Apparatus for transforming a two-level image into contour vectors by decomposing composite figures into "unitary" (open) and closed-loop figures, especially suitable for minimizing memory use while maintaining system processing speed

Claim 1

An apparatus for transforming a two-level image into contour vectors and forming a center line, the apparatus comprising: a) dividing and correcting means including: 1) means for extracting a plurality of characteristic points at which an absolute value of a difference in angle between contour vectors is greater than a first threshold; 2) means for determining vectors which connect two of the plurality of characteristic points which are spaced apart a distance which is smaller than a predetermined line width; and 3) means for reconstructing the contour vectors based on the determined vectors, the reconstructing step constituting a step of decomposing a composite figure having (1) at least one unitary figure defined by a single contour loop and (2) at least one closed loop figure defined by two contour loops, into unitary and closed loop figures which are distinguishable from each other; and b) center line determining means including: 1) means for extracting, from among the contour vectors reconstructed by the dividing and correcting means, (1) a first contour vector and (2) a second contour vector closest to and opposite in direction from the first contour vector; and 2) means for sequentially determining, based on the first and second extracted contour vectors, the center line.

Claim 2

An apparatus for transforming a two-level image into contour vectors and forming a center line, the apparatus comprising: a) dividing and correcting means including: 1) means for extracting a plurality of characteristic points at which an absolute value of a difference in angle between contour vectors is greater than a first threshold; 2) means for determining vectors which connect two of the plurality of characteristic points which are spaced apart a distance which is smaller than a predetermined line width; and 3) means for reconstructing the contour vectors based on the determined vectors, the reconstructing step constituting a step of decomposing a composite figure having (1) at least one unitary figure defined by a single contour loop and (2) at least one closed loop figure defined by two contour loops, into unitary and closed loop figures which are distinguishable from each other; and b) center line determining means including: 1) means for extracting, from among the contour vectors reconstructed by the dividing and correcting means, (1) a first contour vector and (2) a second contour vector closest to and opposite in direction from the first contour vector; and 2) means for sequentially determining, based on the first and second extracted contour vectors, the center line.

Claim 6

An apparatus for transforming a line image of a two-level digital image into contour vectors by tracing a contour of said image in one direction, said apparatus comprising: contour tracing means for sequentially tracing black pixels of the line image, each adjoining white pixels, so as to produce contour vectors; first extracting means for extracting a point between said contour vectors as a characteristic point, when a difference in angle between the contour vectors has an absolute value greater than a threshold; first classifying means for classifying the points extracted by said first extracting means into (a) points at which the differences in angle are positive and (b) points at which the differences in angle are negative; connecting vector generating means for generating, in both a positive direction and a negative direction, a connecting vector, the connecting vector connecting, among the points where the differences in angle are positive, two points spaced apart a shortest distance smaller than a predetermined line width; second classifying means for reconstructing the contour vectors based on of the generated connecting vectors, and for distinguishing a unitary figure defined by an outer contour loop and a closed loop figure defined by an outer and an inner contour loop; second extracting means for extracting, from among the contour vectors defining the unitary figure or the closed loop figure, (a) a vector longer than a threshold and (b) a vector closest to and opposite in direction from said vector; and center line determining means for determining, based on the two extracted contour vectors, a center line and for sequentially determining center lines of additional vectors by using said two extracted contour vectors as a start point.

Claim 7

An apparatus for transforming a line image of a two-level digital image into contour vectors by tracing a contour of said image in one direction, said apparatus comprising: contour tracing means for sequentially tracing black pixels of the line image, each adjoining white pixels, so as to produce contour vectors; first extracting means for extracting a point between said contour vectors as a characteristic point, when a difference in angle between the contour vectors has an absolute value greater than a threshold; first classifying means for classifying the points extracted by said first extracting means into (a) points at which the differences in angle are positive and (b) points at which the differences in angle are negative; connecting vector generating means for generating, in both a positive direction and a negative direction, a connecting vector, the connecting vector connecting, among the points where the differences in angle are positive, two points spaced apart a shortest distance smaller than a predetermined line width; second classifying means for reconstructing the contour vectors based on of the generated connecting vectors, and for distinguishing a unitary figure defined by an outer contour loop and a closed loop figure defined by an outer and an inner contour loop; second extracting means for extracting, from among the contour vectors defining the unitary figure or the closed loop figure, (a) a vector longer than a threshold and (b) a vector closest to and opposite in direction from said vector; and center line determining means for determining, based on the two extracted contour vectors, a center line and for sequentially determining center lines of additional vectors by using said two extracted contour vectors as a start point.