Rotation matrix - https://jsfiddle.net/pq62hx0t/4/

a.js

function matrixArrayToCssMatrix(array) {
  return "matrix3d(" + array.join(',') + ")";
}

function multiplyMatrixAndPoint(matrix, point) {

  //Give a simple variable name to each part of the matrix, a column and row number
  var c0r0 = matrix[0],
    c1r0 = matrix[1],
    c2r0 = matrix[2],
    c3r0 = matrix[3];
  var c0r1 = matrix[4],
    c1r1 = matrix[5],
    c2r1 = matrix[6],
    c3r1 = matrix[7];
  var c0r2 = matrix[8],
    c1r2 = matrix[9],
    c2r2 = matrix[10],
    c3r2 = matrix[11];
  var c0r3 = matrix[12],
    c1r3 = matrix[13],
    c2r3 = matrix[14],
    c3r3 = matrix[15];

  //Now set some simple names for the point
  var x = point[0];
  var y = point[1];
  var z = point[2];
  var w = point[3];

  //Multiply the point against each part of the 1st column, then add together
  var resultX = (x * c0r0) + (y * c0r1) + (z * c0r2) + (w * c0r3);

  //Multiply the point against each part of the 2nd column, then add together
  var resultY = (x * c1r0) + (y * c1r1) + (z * c1r2) + (w * c1r3);

  //Multiply the point against each part of the 3rd column, then add together
  var resultZ = (x * c2r0) + (y * c2r1) + (z * c2r2) + (w * c2r3);

  //Multiply the point against each part of the 4th column, then add together
  var resultW = (x * c3r0) + (y * c3r1) + (z * c3r2) + (w * c3r3);

  return [resultX, resultY, resultZ, resultW];
}

// 將 float 轉成 number 避免出現 -1.23-e 這種值
const to = n => Number(n.toFixed(2))

var sin = Math.sin;
var cos = Math.cos;

// cx/y = current x, y 以左上角為準
function rotate(rotation, w, h, cx, cy) {
  // degree to radian
  var a = rotation * (Math.PI / 180)

	//
	var rotateZMatrix = [
	  cos(a), -sin(a),    0,    0,
	  sin(a),  cos(a),    0,    0,
	       0,       0,    1,    0,
	       0,       0,    0,    1
	];
	
  // 不管中心點位置，一律反推出左上角座標
  const diffX = w / 2
  const diffY = h / 2
  const x = -diffX
  const y = -diffY

  // 方型左上角距 (0, 0) 的距離，通常直接讀取方型的 (x, y) 就夠
  const offsetX = cx
  const offsetY = cy

  // 然後與 rotation matrix 相乘得到旋轉後位置
  const [x1, y1] = multiplyMatrixAndPoint(rotateZMatrix, [x, y, 0, 1])
	
  // 原點不在 (0,0) 時要加上離原點的位移值
  const finalX = to(x1 + diffX + offsetX)
  const finalY = to(y1 + diffY + offsetY)

  console.log('\n\n', { finalX, finalY }, '\t', { x, y, diffX, diffY, w, h })
}

// 測試
console.log(rotate(45, 100, 100, 0, 0))