Digital Color Imaging
TL;DR: A survey of color imaging can be found in this article, where the fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology, along with common mathematical models used for representing these devices.
Abstract: This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided.
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TL;DR: This work demonstrates a convenient, versatile approach to dynamically fine-tuning emission in the full colour range from a new class of core-shell upconversion nanocrystals by adjusting the pulse width of infrared laser beams and suggests that the unprecedented colour tunability from these nanocry crystals is governed by a non-steady-state upconverting process.
Abstract: Developing light-harvesting materials with tunable emission colours has always been at the forefront of colour display technologies. The variation in materials composition, phase and structure can provide a useful tool for producing a wide range of emission colours, but controlling the colour gamut in a material with a fixed composition remains a daunting challenge. Here, we demonstrate a convenient, versatile approach to dynamically fine-tuning emission in the full colour range from a new class of core-shell upconversion nanocrystals by adjusting the pulse width of infrared laser beams. Our mechanistic investigations suggest that the unprecedented colour tunability from these nanocrystals is governed by a non-steady-state upconversion process. These findings provide keen insights into controlling energy transfer in out-of-equilibrium optical processes, while offering the possibility for the construction of true three-dimensional, full-colour display systems with high spatial resolution and locally addressable colour gamut.
777 citations
TL;DR: This article presents an overview of existing map processing techniques, bringing together the past and current research efforts in this interdisciplinary field, to characterize the advances that have been made, and to identify future research directions and opportunities.
Abstract: Maps depict natural and human-induced changes on earth at a fine resolution for large areas and over long periods of time. In addition, maps—especially historical maps—are often the only information source about the earth as surveyed using geodetic techniques. In order to preserve these unique documents, increasing numbers of digital map archives have been established, driven by advances in software and hardware technologies. Since the early 1980s, researchers from a variety of disciplines, including computer science and geography, have been working on computational methods for the extraction and recognition of geographic features from archived images of maps (digital map processing). The typical result from map processing is geographic information that can be used in spatial and spatiotemporal analyses in a Geographic Information System environment, which benefits numerous research fields in the spatial, social, environmental, and health sciences. However, map processing literature is spread across a broad range of disciplines in which maps are included as a special type of image. This article presents an overview of existing map processing techniques, with the goal of bringing together the past and current research efforts in this interdisciplinary field, to characterize the advances that have been made, and to identify future research directions and opportunities.
674 citations
TL;DR: The proposed demosaicing algorithm estimates missing pixels by interpolating in the direction with fewer color artifacts, and the aliasing problem is addressed by applying filterbank techniques to 2-D directional interpolation.
Abstract: A cost-effective digital camera uses a single-image sensor, applying alternating patterns of red, green, and blue color filters to each pixel location. A way to reconstruct a full three-color representation of color images by estimating the missing pixel components in each color plane is called a demosaicing algorithm. This paper presents three inherent problems often associated with demosaicing algorithms that incorporate two-dimensional (2-D) directional interpolation: misguidance color artifacts, interpolation color artifacts, and aliasing. The level of misguidance color artifacts present in two images can be compared using metric neighborhood modeling. The proposed demosaicing algorithm estimates missing pixels by interpolating in the direction with fewer color artifacts. The aliasing problem is addressed by applying filterbank techniques to 2-D directional interpolation. The interpolation artifacts are reduced using a nonlinear iterative procedure. Experimental results using digital images confirm the effectiveness of this approach.
462 citations
TL;DR: An overview of the image processing pipeline is presented, first from a signal processing perspective and later from an implementation perspective, along with the tradeoffs involved.
Abstract: Digital still color cameras (DSCs) have gained significant popularity in recent years, with projected sales in the order of 44 million units by the year 2005. Such an explosive demand calls for an understanding of the processing involved and the implementation issues, bearing in mind the otherwise difficult problems these cameras solve. This article presents an overview of the image processing pipeline, first from a signal processing perspective and later from an implementation perspective, along with the tradeoffs involved.
368 citations
TL;DR: The proposed fully automated vector technique can be easily implemented in either hardware or software; and incorporated in any existing microarray image analysis and gene expression tool.
Abstract: Vector processing operations use essential spectral and spatial information to remove noise and localize microarray spots. The proposed fully automated vector technique can be easily implemented in either hardware or software; and incorporated in any existing microarray image analysis and gene expression tool.
