demo to show swift converting images to thumbnails in a directory , requires ImageMagick linux package
initial testing on a dual core (i7-3520m) laptop in the memory filesystem (/dev/shm ) and 42 photos showed some scaling :
swift-t -n 2 : 18s swift-t -n 3 : 13s swift-t -n 4 : 13s parsl: 12s