A method for recognizing an occurrence of an object in an image is provided where the appearance of the object may vary from one occurrence to another. The method includes defining a model set for object recognition, the model set including at least one model, acquiring a target image, processing the target image according to a set of morphological operations to obtain a set of morphologically-processed target images, performing object recognition on the set of morphologically-processed target images for the defined model set, and selecting at least one candidate occurrence of a model of the defined model set in the target image based on the object recognition performed on the set of morphologically-processed target images.