Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2002-11-08
2004-09-28
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S613000, C345S614000, C345S629000, C345S589000, C345S592000, C382S269000
Reexamination Certificate
active
06798422
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a method and a filtering system for filtering edge directions in an edge orientation map detected from an interlaced or non-interlaced scan. The filtered edge directions can then be used in an image interpolation process to preserve the smoothness of the edges in the interpolated image.
Referring to
FIG. 1
, the meaning of the term “edge direction” can be seen. Along the edge direction, pixels' luminance values remain constant or change gradually, however, across the edge direction, pixels' luminance values change sharply.
Image interpolation is usually performed in both image de-interlacing and image scaling applications. There are various kinds of methods used for image interpolation. With most methods, one common problem is the degradation of edges such as the effects of serrate lines associated with the interpolated image. To overcome this problem, it is desirable to find edge directions in the image and to do image interpolation along those directions so that the smoothness of the edges can be preserved.
There have been a large number of methods published on edge detection, including edge location detection and edge direction detection. However, most edge detection methods are sensitive to image noise. In addition, the neighborhood of a given pixel in an image can have numerous cases for an edge detection method to process. As a result, it is common, if not inevitable, for an edge detection system to provide a certain percentage of false edge locations or wrong edge directions.
Meanwhile, the accuracy of the edge directions serves a crucial role when the directions are used in image applications such as de-interlacing or scaling. In edge direction based image de-interlacing, the edge direction may be detected at the position of each pixel to be interpolated. Then for edge pixels, interpolation can be performed along the edge directions to preserve the smoothness of the edges in the interpolated image. The same idea can be applied to image scaling as well. However, in these applications if a detected edge is false or if the edge direction is not correct, obvious error may be introduced into the interpolated image. Therefore, when edge directions are utilized in these kinds of applications, false edges or edges with wrong directions must be excluded before the edge information is used.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a filtering system for filtering edge directions, which overcome the above-mentioned disadvantages of the prior art methods and apparatus of this general type.
In particular, it is an object of the invention to provide a filtering method that can be applied to an edge orientation map obtained from an edge direction detection system. The filtering method should keep accurate edge directions and filter out false edges or edges with wrong directions.
To accomplish the object of the invention, a direction length filter is provided for performing a direction length filtering process. The direction length filter is used to filter the edge direction along the direction indicated by the edge direction. Along the current direction, neighboring edge directions are checked to see whether their orientations are similar to the current direction being checked. If the neighboring directions have very different orientations from the current direction, the current direction is filtered out. The assumption for this filtering is that a valid edge direction should be able to be extended and should therefore have a certain minimum length.
A direction width filter for performing a direction width filtering process may also be provided. The width of a direction in an edge orientation map is defined as the number of consecutive neighboring positions along the horizontal direction where the edge directions are close to the current one. The direction width filter is used to filter out edge directions in the edge orientation map that are too thin. If along the horizontal direction there are a certain minimum number of consecutive neighboring edge directions that have similar orientations to the current one, then the current direction is kept. Otherwise, the current direction is filtered out.
A direction smoother for performing a direction smoothing process may also be provided. The direction smoother is basically a low pass filter. When the direction smoother is applied to directions in an edge orientation map, the filter can smooth the changing of neighboring edge directions. This process is found to be effective in improving the visual quality of an image that is interpolated based on edge directions.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for filtering an edge direction. The method includes steps of: in a given row in an edge orientation map, selecting a given pixel having an edge direction; finding neighboring upper pixels having neighboring upper edge directions for the given pixel by traversing along the edge direction of the given pixel from the given pixel to a neighboring upper row of the edge orientation map; finding neighboring lower pixels having neighboring lower edge directions for the given pixel by traversing along the edge direction of the given pixel from the given pixel to a neighboring lower row of the edge orientation map; determining whether the edge direction of the given pixel can be extended to the neighboring upper row by checking an orientation similarity between the edge direction of the given pixel and the neighboring upper edge directions; determining whether the edge direction of the given pixel can be extended to the neighboring lower row by checking an orientation similarity between the edge direction of the given pixel and the neighboring lower edge directions; if the edge direction of the given pixel can be extended to both the neighboring upper row and the neighboring lower row, then assuming that the edge direction of the given pixel is valid; if the edge direction of the given pixel cannot be extended to the neighboring lower row, but the edge direction of the given pixel can be extended to one of the neighboring upper pixels, and a neighboring upper edge direction at the one of the neighboring upper pixels can be extended to a further neighboring upper row of the edge orientation map, then assuming that the edge direction of the given pixel is valid; if the edge direction of the given pixel cannot be extended to the neighboring upper row, but the edge direction of the given pixel can be extended to one of the neighboring lower pixels, and a neighboring lower edge direction at the one of the neighboring lower pixels can be extended to a further neighboring lower row of the edge orientation map, then assuming that the edge direction of the given pixel is valid; and otherwise, assuming that the edge direction of the given pixel is not valid.
In accordance with an added feature of the invention, the edge direction of the given pixel (x,y) is represented by d(x,y), and the step of finding the neighboring upper pixels includes using equations:
ƒ(
x,y
)=
d
(
x−
2
,c
u
(
x,y
)),
ƒ
l
(
x,y
)=
d
(
x−
2
,c
u
(
x,y
)−1), and
ƒ
r
(
x,y
)=
d
(
x−
2
,c
u
(
x,y
)+1), where
c
u
(
x,y
)=
y+d
(
x,y
)*2.
In addition, the step of finding the neighboring lower pixels includes using equations:
g
(
x,y
)=
d
(
x+
2,
c
d
(
x,y
)),
g
l
(
x,y
)=
d
(
x+
2
,c
d
(
x,y
)−1), and
g
r
(
x,y
)=
d
(
x+
2
,c
d
(
x,y
)+1), where
c
d
(
x,y
)=
y−d
(
x,y
)*2.
In accordance with an additional feature of the invention, the step of checking the orientation similarity between the edge direction of the given pixel and the neighboring upper edge directions includes:
a) defining a checking function chkup(x,y) as follows:
chkup
(
x
,
y
)
=
{
1
if
&LeftBracketingBar;
d
(
x
,
y
)
-
f
(
x
,
y
)
&RightBracketingBar;
&leq
Aiello Jeffrey P.
Bella Matthew C.
Myers Dawes Andras & Sherman LLP
Rahmjoo Mike
Samsung Electronics Co,. Ltd.
LandOfFree
Method and filtering system for filtering edge directions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and filtering system for filtering edge directions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and filtering system for filtering edge directions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3187990