Method and apparatus for region and texture coding

• US 5,204,920 A
• Filed: 02/12/1992
• Issued: 04/20/1993
• Est. Priority Date: 01/12/1990
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Moran, David, Morris, Octavius J.
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US07/836,178
• Time in Patent Office: 433 Days
• Field of Search: 382/17, 382/22, 382/54, 382/56, 358/428, 358/463-464, 358/466, 358/467
• US Class Current: 382/166
• 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 luminance signal (Y) is applied to a segmentation device (2) which subjects the signal to a segmentation algorithm to produce a region image signal which is then encoded in a region image encoder (3). The region image signal is also applied to a region post-processor (4) in which an adapted smooth function is added to the region signal. The resulting modified region image signal is subtracted in subtractor (5) from the luminance signal to produce a texture signal which is encoded by a texture image encoder (6). The encoded signals are conveyed via a data channel (9) to respective region (12) and texture (14) image decoders and the recovered region image signal is post-processed in a processor (13) in the same manner as with processor (4). The resulting modified region image signal and the recovered texture image signal are added in an adder (15) to produce a reconstructed luminance signal. The smoothing function takes account of step edge height between adjacent regions and the width of the regions, so that it can be applied to all contour edges without having to identify and avoid those which are erroneous with respect to the luminance signal.

Claims

1. A method of processing a picture signal for conveyance by a transmission path or via a storage medium, said method comprising:

(i) receiving a picture signal which corresponds to luminous intensities in a picture;

(ii) subjecting said picture signal to a segmentation algorithm to derive a region signal corresponding to a profile of step edges of adjoining closed regions of contrasting luminous intensities in said picture;

(iii) post-processing the original region signal derived in (ii) to produce a modified region signal which is more free of false step edges in said profile than is the initial region signal; and

(iv) producing a texture signal which corresponds to the difference between the received picture signal and the modified region signal produced in (iii);

characterized in that the post-processing of the original region signal in (iii) comprises;

(v) deriving a smoothing function which is adapted to the contour of each of the step edges of said original region signal, such adaptation for any step edge being based on the height of such step edge and the widths of the closed regions of contrasting intensities adjacent thereto; and

(vi) adding the smoothing function derived in (v) to said original region signal to produce said modified region signal.

2. A method as claimed in claim 1, wherein the gradient of said smoothing function at a step edge of a region is dependent on the step edge size.

3. A method as claimed in claim 2, wherein the said smoothing function is a polynomial providing the approximation

4. A method as claimed in claim 1, wherein the gradient of said smoothing function at a step edge of a region is dependent upon the width of such region.

5. A method as claimed in claim 2, wherein the gradient of said smoothing function at a step edge of a region is dependent upon the width of such region.

6. A method as claimed in claim 3, wherein the gradient of said smoothing function at a step edge of a region is dependent upon the width of such region.

7. An apparatus for processing a picture signal for conveyance by a transmission path or via a storage medium, said apparatus comprising:

means for receiving a picture signal which corresponds to luminous intensities in a picture;

means for subjecting said picture signal to a segmentation algorithm to produce a region signal corresponding to a profile of step edges of adjoining closed regions of contrasting luminous intensities in said picture;

means for post-processing the original region signal to produce a modified region signal which is more free of false step edges in said profile than is the original region signal; and

means for producing a texture signal which corresponds to the difference between the received picture signal and the modified region signal;

characterized in that said means for post-processing the original region signal comprises;

means for deriving a smoothing function which is adapted to the contour of each of the step edges of said original region signal, such adaptation for any step edge being based on the height of such step edge and the widths of the closed regions of contrasting intensities adjacent thereto; and

means for adding said smoothing function to said region signal to derive said modified region signal.

8. An apparatus as claimed in claim 7, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent on the step edge size.

9. An apparatus as claimed in claim 8, wherein the said smoothing function produced by said function producing means is a polynomial providing the approximation

10. An apparatus as claimed in claim 7, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent upon the width of such region.

11. An apparatus as claimed in claim 8, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent upon the width of such region.

12. An apparatus as claimed in claim 9, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent upon the width of such region.

13. A method of recovering a picture signal received in the form of a first picture signal component and a second picture signal component, the first component being related to a region signal corresponding to a profile of step edges of adjoining closed regions of contrasting luminous intensities in a picture represented by said picture signal, and a second component being related to a texture signal corresponding to a texture characteristic of said picture signal;

said method comprising;

(i) receiving said first picture signal component and recovering said region signal therefrom;

(ii) receiving said second picture signal component and recovering said texture signal therefrom;

(iii) post-processing the original region signal recovered in (i) to produce a modified region signal which is more free of false step edges in said profile than is the original region signal; and

(iv) producing a recovered picture signal by combining the modified region signal produced in (iii) and the texture signal recovered in step (ii);

characterized in that the post-processing of the original region signal in (iii) comprises;

(v) deriving a smoothing function which is adapted to the contour of each of the step edges of the original region signal, such adaptation for any step edge being based on the height of such step edge and the widths of the closed regions of contrasting intensities adjacent thereto; and

(vi) adding the smoothing function derived in (v) to said original region signal to produce said modified region signal.

14. A method as claimed in claim 13, wherein the gradient of said smoothing function at a step edge of a region is dependent on the step edge size.

15. A method as claimed in claim 14, wherein the said smoothing function is a polynomial providing the approximation

16. A method as claimed in claim 13, wherein the gradient of said smoothing function at a step edge of a region is dependent upon the width of such region.

17. An apparatus for recovering a picture signal received in the form of a first picture signal component and a second picture signal component, the first component being related to a region signal corresponding to a profile of step edges of adjoining closed regions of contrasting luminous intensities in a picture represented by said picture signal, and the second component being related to a texture signal corresponding to a texture characteristic of said picture signal;

said apparatus comprising;

means for receiving said first picture signal component and recovering said region signal therefrom;

means for receiving said second picture signal component and recovering said texture signal therefrom;

means for post-processing the original region signal to produce a modified region signal which is more free of false step edges in said profile than is the original region signal; and

means for producing a recovered picture signal by combining the modified region signal with said texture signal;

characterized in that said means for post-processing the original region signal comprises;

means for producing a smoothing function which is adapted to the contour of each of the step edges of the original region signal, such adaptation for any step edge being based on the height of such step edge and the widths of the closed regions of contrasting intensities adjacent thereto; and

means for adding said smoothing function to said original region signal to produce said modified region signal.

18. An apparatus as claimed in claim 17, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent on the step edge size.

19. An apparatus as claimed in claim 18, wherein the said smoothing function produced by said function producing means is a polynomial providing the approximation

20. An apparatus as claimed in claim 17, wherein the gradient of said smoothing function produced by said function producing means at a step edge of a region is dependent upon the width of such region.