Device for coding still images

• US 5,524,064 A
• Filed: 02/13/1995
• Issued: 06/04/1996
• Est. Priority Date: 09/09/1992
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Oddou, Christophe, Sirat, Jacques
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Kelley, Christopher S.
• Application Number:
  US08/388,118
• Time in Patent Office: 477 Days
• Field of Search: 382/180, 382/197, 382/204, 382/292
• US Class Current: 382/180
• CPC Class Codes: G06T 9/20 Contour coding, e.g. using detection of edges
• CPC Class Codes: H04N 19/20 using video object coding

Abstract

A device for coding still images has a device for segmenting the images into homogeneous regions whereto a specific label is attached, and a device for coding the contents of the contour. The contour coding device has a sub-assembly which detects contours for each regions, for each region successively considered, it detects points which are to form a series of control points and transforming the part of the contour joining two successive control points into a straight segment. Then the validity criterion is verified. If the criterion is not met, at least one supplementary control point is introduced between the two control points and so on until it is. The transformation is applied until the contour loop is completely closed.

Claims

1. A device for coding still images, comprising means for segmenting said images into homogeneous regions whereto a specific label is attached and detecting contours in the image to be coded, and contour coding means for coding the contents and the respective contour of at least one of said regions,

said contour coding means comprising a sub-assembly for coding contour information which itself comprises means for detecting, on the contour of each region successively considered, triplet points which are situated at the area of contact of at least three regions and which serve to form a series of original control points of the regions considered,

characterized in that said means for detecting control points comprises, for each contour of the detected region,

a circuit for tracking this contour,

a memory for storing coordinates of image points successively encountered on this contour,

a circuit for detecting said triplet points by comparison of the labels around each point of the stored contour of the current region, and

a memory for storing said triplet points which is also connected to the output of the memory for storing the coordinates of the contour of the current region being considered;

and

said sub-assembly for coding contour information also comprises;

a) means for transforming the contour fragment joining two successive said points in the direction in which the contour is followed into a straight segment;

b) means for testing said straight segment for conformance with at least one topological validity criterion which keeps the number of regions unchanged, said topological validity criterion being exclusive of determination of a distance of a point on said contour fragment from said straight segment;

c) means for introducing at least one supplementary control point into said series between said two successive control points when said validity criterion is not verified, for transforming a contour fragment terminating at the supplementary control point, testing each resulting straight fragments for conformance with said topological validity criterion, and repeating the introducing, transforming and testing until said validity criterion is verified, and then applying the transformation to each pair of successive control points until the contour loop is completely closed again; and

d) means for coding the polygonal contour formed by the succession of segments thus obtained.

12. A device as claimed in claim 1, further comprising means for repeating the detecting, transforming, testing and introducing in a similar manner for all regions of each image.

13. A device as claimed in claim 1, further comprising means for controlling re-initialization of the transformation procedure, including the same testing for said at least one topological validity criterion, for each set of two successive straight segments which are bounded by original control points.

2. A device for coding still images, comprising means for segmenting said images into homogeneous regions whereto a specific label is attached, and means for coding the contents and the respective contour of at least one of said regions, characterized in that said contour coding means comprise a sub-assembly for coding contour information which itself comprises:

a) means for detecting contours in the image to be coded;

b) means for detecting, on the contour of each region successively considered, points which serve to form a series of original control points of the region considered;

c) means for transforming the contour fragment joining two successive said points in the direction in which the contour is followed into a straight segment;

d) means for testing said straight segment for conformance with topological validity criteria which include;

said straight segment does not intersect the contour being considered at points outside said contour fragment,

said straight segment does not intersect another region not adjoining the current region being considered,

substitution of said straight segment does not eliminate a different region included in said current region, and

said straight segment is not tangent to yet another region thereby constricting yet a different region so as to cut said yet a different region into two distinct regions, and

said topological validity criteria being exclusive of determination of a distance of a point on said contour fragment from said straight segment;

e) means for introducing at least one supplementary control point into said series between said two successive control points when said validity criterion is not verified, for transforming a contour fragment terminating at the supplementary control point, testing each resulting straight fragments for conformance with said topological validity criterion, and repeating the introducing, transforming and testing until said validity criterion is verified, and then applying the transformation to each pair of successive control points until the contour loop is completely closed again; and

f) means for coding the polygonal contour formed by the succession of segments thus obtained.

