Xerox Corporation

Bank One, Na, As Administrative Agent

David H Marimont

Leonidas John Guibas

Eric Saund

Todd A Cass

Maureen C Stone

Andrew S Glassner

A system and method are provided to normalize colors in an image of a board surface so as to eliminate effects of variable illumination, and in the case of mosaic images, to eliminate visible seams between tiles. Each pixel is classified as foreground or background, where foreground pixels contain ink marks. An efficient smoothing process estimates the ideal background color of all pixels, including the foreground pixels. The estimated background color is used to normalize each pixel's color such that in the final image, artifacts arising from camera gain and uneven lighting of the board surface are eliminated.

System and method for color normalization of board images

A representation of a color image region is called a space-color separable (SCS) model because the spatial structure of the image region is represented separately from that of the color-space structure. The representation uses two functions, one to represent the region's spatial structure and another to represent its color-space structure. In one implementation, the spatial structure is represented by polynomials of arbitrary degree to map image locations to the parameter values of the color-space model which in turn maps these parameter values to a zero-, one-, two-, or three-dimensional linear subspace of color space. The representation is resolution-independent and can accommodate both transformations of image coordinates and transformation of color coordinates. In particular, the polynomial-linear implementation can easily accommodate both affine transformations of image coordinates and linear transformations of color coordinates. This flexibility makes it useful for a variety of applications in illustration and image editing systems. The invention combines several features: representing smooth shading or textures in color images; separating the spatial structure of the colors in the image from its color space structure; and enabling transformations of images and their colors by transforming the SCS model itself.

Representing a region of a color image using a space-color separable

The invention automatically produces a rendered image version of an original image that accurately represents perceptually distinguishable objects, surfaces and edges in the original image. The original image is first converted to a unique data structure representation called an image structure map (ISM) that accurately, compactly and explicitly represents the geometry, topology and signal properties of perceptually distinguishable regions in the original image. The ISM is a dynamic partition of the image induced by a set of image region boundaries, and includes, for each region in the original image, a region data item that indicates the region boundary data items that form the region and a signal property descriptor indicating the value of signals computed for image locations in the region. An automatic segmentation operation determines image region boundaries occurring in the original image by analyzing discontinuities in signal values of original image locations. The topology of the rendered image version is accurate because vertices (endpoints and intersections) of image region boundaries are represented in the ISM in machine representable values that result from modifying exact vertex values using a rounding operation that mathematically ensures topological and geometric consistency with the original image. The method is particularly useful for producing rendered image versions of full color, continuous tone photographic images, and for producing line drawings of such images. The ISM representation of an image is, in most cases, more compact than its original raster form, and serves as a useful representation for archiving the image.

Producing a rendered image version of an original image using an image

A data structure representation of an original image called an image structure map (ISM) accurately, compactly and explicitly represents the geometry, topology and signal properties of regions in an original image. In mathematical terms, the ISM is a partition of the original image induced by a set of image region boundaries. The ISM data structure includes, for each region in the original image, a region data item that indicates the region boundary data items that form the region and a signal property descriptor indicating the value of signals computed for or assigned to the region. Region boundary data items represent image region boundaries that are determined to occur in the original image as a result of analyzing signal properties of original image locations. Vertices (endpoints and intersections) of region boundary data items are represented in the ISM in machine representable values that result from modifying infinite precision vertex values using a rounding operation that mathematically ensures topological and geometric consistency with the original image. The image structure map includes a spatial image indexing data structure in the form of hierarchy of partitions of the original image of varying levels of detail that allows for efficient point location. An illustrated implementation of the data structure has the form of a vertical cell decomposition. The ISM may be implemented to permit dynamic modifications so that changes to regions resulting from the insertion or deletion of new or changed region boundaries may be made without recomputing the entire ISM.

Image structure map data structure for spatially indexing an imgage

The present invention produces a data structure that indicates a partition of a given input set of line segments in a plane using a technique that is mathematically robust, canonical and dynamic. The technique is robust because it assumes a finite precision model of computer arithmetic and rounds the endpoints and intersections of all line segments to representable points in a way that is globally topologically consistent with the input set of line segments and that keeps the position of each rounded line segment close to the position of the input segment. The technique is canonical because the output partition produced is a function of the set of segments currently present only, and not of the history of insertion and deletions. This canonical aspect of the technique is facilitated by storing the input unrounded line segments in the partition data structure so that they are associated with their rounded fragments. The technique is dynamic because input unrounded line segments may be incrementally added to and deleted from the data structure representation of the partition without recomputing the entire partition for each change. An illustrated implementation of the technique uses a randomized incremental approach that produces a partition having the form of a vertical cell decomposition.

Dynamic computation of a line segment arrangement using finite precision

A data structure representation of an image called an image structure map (ISM) accurately and explicitly represents the geometry, topology and signal properties of regions in an original image and allows for efficient and accurate spatial indexing of the image and those regions. The ISM may serve as the basis for an image interaction system in which a user interacts with a rendered view of an original image that is produced from the ISM data structure. The rendered view of the original image represents the geometry and topology of the original image as represented in the ISM. The user interacts with the rendered view to make alterations to, or to query, the structures in the ISM. The user may also modify the ISM by interacting directly with a displayed view of the original image. The user may further invoke automatic operations to be performed using the original image data structure that produce image region data, such as signal property descriptors and boundary data, that may be used to modify the ISM. An image interaction system implemented in this manner takes full advantage of automatic computation methods to capture the geometric and topological properties of an image while permitting a user to employ human perceptual skills to augment the automatic operations. An illustrated implementation of the system uses an ISM having the form of a vertical cell decomposition that is mathematically robust, topologically consistent with the original image and is able to be modified dynamically--that is, without recomputing the entire ISM when a change is made.

User-directed interaction with an image structure map representation of

Binary digital data is rendered on a surface, such as a sheet of paper, by printing a series of color patches on the sheet, with the 1 bits rendered as color patches of a first color and the 0 bits rendered as color patches of the second color. The color patches are arranged in a predetermined order along an axis on the surface. The second color relates to the first color by a fixed relationship in color space, whereby the absolute values of the first and second colors are immaterial to a detecting apparatus. The color patches can be intermixed with areas of a third color, the third color representing an average in color space of the first color and the second color.

Binary glyph codes based on color relationships

A method of rendering a color image on a designated output medium is disclosed which maps colors to the gamut of the designated output medium while preserving the semantic consistency of the object color and illumination information in the image. The method performs gamut mapping earlier in the image synthesis process than current gamut method methods, at the point where information about object primitives and their spectral attributes in a scene description is available, but after the fixed scene geometry has been determined by the rendering system. The method makes use of the output of a symbolic rendering system which produces symbolic pixel expressions, having basis spectra variables which represent the interplay of light and object primitives in the scene description, and spectral data having color information about the light and object primitives in the scene, and which is indexed to the basis spectra variables. The method performs spectral change calculations using the symbolic pixel expressions, the spectral data, and spectral information about the gamut of the specific output medium to determine the modifications to the original spectral data that need to be made to the individual object primitives in the scene in order to produce image pixel colors which are in the gamut of the output medium. The resulting image colors are locally and globally consistent with the semantics of the image, make effective use of as much of the available gamut of the display device as is possible, and require no further post-rendering gamut mapping prior to display or reproduction on the designated medium.

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Palo Alto, CA, United States of America

David H Marimont