Apparatus and method for modification of emotion conveyed by an image. In one aspect, a metric corresponding to the emotion conveyed by an image is generated, and a command for modifying the emotion of the image causes the emotion conveyed by the image to be changed according to the specified change to emotion. The command to modify the image emotion can be made via an emotion keyword, and can include an indicated magnitude of emotion change. Emotion conveyed by an image can be specified via an emotion vector, where elements of the vector correspond with emotions arranged along orthogonal dimensions in an emotion space. In one aspect, an emotion predictor is trained to predict the emotion conveyed by an image via determining characteristic values for a set of image feature categories, based on a set of images associated with emotion keywords of the emotion space.