Removal of block encoding artifacts

1. A method of reducing artifacts in an image previously processed by block transform encoding comprising the steps of:

determining block boundaries in the image;

determining an approximate metric of block transform encoding artifact visibility;

adaptively filtering luminance to a degree dependent on the metric of block transform encoding artifact visibility;

adaptively adjusting local saturation variation to a degree dependent on the metric of block transform encoding artifact visibility; and

adaptively simulating high spatial frequency image detail to a degree dependent on the metric of block transform encoding artifact visibility.

2. The method of claim 1 wherein prior to adaptively filtering luminance, luminance values are interpolated across block boundaries.

3. The method of claim 2 wherein in conjunction with adaptively filtering luminance, chrominance is adaptively filtered.

4. A computer having software and hardware therein that is capable of executing and performing the method of claim 2 .

5. The method of claim 1 wherein in conjunction with adaptively filtering luminance, chrominance is adaptively filtered.

6. A computer having software and hardware therein that is capable of executing and performing the method of claim 1 .

7. A method of reducing artifacts in an image previously processed by block transform encoding comprising the steps of:

determining block boundaries in the image;

determining an approximate metric of block transforming encoding artifact visibility;

adaptively filtering luminance with a filter to a degree dependent on the metric of block transform encoding artifact visibility;

adaptively increasing local chrominance contrast to a degree dependent on the metric of block transform encoding artifact visibility; and

adaptively simulating high frequency image detail by sharpening and adding noise to a degree dependent on the metric of block transform encoding artifact visibility.

8. The method of claim 7 wherein prior to adaptively filtering luminance, luminance values are interpolated across block boundaries.

9. The method of claim 8 wherein after adaptively filtering luminance, chrominance is adaptively filtered.

10. A computer having software and hardware therein that is capable of executing and performing the method of claim 9 .

11. The method of claim 7 wherein after adaptively filtering luminance, chrominance is adaptively filtered.

12. A computer having software and hardware therein that is capable of executing and performing the method of claim 7 .

13. A method of reducing artifacts in an image previously processed by block transform encoding comprising:

determining a block boundary in the image, the block boundary being centered around a center pixel having a chrominance value;

selecting a median filter window based on luminance texture of pixels within the block boundary; and

replacing the chrominance value of the center pixel with a median chrominance value of pixels within the median filter window.

14. A computer having software and hardware therein that is capable of executing and performing the method of claim 13 .

15. A computer program storage medium readable by a computer system and encoding a computer program for executing a computer process that reduces artifacts in an image previously processed by block transform encoding, the computer process comprising:

determining block boundaries in the block transform encoded image;

determining an approximate metric of block transform encoding artifact visibility;

adaptively filtering luminance in the block transform encoded image to a degree dependent on the metric of block transform encoding artifact visibility;

adaptively adjusting local saturation variation in the block transform encoded image to a degree dependent on the metric of block transform encoding artifact visibility; and

adaptively simulating high spatial frequency image detail in the block transform encoded image to a degree dependent on the metric of block transform encoding artifact visibility.

16. A computer program storage medium readable by a computer system and encoding a computer program for executing a computer process that reduces artifacts in an image previously processed by block transform encoding, the computer process comprising:

determining block boundaries in the block transform encoded image;

determining an approximate metric of block transform encoding artifact visibility;

adaptively filtering luminance in the block transform encoded image with a filter to a degree dependent on the metric of block transform encoding artifact visibility;

adaptively increasing local chrominance contrast in the block transform encoded image to a degree dependent on the metric of block transform encoding artifact visibility; and

adaptively simulating high frequency image detail in the block transform encoded image to a degree dependent on the metric of block transform encoding artifact visibility by sharpening the block transform encoded image and adding noise to the block transform encoded image.

17. A computer program storage medium readable by a computer system and encoding a computer program for executing a computer process that reduces artifacts in an image previously processed by block transform encoding, the computer process comprising:

determining block boundaries in the block transform encoded image;

adaptively filtering luminance within the block boundaries of the block transform encoded image; and

adaptively adjusting local saturation variation within the block boundaries of the block transform encoded image.

18. A computer program storage medium readable by a computer system and encoding a computer program for executing a computer process that reduces artifacts in an image previously processed by block transform encoding, the computer process comprising:

determining a block boundary in the image, the block boundary being centered around a center pixel having a chrominance value;

selecting a median filter window based on luminance texture of pixels within the block boundary; and

replacing the chrominance value of the center pixel with a median chrominance value of pixels within the median filter window.