An image processing apparatus uses first and second digital vascular image data to register two images. The two images may be from different imaging modes. The first and second images are processed with a two-dimensional, directional filter (500) that has the effect of producing clusters of orthogonally adjacent image data points in which the magnitude of an intensity gradient between each orthogonally adjacent image data point is less than a predetermined value. Subsequently, common clusters are identified between the first and second image data using a corner detecting algorithm (600). The directional filter produces “stepping” features, where vascular features would otherwise appear with smooth edges. These numerous features are identified by the corner detecting algorithm and can be used (1000) for registering common clusters between the first and second image data. The filter may be a rotating Gabor filter matched to vascular features in the images.