348 citations
References
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IBM1
TL;DR: In this article, a tri-linear interpolation is used to convert CIELAB colors to CMY or CMYK colorants, and the interpolation table is obtained by inverting a tetrahedral linear interpolation of a calibration table constructed by measuring printed color patches.
Abstract: 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.
48 citations
23 Sep 1991
TL;DR: In this article, a model-based printing method and system for generating halftone output images corresponding to gray-scale-coded input signals is presented, which can be used to modify the grey-scale coded signals in such manner as to produce binary signals which, when applied to the printer, create halftones of enhanced quality.
Abstract: A model-based printing method and system for generating halftone output images corresponding to gray-scale-coded input signals. Models for individual two-level (e.g., black on white) printer types allow predicted printer error signals to be generated which can be used to modify the gray-scale coded signals in such manner as to produce binary signals which, when applied to the printer, create halftone images of enhanced quality. In an alternative embodiment binary signals are selected which minimize an error function based on the difference between (i) a predicted perceived image corresponding to the gray scale inputs as filtered by an eye-model filter and (ii) the halftone image resulting from filtering of the binary sequence by a filter modeling the printer followed by the eye-model filter.
47 citations
15 Apr 1994
TL;DR: The approach taken in this study reduces the dimensionality of the problem by subdividing the 7 inks into smaller groupings and generating an inktable which transforms color to ink.
Abstract: Adding RGB inks to the traditional set of CMYK inks increases the attainable color gamut. But the added complexity poses a challenge in generating suitable separations for rendering of color images. The approach taken in this study reduces the dimensionality of the problem by subdividing the 7 inks into smaller groupings. A series of 4 ink subsets from the 7 ink superset of CMYKRGB were individually characterized and a colorimetric transform from ink to color was obtained for each subset. In color space the 4 ink subsets represent adjacent and overlapping subgamuts of the 7 ink gamut. By utilizing these characterizations both individually and in combination with one another, an inktable which transforms color to ink was generated. In the darker tonal region, 4 inks/color permits access to regions of the full 7 ink gamut which are inaccessible to schemes employing 3 inks/color.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
47 citations
04 Aug 1993
TL;DR: In this article, a simple and straightforward Moire-free separation process is proposed for the color separation in the CIE-L*u*v* colorimetric spaces using the compound Neugebauer model.
Abstract: The present paper studies the chromaticity gamut of multi-color printing processes. Heptatone (7color) printing ‐ the most promising variant of multi-color printing ‐ offers a significantly larger gamut than a conventional CMYK printing process, approaching CRT and film gamuts. The behavior of the process in the device-independent CIE-XYZ and CIE-L*u*v* colorimetric spaces is explored using the compound Neugebauer model developped for this purpose. A simple and straightforward Moire ´-free separation process is proposed. The strong point of the proposed separation process is the fact that only 3 different screen layers are needed for any odd number of basic colors including black. In today’s printing industry, the 4-color CMYK (Cyan-Magenta-Yellow-blacK) printing process is the state-of-the art technology. Numerous problems related to color separation, printing device calibration, gray balance and color fidelity of the CMYK printing process have been studied since its invention by Alexander Murray in 1934 ([HUN87], [WYS82], [YUL67], [MOL88]). Although it proves satisfactory in a majority of cases, this printing process presents an important drawback: its chromaticity gamut is restricted when compared with the gamuts of CRT displays or real dyes. Some saturated colors such as orange, certain reds, violet, purple, blue and certain greens cannot be obtained by conventional CMYK printing. We propose to extend the printing process by introducing additional basic colors. This contribution modelizes the extension of the CMYK process to 5-color, 7-color and 9-color printing processes. The Heptatone (7-color) process has an excellent chromaticity gamut and is considered as the optimal tradeoff between printing quality and cost. The modelization of the color behavior of the CMYK printing process is presented in section 3. The modelization tool ‐ the Neugebauer equation ‐ is extended, in section 4, to the multi-color printing process. The results obtained by such a modelization are discussed in section 5. Finally, a scheme for a multi-color separation process is proposed in section 6. In our study of multi-color printing process gamuts, we used the high-quality Pantonecompatible inks produced by the Swiss company SICPA and printed them on coated paper. Colorimetric measurements were carried out using the Gretag SPM100 photospectrometer.
46 citations