1. A computer-executed method comprising: accessing an image comprising an unidentified key phrase in image format; processing a portion of the image associated with the unidentified key phrase using a character recognition algorithm to generate a list of candidate key phrases in text format; accessing, by a computer processor, a plurality of social media content items in text format authored by users of a social networking system, the social media content items each comprising at least one key phrase previously associated with the image and at least one of the candidate key phrases; determining, by the computer processor, for each candidate key phrase, a count of the number of the content items comprising that candidate key phrase and at least one of the key phrases previously associated with the image; selecting, by the computer processor, one of the candidate key phrases as being the unidentified key phrase based on the determined count of the content items in each set; and sending content associated with the image to one or more users of the social networking system based on the social media content items including the selected candidate key phrase.