The numerous contacts that Greeks, Romans and other Europeans had with people of African origin have been portrayed in art for thousands of years. The objective of “The Image of the Black in Western Art,” says Henry Louis Gates Jr., chairman of the W.E.B. Du Bois Institute at Harvard University and editor-in-chief of The Root, is to capture and catalog that interaction for all of us to enjoy. Four of 10 projected volumes . . . are now available.