1. A system, comprising: one or more processors; and memory including instructions that, upon execution by the one or more processors, cause the system to: receive a first image of an item from a client device associated with a first user of the system; identify a second user of the system who is connected to the first user by a social network; constrain an image search corpus to a collection of images of items purchased by the second user from the system; identify the item by extracting one or more shapes or objects in the first image and matching, via content-based image retrieval, the one or more shapes or objects in the first image to one or more shapes or objects in a second image of the image search corpus; and present, to the client device, information of one or more items offered for purchase by the system that have images whose shapes or objects are similar to the one or more shapes or objects in the second image.