1. A device for detecting a region of interest on a delivery object, comprising: a clustering engine; a mapping engine; the clustering engine comprising cluster identification data, an item of the cluster identification data representing a cluster of image data items in a training set of image data items; the mapping engine comprising a group of heat maps, a heat map being associated with a cluster represented by the cluster identification data, and providing for cells of a grid into which an image data item is tessellated in the training set of image data items a probability distribution for a probability of the cell belonging to a defined region of interest given the number of blobs in the cell; the clustering engine being configured to input an image data item of the delivery object and to use the cluster identification data to associate the input image data item with at least one cluster; the mapping engine being configured to use a heat map of the associated cluster to determine at least one region of interest in the image data item.