Using a food processor, blend together the black beans and garbanzo beans; transfer to a large bowl. Add remaining ingredients; blend well. Shape into patties. Saute in a small amount of olive oil over medium-high heat, 2-3 minutes per side until browned. Reduce heat; continue to cook until heated through. Serve in pitas or wrapped in a tortilla half; top with fresh diced tomatoes and purple onion. Makes 4 servings.