Liam Neeson -- Healthy As a Horse ... Despite Sickly Photo

Liam Neeson had fans worried when he was spotted over the weekend looking frail and gaunt ... but his rep says the "Taken" star is in good health.

The rep says the 63-year-old actor is "healthy as ever," despite his ghostly appearance in the pic. The rep adds Neeson changed his diet and started doing more exercise about a year ago and credits that for the weight loss.

Plus, the rep says ... it's just an unflattering pic.

Apparently one of Neeson's "particular skills" ... is not always taking a great photo.