Method for rendering digital radiographic images for display based on independent control of fundamental image quality parameters
View Patent ↗A system for enhancing a digital image. The system includes: means for providing a digital image; means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows: a lowest frequency band image which represents large-sized features in the digital image; a low-to-mid frequency band image which represents mid-sized features of the digital image; a mid-to-high frequency band image which represents the small-sized features in the digital image; and a highest frequency band which represents very fine detail in the digital image; means for manipulating said low-to-mid frequency band image to produce a contrast effect without affecting the overall dynamic range of said digital image; means for multiplying each of said high-frequency band images with a gain factor; means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.
1. A system for enhancing a digital image comprising:
means for providing a digital image;
means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:
a lowest frequency band image which represents large-sized features in the digital image;
a low-to-mid frequency band image which represents mid-sized features of the digital image;
a mid-to-high frequency band image which represents the small-sized features in the digital image; and
a highest frequency band which represents very fine detail in the digital image;
means for manipulating said low-to-mid frequency band image to produce a contrast effect without affecting the overall dynamic range of said digital image;
means for multiplying each of said high-frequency band images with a gain factor;
means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and
means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.
2. A system for enhancing a digital image comprising:
means for providing a digital image;
means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:
a lowest frequency band image which represents large-sized features in the digital image;
a low-to-mid frequency band image which represents mid-sized features of the digital image;
a mid-to-high frequency band image which represents the small-sized features in the digital image; and
a highest frequency band which represents very fine detail in the digital image;
means for multiplying each of said high-frequency band images with a gain factor; wherein said gain factor which multiplies said low-to-mid frequency band image is derived from a detail contrast control and a dynamic range control;
means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and
means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.
3. The system of claim 2 wherein said detail contrast control is a function of said lowest frequency band image (which represents average log exposure).
4. The system of claim 3 wherein the functional form of said detail contrast control is a piecewise linear curve with breakpoints.
5. The system of claim 4 wherein said breakpoints are first assigned in density and then mapped to log exposure breakpoints via said tone-scale curve providing density dependent control of the detail contrast of said image.
6. The system of claim 2 wherein manipulation of said detail contrast control does not affect the overall dynamic range or sharpness of small or fine detail of said image.
7. A system for enhancing a digital image comprising:
means for providing a digital image;
means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:
a lowest frequency band image which represents large-sized features in the digital image;
a low-to-mid frequency band image which represents mid-sized features of the digital image;
a mid-to-high frequency band image which represents the small-sized features in the digital image; and
a highest frequency band which represents very fine detail in the digital image;
means for multiplying each of said high-frequency band images with a gain factor; wherein said gain factor which multiplies said mid-to-high frequency band image is derived from a sharpness control and said gain factor which multiplies said low-to-mid frequency band image;
means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and
means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.
8. The system of claim 7 wherein said sharpness control is a function of said lowest frequency band image (which represents average log exposure).
9. The system of claim 8 wherein the functional form of said sharpness control is a piecewise linear curve with breakpoints.
10. The system of claim 9 wherein said breakpoints are first assigned in density and then mapped to log exposure breakpoints via said tone-scale curve providing density dependent control of the sharpness of small detail of said image.
11. A system for enhancing a digital image comprising:
means for providing a digital image;
means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:
a lowest frequency band image which represents large-sized features in the digital image;
a low-to-mid frequency band image which represents mid-sized features of the digital image;
a mid-to-high frequency band image which represents the small-sized features in the digital image; and
a highest frequency band which represents very fine detail in the digital image;
means for multiplying each of said high-frequency band images with a gain factor; wherein said gain factor which multiplies said highest frequency band image is derived from a fine detail control and said gain factor which multiplies the mid-to-high frequency band image;
means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and
means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.
12. The system of claim 11 wherein said fine detail control is a function of the lowest frequency band image (which represents an average log exposure).
13. The system of claim 12 wherein the functional form of said fine detail control is a piecewise linear curve with breakpoints.
14. The system of claim 13 wherein said breakpoints are first assigned in density and then mapped to log exposure breakpoints via said tone scale curve providing density dependent control of the sharpness of the fine detail of said image.
15. A system for enhancing a digital image comprising:
means for providing a digital image;
means for decomposing the provided digital image into a multi-frequency band representation of four frequency bands as follows:
a lowest frequency band image which represents large-sized features in the digital image;
a low-to-mid frequency band image which represents mid-sized features of the digital image;
a mid-to-high frequency band image which represents the small-sized features in the digital image; and
a highest frequency band which represents very fine detail in the digital image;
means for multiplying each of said high-frequency band images with a gain factor; wherein said gain factors which multiply said higher frequency bands are a function of said lowest frequency band image;
means for summing together said unmodified low frequency band image and said modified high-frequency band images to produce a reconstructed digital image; and
means for mapping said reconstructed digital image through a tone-scale look-up table to map said reconstructed digital image to optical densities.