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.
Citations
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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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TL;DR: In this article, the authors consider both image independent and image dependent quantizers implemented in RGB or in the uniform color space L *u*υ*, and the halftoning techniques that they use are multilevel extensions of error diffusion and ordered dither.
Abstract: Algorithms are investigated for the printing or display of color images at near-original image quality with a minimum number of output colors. Each algorithm consists of a quantizer that is used possibly in conjunction with halftoning. We consider both image-independent and image-dependent quantizers implemented in RGB or in the uniform color space L*u*υ*. The halftoning techniques that we use are multilevel extensions of error diffusion and ordered dither. Image quality resulting from the use of these algorithms is measured by subjective evaluation.
61 citations
IBM1
TL;DR: A halftoning algorithm is presented in which novel concepts are combined resulting in an output image in which moire patterns are suppressed and, at the same time, the edges are enhanced.
Abstract: Most printers and some display devices are bilevel (black or white) and therefore not capable of reproducing continuous tone pictures. Digital halftoning algorithms transform digital gray scale images into bilevel ones which give the appearance of containing various shades of gray. A halftoning algorithm is presented in which novel concepts are combined resulting in an output image in which moire patterns are suppressed and, at the same time, the edges are enhanced. Various other artifacts associated with the halftoning process, such as contouring due to coarse quantization or to textural changes, are also absent from the output images in the proposed scheme. The algorithm separates the image into many small clusters which are processed independently and, therefore, it is capable of parallel implementation.
57 citations
TL;DR: Experimental results show that the modified methods, especially the method using the LAB color space, resulted in better color reproduction performance than the conventional methods and achieves a good spatial image quality.
Abstract: Taking colorimetric color reproduction into account, the conventional error diffusion method is modified for color digital half-toning. Assuming that the input to a bilevel color printer is given in CIE-XYZ tristimulus values or CIE-LAB values instead of the more conventional RGB or YMC values, two modified versions based on vector operation in (1) the XYZ color space and (2) the LAB color space were tested. Experimental results show that the modified methods, especially the method using the LAB color space, resulted in better color reproduction performance than the conventional methods. Spatial artifacts that appear in the modified methods are presented and analyzed. It is also shown that the modified method
(2) with a thresholding technique achieves a good spatial image quality.
56 citations
TL;DR: This work proposes a method for designing an optimized universal color palette for use with halftoning methods such as error diffusion, and employs a new vector quantization method known as sequential scalar quantization (SSQ) to allocate the colors in a visually uniform color space.
Abstract: Currently, many low-cost computers can only simultaneously display a palette of 256 colors. However, this palette is usually selectable from a very large gamut of available colors. For many applications, this limited palette size imposes a significant constraint on the achievable image quality. We propose a method for designing an optimized universal color palette for use with halftoning methods such as error diffusion. The advantage of a universal color palette is that it is fixed and therefore allows multiple images to be displayed simultaneously. To design the palette, we employ a new vector quantization method known as sequential scalar quantization (SSQ) to allocate the colors in a visually uniform color space. The SSQ
method achieves near-optimal allocation, but may be efficiently implemented using a series of lookup tables. When used with error diffusion, SSQ adds little computational overhead and may be used
to minimize the visual error in an opponent color coordinate system. We compare the performance of the optimized algorithm to standard error diffusion by evaluating a visually weighted mean-squared-error measure. Our metric is based on the color difference in CIE L *a *b , but also accounts for the lowpass characteristic of human contrast sensitivity.
54 citations
TL;DR: The Munsell Color Science Laboratory model and visual colorimeter for collecting color-matching-function data have demonstrated results that correlate well with data collected using the National Research Council of Canada's Trichromator.
Abstract: The Munsell Color Science Laboratory model and visual colorimeter for collecting color-matching-function data were described in Part I of this article. The model and instrument have demonstrated results that correlate well with data collected using the National Research Council of Canada's Trichromator. Color-matching-function data for 18 observers and 20 repetitions on a single observer have been obtained using the Munsell Color Science Laboratory visual colorimeter. The variability for the single observer for 20 repetitions over a month's time was found to be similar to the uncertainty of matching within a single measurement session. The variability of the 18 observers was found to be much larger. The results were compared with the CIE Standard Deviate Observer. The variability of the CIE Standard Deviate Observer was on the order of the single observer variability while the multiple observer variability was significantly larger.
53 citations