
 * @param {number} srcPixels Number of pixels used when rendering on a standard desktop dispaly. Defaults to 1 pixel
 * @param {number} distance Distance in inches at which the item is rendered. Defaults to 28 inches (distance specified in the CSS spec)
 * 
 * https://www.w3.org/TR/css-values-4/#reference-pixel
 */
function getProjectedPixel({pixels = 1, distance = 28} = {}) {
  const inToMm = (inch) => inch * 25.4;
  
  const opposite = distance;
  const srcPixels = pixels;
  
  const refAdjacent = 28; // inches from viewer
  const refOpposite = srcPixels/96; // height in inches of pixels
  const refAngle = Math.atan2(refOpposite, refAdjacent);// 180 / Math.PI;
  const result = {
    distance: {
      inches: distance,
      mm: inToMm(distance),
    },
    angle: {
      radians: refAngle,
      degress: refAngle * 180 / Math.PI,
    },
    height: {
      inches: Math.tan(refAngle) * opposite,
      mm: inToMm(Math.tan(refAngle) * opposite),
    },
  }
  return result;
}