Sigfredo I. Nin

Performing color space conversions with three-dimensional linear interpolation

Three-dimensionalinterpolation is suitable for many kinds of color space transformations. We examine and analyze several linear interpolation schemes-some standard, some known, and one novel. An interpolation algorithm design is divided into three parts: packing (filling the space of the input variable with sample points), extraction (selecting from the constellation of sample points those appropriate to the interpolation of a specific input point), and calculation (using the extracted values and the input point to determine the interpolated approximation to the outputpoint). We focus on regular (periodic) packing schemes. Seven principles govern the design of linear interpolation algorithms: 1) Each sample point should be used as a vertex of as many polyhedra as possible; 2) the polyhedra should completely fill the space; 3) polyhedra that share any part of a face must share the entire face; 4) the polyhedra used should have the fewest vertices possible; 5) polyhedra should be small; 6) in the absence of information about cuivature anisotropy, polyhedra should be close to regular in shape; and 7) polyhedra should be of similar size. A test for interpolation algorithm performance in performing actual color space conversions is described, and results are given for an example color space conversion using several linear interpolation methods. The extractions from cubic, body-centered-cubic, and face-centered-cubic lattices are described and analyzed. The results confirm Kanamoris claims for the accuracy of PRISM interpolation; it comes close to the accuracy of trilinear interpolation with roughly three-quarters the computations. The results show that tetrahedral interpolation, with close to half the computational cost of tnlinear interpolation, is capable of providing better accuracy. Of the tetrahedral interpolation techniques, one diagonal extraction from cubic packing is useful as a general-purpose color space interpolator...

Updates to the QBIC system

QBICTM (Query By Image Content) is a set of technologies and associated software that allows a user to search, browse, and retrieve image, graphic, and video data from large on-line collections. This paper discusses current research directions of the QBIC project such as indexing for high-dimensional multimedia data, retrieval of gray level images, and storyboard generation suitable for video. It describes aspects of QBIC software including scripting tools, application interfaces, and available GUIs, and gives examples of applications and demonstration systems using it.

Tetrahedral interpolation technique for color space conversion

Three-dimensional interpolation is often employed to minimize calculations when approximating mathematically defined complex functions or producing intermediate results from sparse empirical data. Both situations occur when converting images from one device- independent color space to another, or converting information between device-dependent and device-independent color spaces; this makes three-dimensional interpolation an appropriate solution to many kinds of color space transformations. Interpolation algorithms can be analyzed by considering them as consisting of three parts: packing, in which the domain of interest of the input space is populated with sample points; extraction, which consists of selecting the sample points necessary to approximate the function for a particular input value; and calculation, which accepts the input point and the extracted points and carries out calculations to approximate the function. Those algorithms that extract four points and perform tetrahedral interpolation yield the fewest calculations. The paper presents a test for interpolation algorithm accuracy, and provides a normalization which allows various packing and extraction schemes to be compared. When subjected to the normalized accuracy test, different packing and extraction schemes yield different accuracies. The paper describes a packing and an extraction algorithm that yields accurate results for many conversions. The performance of this scheme is compared to that of several well-known packing and extraction algorithms.

Printing CIELAB images on a CMYK printer using trilinear interpolation

The Color Rendering project at IBM Almaden Research Center is examining the problem of how to display and print quality color images. For this work we need a printer calibrated to a device independent color space. In this paper, we describe a system for printing CIELAB images on a CMYK printers, and focus particularly on calibration methods. We use tri-linear interpolation to convert CIELAB colors to CMY or CMYK colorants. We obtain the interpolation table by inverting a tetrahedral linear interpolation of a calibration table constructed by measuring printed color patches. Since tetrahedral interpolation has a simple analytical inverse, we can produce the inverted table much more quickly than with the numerical methods needed to invert a multilinear interpolation, even though we have to measure more patches to obtain the same accuracy. To cover the full printer gamut, we found it necessary to add some out-of-gamut entries to the inverted interpolation table. These entries must be obtained by extrapolation, and increase the errors interpolating colors on and near the gamut surface. To date we have calibrated a DuPont 4Cast to print CIELAB colors using CMY colorants. We discuss our results with this calibration, how we propose to add black, and how we fit gamut mapping into the processing.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Enabling secure distribution of digital media to SD-cards

As the marketplace for digital media increases we witness the rise of new media distribution models where timely delivery, convenience, privacy and personalization are essential features of competitive offerings. Consumers are looking for innovative ways to access content in a service-oriented manner that suits their mobile life style. This paper describes a prototype standard-based system that allows the secure and fast download of content to SD-Card-enabled consumer devices. Content is protected by Content Protection for Recordable Media (CPRM) technology; specifically we use CPRM SD-Video. Our prototype shows Digital Media Terminals (DMT, also denoted kiosks) that enable innovative rental and purchase models. Our solution combines IBMs plug-in web services, Panasonics leading-edge devices and Porto Medias high-speed data transfer to Secure Digital Memory Flash Cards (SD-Cards).