Multi-Dimensional look-up table generation via adaptive node selection based upon color characteristics of an input image
First Claim
1. A method for multi-dimensional look-up table generation via adaptive node selection based upon characteristics of an input image, the method comprising:
- receiving, from an image acquisition system, image data representing an input image, said image data comprising a set S of input values of at least a region of said input image, said input values determined to be statistically representative of color values in said input image;
obtaining, from a significance function generator, a significance function describing a relative importance of a transformation accuracy of input values in S to a multi-dimensional look-up table useful for transforming said input values from an input color space to an output color space, said multi-dimensional look-up table comprising a multi-dimensional grid having a node located at each intersection thereof, output color values being stored at each node location, each node being accessible by an input index value, said input values being used to determine respective input index values;
applying, using a dampening function generator, a distance weighting function to said significance function to produce a distance-weighted significance function, said distance weighting function balancing said significance function against a relative positioning of all of nodes in said multi-dimensional look-up table, said distance weighting function controlling a distance between adjacent nodes and comprises;
d(x,y)≧
0,∀
x,yε
V, and d(x,y)=0x=nmax;
andperforming, using an image processing system;
determining a significance value for said input values in set S using said distance-weighted significance function;
sorting said significance values for all inputs in S;
for each of a predetermined number of nodes;
identifying a location in said multi-dimensional look-up table where the input value has a maximum significance value; and
selecting a node at said identified location;
constructing a set of nodes N from said selected nodes;
generating a look-up table from said set of nodes N;
post-processing said set of nodes N to obtain any of a minimum spacing between nodes and a desired lattice size; and
providing said generated look-up table to an image output system configured to generate a hardcopy output image based upon output values retrieved from said generated look-up table.
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Abstract
What is provided is a system and method for node set construction and look-up table generation to transform image data in the form of color values of an input color image in an input color space to an output color space of an image output system. In the present method, node locations are selected based upon an importance value generated by a significance function which describes a relative importance of a given color value in the input image or a region thereof. A distance weighting function is also provided which is applied to the significance function to balance the significance of a given node against a relative positioning of all other nodes in the multi-dimensional grid. Nodes can be added or deleted according to methods also described herein. Accordingly, a multi-dimensional look-up table is generated wherein node tiling is based upon a significance of color values of an input image.
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Citations
18 Claims
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1. A method for multi-dimensional look-up table generation via adaptive node selection based upon characteristics of an input image, the method comprising:
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receiving, from an image acquisition system, image data representing an input image, said image data comprising a set S of input values of at least a region of said input image, said input values determined to be statistically representative of color values in said input image; obtaining, from a significance function generator, a significance function describing a relative importance of a transformation accuracy of input values in S to a multi-dimensional look-up table useful for transforming said input values from an input color space to an output color space, said multi-dimensional look-up table comprising a multi-dimensional grid having a node located at each intersection thereof, output color values being stored at each node location, each node being accessible by an input index value, said input values being used to determine respective input index values; applying, using a dampening function generator, a distance weighting function to said significance function to produce a distance-weighted significance function, said distance weighting function balancing said significance function against a relative positioning of all of nodes in said multi-dimensional look-up table, said distance weighting function controlling a distance between adjacent nodes and comprises;
d(x,y)≧
0,∀
x,yε
V, and d(x,y)=0x=nmax;and performing, using an image processing system; determining a significance value for said input values in set S using said distance-weighted significance function; sorting said significance values for all inputs in S; for each of a predetermined number of nodes; identifying a location in said multi-dimensional look-up table where the input value has a maximum significance value; and selecting a node at said identified location; constructing a set of nodes N from said selected nodes; generating a look-up table from said set of nodes N; post-processing said set of nodes N to obtain any of a minimum spacing between nodes and a desired lattice size; and providing said generated look-up table to an image output system configured to generate a hardcopy output image based upon output values retrieved from said generated look-up table. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
where α
is a positive, scalar value, and the distance between adjacent nodes being controlled by varying α
, such that, for a given x and y, an increase in α
results in a decrease in e−
α
∥
x−
y∥
2 and causes d(x, y) to approach 1.
