libVPX convert VPX_IMG_FMT_I420 -> RGB

How I can convert VPX_IMG_FMT_I420 vpx_image_t to RGB?

Example code:

int DecodeFrame()
{
  vpx_video_reader_read_frame(reader);
  vpx_codec_iter_t iter = NULL;
  vpx_image_t *img = NULL;
  size_t frame_size = 0;
  const unsigned char *frame = vpx_video_reader_get_frame(reader, &frame_size);
  if (vpx_codec_decode(&codec, frame, (unsigned int)frame_size, NULL, 0)) return 0;

  img = vpx_codec_get_frame(&codec, &iter);

// here I need to convert img to RGB array

  return 1;
};