9. A device as claimed in claim 2, further comprising means for repeating the detecting, transforming, testing and introducing in a similar manner for all regions of each image.

10. A device as claimed in claim 9, characterized in that said means for detecting control points comprises, for each contour of the detected region,

a circuit for tracking this contour,

a memory for storing coordinates of image points successively encountered on this contour,

a circuit for detecting on this contour triplet points which are situated at the area of contact of at least three regions, said triplet points forming said original control points, and

a memory for storing said triplet points which is also connected to the output of the memory for storing the coordinates of the contour of the current region being considered.

11. A device as claimed in claim 10, further comprising means for controlling re-initialization of the transformation procedure, including the same testing for at least one topological validity criterion, for each set of two successive straight segments which are bounded by original control points.

14. A device as claimed in claim 2, further comprising means for controlling re-initialization of the transformation procedure, including the same testing for at least one topological validity criterion, for each set of two successive straight segments which are bounded by original control points.

3. A device for coding still images, comprising means for segmenting said images into homogeneous regions whereto a specific label is attached, and means for coding the contents and the respective contour of at least one of said regions, characterized in that said contour coding means comprise a sub-assembly for coding contour information which itself comprises:

a) means for detecting contours in the image to be coded;

b) means for detecting, on the contour of each region successively considered, points which serve to form a series of original control points of the region considered;

c) means for transforming the contour fragment joining two successive said points in the direction in which the contour is followed into a straight segment, said means for transforming comprising two label memories for storing labels before and after transformation, respectively, and a circuit for determining labels corresponding to the regions adjoining the current region whose output signal is applied to said label memories;

d) means for testing said straight segment for conformance with at least one topological validity criterion, comprising a comparison circuit for inhibiting transformation in a given number of predetermined geometrical situations;

e) means for introducing at least one supplementary control point into said series between said two successive control points when said validity criterion is not verified, for transforming a contour fragment terminating at the supplementary control point, testing each resulting straight fragments for conformance with said topological validity criterion, and repeating the introducing, transforming and testing until said validity criterion is verified;

f) a calculation and comparison circuit for validating said transformation responsive to the approximation error resulting from this transformation being less than a given error;

g) means for applying the transformation by said means for transforming, testing and introducing to each pair of successive control points until the contour loop is completely closed again; and

h) means for coding the polygonal contour formed by the succession of segments thus obtained.

4. A device as claimed in claim 3, wherein said topological validity criterion is exclusive of determination of a distance of a point on said contour fragment from said straight segment.

5. A device as claimed in claim 4, wherein said at least one topological criterion includes:

said straight segment does not intersect the contour being considered at points outside said contour fragment,

said straight segment does not intersect another region not adjoining the current region being considered,

substitution of said straight segment does not eliminate a different region included in said current region, and

said straight segment is not tangent to yet another region thereby constricting yet a different region so as to cut said yet a different region into two distinct regions.

6. A device as claimed in claim 5, further comprising means for controlling re-initialization of the transformation procedure, including the same testing for at least one topological validity criterion, for each set of two successive straight segments which are bounded by original control points.

7. A device as claimed in claim 3, further comprising means for controlling re-initialization of the transformation procedure, including the same testing for at least one topological validity criterion, for each set of two successive straight segments which are bounded by original control points.

8. A device as claimed in claim 7, characterized in that said means for detecting control points comprises, for each contour of the detected region,

a circuit for tracking this contour,

a memory for storing coordinates of image points successively encountered on this contour,

a circuit for detecting on this contour triplet points which are situated at the area of contact of at least three regions, said triplet points forming said original control points, and

a memory for storing said triplet points which is also connected to the output of the memory for storing the coordinates of the contour of the current region being considered.