Sweeping spatial filter system and method
View Patent ↗A method of providing a spatially filtered version of an image by selectively modifying image pixel amplitudes as a predetermined function of spatial frequency components of the image pixels includes dividing an overall frequency range of the image into a plurality of constituent frequency ranges. The method provides, for each of the constituent frequency ranges, a spatial filter for receiving the image pixels and producing a filtered output representative of the spatial frequency components of the pixels that are within that constituent frequency range. The method further includes scaling each of the filtered outputs by a scaling factor specific to the associated spatial filter, so as to produce a scaled output. Finally, the method includes combining the scaled outputs to produce a composite output representative of the spatially filtered version of the image. The scaling factors may include a predetermined set of values for a particular filter response, or the scaling factors may be time-varying so that the filter response changes as a function of time.
1. A method of providing a spatially filtered version of an image by selectively modifying image pixel amplitudes as a predetermined function of spatial frequency components of the image pixels, comprising:
dividing an overall frequency range of the image into a plurality of constituent frequency ranges;
providing, for each of the constituent frequency ranges, a spatial filter that receives the image pixels and produces a filtered output representative of the spatial frequency components of the pixels that are within that constituent frequency range;
scaling image pixel amplitude values for each of the filtered outputs by a scaling factor specific to the associated spatial filter, so as to produce a scaled output; and,
combining the scaled outputs to produce a composite output representative of the spatially filtered version of the image
wherein the scaling factors vary as a function of time so as to sweep a pass-band having a predetermined bandwidth across the overall frequency range, such that image components characterized by frequencies within the pass-band are enhanced or passed without substantial attenuation.
2. A method according to claim 1 , wherein the constituent frequency ranges are defined by octaves, such that each constituent frequency range is one half as wide as the next larger constituent frequency range.
3. A method according to claim 1 , wherein the constituent frequency ranges are substantially contiguous.
4. A method according to claim 1 , wherein the constituent frequency ranges overlap one another.
5. A method according to claim 1 , wherein image components characterized by frequencies outside of the pass-band are substantially suppressed.
6. A method according to claim 1 , wherein image components characterized by frequencies outside of the pass-band are attenuated but not substantially suppressed.
7. A method according to claim 1 , wherein the predetermined bandwidth varies as a function of time.
8. A method according to claim 1 , wherein the scaling factors vary as a function of time so as to sweep two or more pass-bands, each having a predetermined bandwidth, across the overall frequency range, such that image components characterized by frequencies within each of the pass-bands are enhanced, or are passed without substantial attenuation.
9. A method according to claim 8 , wherein image components characterized by frequencies outside of the pass-band are substantially suppressed.
10. A method according to claim 8 , wherein image components characterized by frequencies outside of the pass-band are attenuated but not substantially suppressed.
11. A method according to claim 8 , wherein the predetermined bandwidth varies as a function of time.
12. A method according to claim 1 , wherein the spatial filter produces a filtered output as a predetermined function of a neighborhood of pixels.
13. A system for providing a spatially filtered version of an image by selectively modifying image pixel amplitudes as a predetermined function of spatial frequency components of the image pixels, comprising:
a frequency divider for dividing an overall frequency range of the image into a plurality of constituent frequency ranges;
for each of the constituent frequency ranges, (i) a spatial filter that receives the image pixels and produces a filtered output representative of the spatial frequency components of the pixels that are within that constituent frequency range, and (ii) a multiplier tat scales image pixel amplitude values for each of the filtered outputs by a scaling factor specific to the associated spatial filter, so as to produce a scaled output; and,
a combiner for combining the scaled outputs to produce a composite output representative of the spatially filtered version of the image
wherein the scaling factors vary as a function of time so as to sweep a passband having a predetermined bandwidth across the overall frequency range, such that image components characterized by frequencies within the passband are enhanced or passed without substantial attenuation.
14. A system according to claim 13 , wherein the constituent frequency ranges are defined by octaves, such that each constituent frequency range is one half as wide as the next larger constituent frequency range.
15. A system according to claim 13 , wherein the constituent frequency ranges are substantially contiguous.
16. A system according to claim 13 , wherein the constituent frequency ranges overlap one another.
17. A system according to claim 13 , wherein image components characterized by frequencies outside of the passband are substantially suppressed.
18. A system according to claim 13 , wherein image components characterized by frequencies outside of the passband are attenuated but not substantially suppressed.
19. A system according to claim 13 , wherein the predetermined bandwidth varies as a function of time.
20. A system according to claim 13 , wherein the scaling factors vary as a function of time so as to sweep two or more passbands, each having a predetermined bandwidth, across the overall frequency range, such that image components characterized by frequencies within each of the passbands are enhanced or passed without substantial attenuation.
21. A system according to claim 20 , wherein image components characterized by frequencies outside of the passband are substantially suppressed.
22. A system according to claim 20 , wherein image components characterized by frequencies outside of the passband are attenuated but not substantially suppressed.
23. A system according to claim 20 , wherein the predetermined bandwidth varies as a function of time.
24. A system according to claim 13 , wherein the spatial filter produces a filtered output as a predetermined function of a neighborhood of pixels.
25. A method of a spatially filtering an image, comprising:
providing a spatial filter for receiving an may of intensity values corresponding to the image, and for producing a plurality of filtered outputs, each of which represents the intensity values having frequency components within a predetermined frequency range;
scaling the intensity values for each of the filtered outputs by an associated scaling factor, so as to produce a plurality of scaled outputs; and,
combining the scaled outputs to produce a composite output representative of a spatially filtered version of the image
wherein the scaling factors vary as a function of time so as to sweep a passband having a predetermined bandwidth across the overall frequency range, such that mane components characterized by frequencies within the passband are enhanced, or passed without substantial attenuation.
26. A method according to claim 25 , wherein image components characterized by frequencies outside of the passband are substantially suppressed.
27. A method according to claim 25 , wherein image components characterized by frequencies outside of the passband are attenuated, but not substantially suppressed.
28. A method according to claim 25 , wherein the predetermined bandwidth varies as a function of time.
29. A method according to claim 25 , wherein the scaling factors vary as a function of time so as to sweep two or more passbands, each having a predetermined bandwidth, across the overall frequency range, such that image components characterized by frequencies within each of the passbands are enhanced, or passed without substantial attenuation.
30. A method according to claim 29 , wherein image components characterized by frequencies outside of the passband are substantially suppressed.
31. A method according to claim 29 , wherein image components characterized by frequencies outside of the passband are attenuated but not substantially suppressed.
32. A method according to claim 29 , wherein the predetermined bandwidth varies as a function of time.