Yes, in direct sunlight the decking will be warm. Aluminium dissipates heat faster than any other material and tests have show Knotwood aluminium decking to slightly cooler than traditional wood, composites and ipe.
The process involves the physical reaction between special inks and a polyurethane or polyester powder coating. Under controlled conditions of heat and pressure, photographic images are absorbed directly into the powder coating.
See making Knotwood under resources / knotwood / making knotwood.