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6. The method of claim 1, wherein post-processing said set of nodes N to obtain said minimum spacing between nodes comprising eliminating at least one of said selected nodes to achieve a minimum allowable node spacing along a kth dimension.
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7. The method of claim 6, wherein eliminating at least of said selected nodes comprises:
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wherein M is a number of nodes selected, nj, j=1, 2, . . . , M, wherein n1, n2, . . . , nM are sorted scalar values of nodes in said kth dimension, such that;
n1≦
n2≦
. . . nM,wherein pk(n) is a separable weighting function for said kth dimension obtained from a joint multi-dimensional profile p(x), wherein n0=nmin and nm+1=nmax, wherein p(nmin)=p(nmax)=1, A) selecting Δ
min as a minimum allowable spacing along said kth dimension;B) adding boundary nodes nmin and nmax to node set N to obtain node set N′
;C) for each node in node set N′
, beginning with nj=nmax;i) determining whether nj+1−
nj<
Δ
min for a node having a highest significance value, and if not, said spacing between node levels being sufficient; andii) otherwise determining whether p(nj+1)>
p(nj) at node level nj, and if so retaining node level nj+1 and eliminating node level nj, otherwise retaining node level nj and eliminating node level nj+1; andD) generating node set N″
having said selected minimum allowable spacing.
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8. The method of claim 1, wherein post-processing said set of nodes N to obtain a desired lattice size comprises adding at least one node between two of said selected nodes wherein a same number of nodes levels is required along a kth dimension.
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9. The method of claim 8, wherein adding at least one node between two of said selected nodes comprises:
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wherein M is a number of nodes selected, node nj, j=1, 2, . . . M, wherein Pk is a size of an input look-up table in said kth dimension such that Pk≧
M makes a lattice of size P1×
P2×
P3,wherein n1 through nN are sorted scalar values of nodes along said kth dimension, with N<
Pk,A) adding boundary values nmin and nmax to node set N to obtain node set N′
;B) repeating, for each node in node set N″
, until n*=nM;i) determining node n*=(nj nj+1)/2; and ii) inserting node n* between nodes nj and nj+1; and C) generating a node set N′
″
having a final lattice of size;
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10. A system for multi-dimensional look-up table generation via adaptive node selection based upon characteristics of an input image, the method comprising:
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an image acquisition system configured to receive image data representing an input image, said image data comprising a set S of input values of at least a region of said input image, said input values determined to be statistically representative of color values in said input image; a significance function generator configured to provide a significance function describing a relative importance of a transformation accuracy of input values in S to a multi-dimensional look-up table useful for transforming said input values from an input color space to an output color space, said multi-dimensional look-up table comprising a multi-dimensional grid having a node located at each intersection thereof, output color values being stored at each node location, each node being accessible by an input index value, said input values being used to determine respective input index values; applying, using a dampening function generator, a distance weighting function to said significance function to produce a distance-weighted significance function, said distance weighting function balancing said significance function against a relative positioning of all of nodes in said multi-dimensional look-up table, said distance weighting function controlling a distance between adjacent nodes and comprises;
d(x,y)≧
0,∀
x,yε
V, and d(x,y)=0x=nmax;an image processing system configured to perform; determining a significance value for said input values in set S using said distance-weighted significance function; sorting said significance values for all inputs in S; for each of a predetermined number of nodes; identifying a location in said multi-dimensional look-up table where the input value has a maximum significance value; and selecting a node at said identified location; constructing a set of nodes N from said selected nodes; and generating a look-up table from said set of nodes N; post-processing said set of nodes N to obtain any of a minimum spacing between nodes and a desired lattice size; and an image output system configured to generate a hardcopy output image based upon output values retrieved from said generated look-up table. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification