Removal of block encoding artifacts
A method of reducing artifacts in an image previously processed by block transform encoding may comprise the steps of: determining block boundaries; determining an approximate metric of artifact visibility; optionally interpolating across block boundaries; adaptively filtering luminance; optionally adaptively filtering chrominance; adaptively adjusting local saturation variation; and adaptively simulating high spatial frequency image detail; wherein the adaptive steps are executed to an extent or in an amount depending on the metric or standard or measurement of artifact visibility.
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.