imageSource = http://abc/myimage.jpg
extractedFaces = array of face objects, each object looks like {boundingBox: [], ...}
originalSize = original size of image, looks like {height: 640px, width: 480px} only height is needed here

renderExtractedFaces = (imageSource, extractedFaces, originalSize) => {
    let results = []
    extractedFaces.forEach((face, i) => {
      let x = face.boundingBox[0]
      let y = face.boundingBox[1]
      let w = face.boundingBox[2] - x
      let h = face.boundingBox[3] - y

      let newX = x/h*100
      let newY = y/h*100
      let newW = w/h*100
      let newH = h/h*100

      results.push(
        <div key={`face-${i}`}>
          <div
            style={{
              backgroundImage: `url("${imageSource}")`,
              backgroundSize: `auto ${originalSize.height/h*100}px`,
              backgroundPositionX: `-${newX}px`,
              backgroundPositionY: `-${newY}px`,
              width: `${newW}px`,
              height: `${newH}px`
            }}
          />
        </div>
      )
    })

    return results
  }