A first database search is performed for images similar to a first query image, and a first plurality of images that result from the first database search are provided. The first plurality of images are selectable to provide a second query image. A second database search is performed for images similar to the second query image, and a second plurality of images that result from the second search are provided. The second plurality of images are selectable to provide a third query image. A third database search is performed for images similar to the third query image; and a third plurality of images that result from the third database search are provided. The third plurality of images are selectable for providing a fourth query image. The search can continue to additional depths. Similarity may be determined by pixel color gradients using windows of computation.