Abstract: An apparatus and method for processing image data to derive edges and line segments. Image intensity data is processed in one dimension along a series of scan lines to produce an intensity curve (10). Pairs of points along a scan line curve (10) representing curvature extrema (20) are checked to determine if the intensity difference between the curvature extrema (20) are characteristic of edges. Edge points are then determined between pairs of curvature extrema. Edge points found between curvature extrema (20) are then correlated with other edge points in previous scan lines to determine if they fall within a range of predicted line segments. Line segment data may then be processed at higher levels to identify objects in the data.