US 5,745,660 A · Image rendering system and method for generating stochastic threshold arrays for use therewith

Abstract

An image rendering system, for generating discrete tone image data representing a continuous-tone image for rendering by a rendering device, the image rendering system includes a stochastic threshold array generating arrangement and an image data processing section. The stochastic threshold array generating arrangement generates a plurality of stochastic threshold arrays from a random seed pattern that have been subsequently optimized to reduce image artifacts in the rendering of tones. Each pattern is optimized to reflect (i) a selected trade-off between grain and possible mottle in the rendered image, (ii) distortions introduced by the rendering device in rendering an image defined by the pattern and an observer in viewing the image, and (iii) boundary effects so that the patterns, when tiled together, have optimal visual characteristics proximate their respective edges. The image data processing section processes the continuous tone image data in relation to the stochastic threshold arrays generated by the stochastic threshold array generating arrangement. The image data processing section may be used to either randomly tile, or tile in an ordered way, the stochastic threshold arrays over the continuous-tone image data and generates the discrete tone image data in response to correspondingly positioned pixels of the continuous-tone image data and threshold values of the stochastic threshold arrays.

Claims64

Dependent claims

An image rendering system for generating discrete tone image data of an image for representing continuous tone image data to be rendered by a rendering device, the image rendering system comprising:

A. a stochastic threshold array library for storing a plurality of stochastic threshold arrays generated from individual seed patterns each corresponding to a predetermined tone of the image, each said seed pattern optimized to reflect corresponding predetermined grain/mottle trade-off conditions and optimal visual tiling characteristics when said seed pattern is tiled with itself;
and
B. an image data processing section for processing the continuous tone image data in relation to said stochastic threshold arrays, and for retrieving one said stochastic threshold array for one of the predetermined grain/mottle trade-off conditions, as selected by an operator, from said stochastic threshold array library, tiling the retrieved stochastic threshold array over the continuous-tone image data and generating the discrete tone image data in response to correspondingly positioned pixels of the continuous-tone image data and threshold values of the tiled stochastic threshold array.

An image rendering system for generating discrete tone image data representing continuous-tone image data for rendering by a rendering device, the image rendering system comprising:

A. a stochastic threshold array library for storing a plurality of stochastic threshold arrays generated from individual seed patterns optimized to have optimal visual tiling characteristics when randomly tiled together;
and
B. an image data processing section for processing the continuous tone image data in relation to the stochastic threshold arrays, randomly retrieving the stochastic threshold arrays from said stochastic threshold array library, tiling said retrieved stochastic threshold arrays randomly over the continuous-tone image data and generating the discrete tone image data in response to both correspondingly positioned pixels of the continuous-tone image data and threshold values of the tiled stochastic threshold arrays.

A stochastic threshold array generating subsystem for generating a plurality of stochastic threshold arrays for use in connection with generation of output image data from continuous tone image data for rendering by a rendering device, said stochastic threshold array generating subsystem comprising:

A. a stochastic pattern generator for generating a plurality of optimized stochastic patterns each from a respective seed stochastic pattern, at least one of said optimized stochastic patterns being generated in response to both said respective seed stochastic pattern and a previously generated stochastic pattern, said at least one pattern, when tiled with others of said optimized stochastic patterns, having optimal visual tiling characteristics proximate to respective edges of said tiled patterns;
and
B. a stochastic threshold array generator for generating the stochastic threshold arrays from said optimized stochastic patterns generated by said stochastic pattern generator.

A. an optimized stochastic pattern generator for generating an optimized stochastic pattern from a seed stochastic pattern comprising:
i. an initial stochastic pattern generator for generating an initial stochastic pattern;
and
ii. a stochastic pattern optimizer for optimizing the initial stochastic pattern comprising:
a. an error map generator for generating an error map reflecting differences between a stochastic pattern provided thereto and a rendering device filtered stochastic pattern that represents processing performed by the rendering device in rendering an image followed by psychovisual processing as performed by an observer in viewing the image and a neighborhood filtered stochastic pattern which identifies and penalizes features associated with mottle, respective contributions of the rendering device filtered stochastic pattern and the neighborhood filtered stochastic pattern to the error map being determined by respective complementary weighting factors, differing weighting factors being used during optimizing for the stochastic threshold arrays thereby to provide differing grain/mottle tradeoff conditions;
b. an updated stochastic pattern generator for generating an updated stochastic pattern in relation to the error map generated during the iteration;
and
c. an iteration control for controlling the error map generator and the updated stochastic pattern generator through a series of iterations, the iteration control enabling the error map generator to use the updated stochastic pattern generated during an iteration as the stochastic pattern used in generating the error map during a subsequent iteration;
B. generating the stochastic threshold arrays from the optimized stochastic patterns.

6 more elements

An error map generator for generating an error map for use in generating updated stochastic patterns in connection with a stochastic pattern provided to the error map generator, the stochastic pattern to be used in connection with generation of a stochastic threshold array to be used in generating output image data from continuous-tone image data to be rendered by a rendering device, each stochastic pattern comprising a plurality of pixels, the error map generator comprising:

A. means for generating a rendering device error map which minimizes grain by identifying errors in connection with processing by the rendering device of an image represented by the stochastic pattern provided thereto in connection with rendering of large clusters of pixels;
B. a neighborhood error map generator for generating a neighborhood error map which minimizes mottle by identifying errors in connection with processing by the rendering device of said image represented by the stochastic pattern provided thereto in connection with rendering of small clusters of pixels;
and
C. a composite error map generator for generating a composite error map which provides a grain/mottle tradeoff in response to both the rendering device error map and the neighborhood error map.

1 more element

A method of generating an error map for use in generating updated stochastic patterns to be used in connection with generation of a stochastic threshold array to be used in generating output image data from continuous-tone image data to be rendered by a rendering device, each stochastic pattern comprising a plurality of pixels, the method comprising the steps of:

A. generating a rendering device error map which minimizes grain by identifying errors in connection with processing by the rendering device of an image represented by the stochastic pattern provided thereto in connection with rendering of large clusters of pixels;
B. generating a neighborhood error map which minimizes mottle by identifying errors in connection with processing by the rendering device of said image represented by the stochastic pattern provided thereto in connection with rendering of small clusters of pixels;
and
C. generating a composite error map which provides a grain/mottle tradeoff in response to both the rendering device error map and the neighborhood error map.

1 more element

Dependencies are inferred from the claim text.

Image rendering system and method for generating stochastic threshold arrays for use therewith

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Image rendering system and method for generating stochastic threshold arrays for use therewith

Life of this patent

Abstract

Claims64