Abstract: A raster-to-vector conversion process for converting a pattern descriptive coded image into a vector coded image. A progress marking plane with structural elements determined as a function of pattern data in the image is created in pattern descriptive format. The progress marking plane is pre-loaded with index data stored in the structural elements and indicative of an aspect similarity between image-forming units in the image. Object contours in the image are searched as a function of an aspect correlation between the image-forming units as determined from the index data. The faces of the image-forming units explored while searching are marked in associated ones of the structural elements of the progress marking plane, to prevent a face forming a part of an object contour found while searching from being considered again.