1. A feature detection apparatus comprising: an input unit for receiving at least two area indicator lines for defining in a digital image an area of interest comprising parts of an object; a parameter range defining unit for defining ranges of at least two parameters of a parametric shape to be introduced into the digital image, for which the parametric shape intersects at least one of the area indicator lines; a parameter selection unit for selecting a combination of parameter values from the parameter ranges, for which the parametric shape constitutes an approximation to an object feature of the object in the area of interest; and an output unit for providing the parametric shape based on said combination of parameter values for display in the digital image.