Allowed options:
  --help                produce help message
  -I [ --images ] arg   * directory of the source images
  -n arg                limit the maximum number of source images
  -t [ --target ] arg   * target image
  --xn arg (=100)       number of x blocks
  --yn arg (=150)       number of y blocks
  --precision arg (=8)  histogram size
  --threads arg         number of threads for generating Photomosaic (0 for serial)
  -o [ --output ] arg   output path