function expectedImageSize(displayedWidth, displayedHeight, DPR) {
  const width = Math.ceil(quantizeDpr(DPR) * displayedWidth);
  const height = Math.ceil(quantizeDpr(DPR) * displayedHeight);
  return [width, height];
}
Compute the size an image should have given the display dimensions and pixel density.

@param {number} displayedWidth
@param {number} displayedHeight
@param {number} DPR
@return {[number, number]}