Method and apparatus for image processing and on-vehicle camera apparatus
An image processing apparatus that includes an edge-enhancement filter that enhances sharpness of an image is provided. The edge-enhancement filter includes distance calculators that calculate values of a distance between a target pixel and an optical center of a captured image in two or more axial directions, edge detection filters that detect edge amounts in two directions, multipliers that multiplies each of the edge amounts detected by the edge detection filters by one of the distance values of a corresponding one of the axial directions, a first adder that adds outputs of the multipliers together, and a second adder that adds a pixel value of the target pixel and an output of the first adder. A coring unit can be interposed between the first adder and the second adder if necessary.
1. An image processing apparatus comprising edge-enhancement filter unit that enhances sharpness of an image, wherein
the edge-enhancement filter unit includes:
a distance calculating unit configured to calculate distance values, which are values of a distance between a target pixel and an optical center of a captured image in at least two axial directions including a first axial direction and a second axial direction;
an edge detection filter corresponding to each of the axial directions, wherein each of the edge detection filter is configured to detect an edge amount in a corresponding one of at least two directions on an direction-by-direction basis, the at least two directions including the first axial direction and the second axial direction;
a multiplying unit corresponding to each of the edge detection filters, wherein each of the multiplying units is configured to multiply the edge amount detected at a corresponding one of the edge detection filters by the distance value calculated by the distance calculating unit for a corresponding one of the axial directions, including a first multiplying unit configured to multiply the edge amount detected in the first axial direction by the edge detection filter by the distance value in the first axial direction calculated by the distance calculating unit and a second multiplying unit configured to multiply the edge amount detected in the second axial direction by the edge detection filter by the distance value in the second axial direction calculated by the distance calculating unit;
a first adding unit that adds up outputs of the multiplying units together; and
a second adding unit configured to add a pixel value of the target pixel to an output of the first adding unit.
2. The image processing apparatus according to claim 1 , wherein the edge detection filters are two in number, one of the edge detection filters detects edge in a lateral direction of an image frame and other one of the edge detection filters detects edge in a longitudinal direction of the image frame.
3. The image processing apparatus according to claim 1 , wherein the edge-enhancement filter unit further includes, at a subsequent stage of the first adding unit, a coring unit that outputs zero when the output of the first adding unit is equal to or lower than a predetermined threshold value.
4. The image processing apparatus according to claim 1 , wherein the edge-enhancement filter unit further includes, at a subsequent stage of each of the multiplying unit, a coring zero when an output of a corresponding one of the multiplying unit is equal to or lower than a predetermined threshold value.
5. The image processing apparatus according to claim 1 , wherein the edge-enhancement filter unit further includes, at a subsequent stage of each of the edge detection filters, a coring unit that outputs zero when an output of a corresponding one of the edge detection filters is equal to or lower than a predetermined threshold value.
6. The image processing apparatus according to claim 1 , wherein the edge-enhancement filter unit further includes, at a subsequent stage of the distance calculating unit, a third adding unit corresponding to each of the axial directions configured to add a constant value to an output of the distance calculating unit.
7. The image processing apparatus according to claim 1 , wherein outputs of the distance calculating unit are asymmetrical about a center of the image.
8. The image processing apparatus according to claim 1 , further comprising, at a preceding stage of the edge-enhancement filter unit, a chrominance/luminance separating unit that separates image data into chrominance signals and a luminance signal, wherein the edge-enhancement filter unit receives the luminance signal and performs edge enhancement on the luminance signal.
9. The image processing apparatus according to claim 1 , wherein the image is captured by using a wide-view-angle optical system.
10. An image processing method comprising an edge-enhancement filtering step of enhancing sharpness of an image, wherein
the edge-enhancement filtering step includes:
a distance calculating step of calculating distance values, which are values of a distance between a target pixel and an optical center of a captured image in at least two axial directions including a first axial direction and a second axial direction;
an edge-detection filtering step of detecting edge amounts in at least two directions on an direction-by-direction, the at least two directions including the first axial direction and the second axial direction;
a multiplying step of multiplying each of the edge amounts detected at the edge-detection filtering step, which is detected in a corresponding one of the axial directions, by one of the distance values calculated at the distance calculating step, the multiplying step including multiplying the edge amount detected in the first axial direction by the edge-detection filtering step by the distance value in the first axial direction calculated by the distance calculating step and multiplying the edge amount detected in the second axial direction by the edge detection-filtering step by the distance value in the second axial direction calculated by the distance calculating step;
a first adding step of adding multiplication results obtained at the multiplying step together; and
a second adding step of adding a pixel value of the target pixel to an output of the first adding step.
11. The image processing method according to claim 10 , wherein the edge-detection filtering step includes calculating edge in two directions of a lateral direction and a longitudinal direction of an image frame.
12. The image processing method according to claim 10 , wherein the edge-enhancement filtering step includes, after the first adding step, a coring step of outputting zero when the output of the first adding step is equal to or lower than a predetermined threshold value.
13. The image processing method according to claim 10 , wherein the edge-enhancement filtering step includes, after the multiplying step, a coring step of outputting zero when an output for a corresponding one of the directions at the multiplying step is equal to or lower than a predetermined threshold value.
14. The image processing method according to claim 10 , wherein the edge-enhancement filtering step includes, after the edge detection filtering step, a coring step of outputting zero when an output of a corresponding one of the direction at the edge-detection filtering step is equal to or lower than a predetermined threshold value.
15. The image processing method according to claim 10 , wherein the edge-enhancement filtering step further includes, after the distance calculating step, a third adding step of adding a constant value to each output at the distance calculating step.
16. The image processing method according to claim 10 , wherein outputs of the distance calculating steps are asymmetrical about a center of the image.
17. The image processing method according to claim 10 , further comprising, before the edge-enhancement filtering step, a chrominance/luminance separating step of separating image data into chrominance signals and a luminance signal, wherein the edge enhancement filtering step includes performing edge enhancement on the luminance signal.
18. The image processing method according to claim 10 , wherein the image is captured by using a wide-view-angle optical system.
19. An on-vehicle camera apparatus comprising:
a wide-view-angle optical system;
an imaging device that reads an image captured at the wide-view-angle optical system;
the image processing apparatus according to claim 1 configured to process the image read by the imaging device to output a processed image; and
a display device that displays the processed image.