9. A non-transitory computer readable storage medium comprising instructions that, when executed by at least one processor, cause a computer system to: determine a probability that a first unknown person instance in an image is each of a plurality of known person instances from images in an image gallery; identify a plurality of context cues between one or more of the first unknown person instance and one or more known person instances of the plurality of known person instances or between known person instances of the plurality of known person instances; determine a context weight for each combination of the first unknown person instance and each known person instance from the plurality of known person instances using a conditional random field algorithm based on the identified plurality of context cues; calculate a contextual probability based on the determined probabilities and the determined context weights; and identify the first unknown person instance as a known person instance from the plurality of known person instances with a highest contextual probability.
9. A non-transitory computer readable storage medium comprising instructions that, when executed by at least one processor, cause a computer system to: determine a probability that a first unknown person instance in an image is each of a plurality of known person instances from images in an image gallery; identify a plurality of context cues between one or more of the first unknown person instance and one or more known person instances of the plurality of known person instances or between known person instances of the plurality of known person instances; determine a context weight for each combination of the first unknown person instance and each known person instance from the plurality of known person instances using a conditional random field algorithm based on the identified plurality of context cues; calculate a contextual probability based on the determined probabilities and the determined context weights; and identify the first unknown person instance as a known person instance from the plurality of known person instances with a highest contextual probability. 13. The non-transitory computer readable storage medium as recited in claim 9 , wherein the instructions, when executed by the at least one processor, cause the computer system to calculate the contextual probability by summing the determined probabilities and the determined context weights.