In recent years, various methods have been developed for representing, encoding, and controlling colors in digital color-imaging systems. Although many of these methods have been based on the concept of “device-independent” color, none has proven to be completely successful for all systems and applications.This paper will describe a new paradigm for digital color encoding and color management. This single—and deceptively simple—“universal” color-management paradigm encompasses the functionality of all existing colorimaging systems. The paradigm, together with its unique color-encoding method, offers a complete solution to the difficult problem of supporting disparate types of input and output devices and media on a single system. Moreover it fulfills the most fundamental requirement of color management by providing unambiguous and unrestricted communication of color among systems of every kind.The paper will describe how this universal paradigm can be implemented in practice using color transformations consistent with specifications developed by the International Color Consortium (ICC), an industry group formed in 1993 to promote interoperability among color-managed systems. It also will be shown how a color managed system based on the universal paradigm can make optimum use of current interchange metrics, such as the KODAK Photo YCC Color Interchange Space used in the Photo CD System.
We propose a minimax technique to extract the optimum grid structure that will minimize the error in the interpolation of multidimensional functions using sequential linear interpolation (SLI). The error criterion we use is the maximum absolute error. We apply this method to the problem of color printer characterization.
This paper describes a new correction method for the color shift due to the illuminant changes based on the estimation of the spectral reflectance by a neural network. Proposed method has been compared to two conventional methods and evaluated. Our evaluation results show that the method can achieve better accuracy than other methods.
The introduction of ICC-based color management solutions promises a multitude of solutions to graphic arts imaging needs. To those of us who have been involving in the technology of graphic arts imaging, the best way to understand the performance of CMS is to test it. We decided to focus our initial effort on color matching aspects of the ICC profiles.To test the degree of color matching, a number of color patches that are reproduced by a hard copy output device in CIELAB values were specified as aim points. These colors were reproduced by the same output device according to the experimental design which involves three factors: ICC-compliant profiling tool, color rendering style, and work flow. The experimental design yields 8 sets of data. The degree of color matching is judged by average ΔE between the color produced and its original colorimetric specifications. We learned that the accuracy of color matching depends on the work flow, device profiling tools, and color rendering style. An average ΔE of 6.5 represents the best scenario in this particular color matching effort. Other factors such as precision or repeatability of the desktop printer and the measurement instrument which may have contributed differences in color matching were also discussed.
The construction of a system that uses CIE co-ordinate, and reflectance curve specified colour imaging as a colour communication tool is presented. Images are stored and manipulated as object hierarchies, with both an intrinsic object colour, and an object colour-set representing surface detail and texture.
Multispectral image capture (i.e, more than three channels) facilitates both more accurate tristimulus estimation and possibilities for spectral reconstruction of each scene pixel. A seven-channel camera was assembled using approximately 50 nm bandwidth interference filters, manufactured by Melles Griot, in conjunction with a Kodak Professional DCS 200m digital camera. Multichannel images were recorded for the Macbeth ColorChecker chart as an illustrative example. Three methods of spectral reconstruction were evaluated: spline interpolation, modified-discrete-sine-transformation (MDST) interpolation, and an approach based on principal-component analysis (PCA). The spectral reconstruction accuracy was quantified both spectrally and by computing CIELAB coordinates for a single illuminant and observer. The PCA-based technique resulted in the best estimated spectral-reflectance-factor functions. These results were compared with a least-squares colorimetric model that does not include the spectral-reconstruction step. This direct mapping resulted in similar colorimetric performance to the PCA method. The multispectral camera had marked improvement compared with traditional three-channel devices.
A description and analysis of analytical methods to between a digital camera device color space and device independent color spaces under varying lighting conditions will be presented. This approach has been evaluated in the production of an art paintings catalogue.
New quality measures for a set of color sensors—weighted quality factor qe, spectral characteristic restorability index qr and color reproducibility index Q—are proposed to practically evaluate color reproduction quality.Because these quantities take account of object color spectral characteristics, they are more reasonable and useful than previously-proposed quality measures. Simulation results clearly show a good relation between the proposed indices and color reproduction errors after a linear color correction.
Color errors in scanners arise from two sources: the non-colorimetric nature of the scanner sensitivities and the measurement noise. Several measures of goodness have been used to evaluate scanners based on these errors. In this paper, the trustworthiness of these measures is studied through simulations. A new measure incorporating both the above sources of errors and providing excellent agreement with perceived color error is also presented.
The demand for accurate color reproduction has never been as high as it is today. Not only in the high-end electronic prepress market, but also in the desktop publishing and home office markets, the availability of both input and output devices is increasing rapidly.Most of the input devices today capture positive originals: scanners capture either reflective or transmissive originals; digital cameras are capable of capturing real life scenes as well.In some market segments (such as, e.g., the newspaper environment), there also is a definite interest in scanning negative originals. Especially with the new emerging APS standard for film (where manual manipulation of the film strips is no longer necessary), the demand for negative scanning will also increase in the home office market.Scanning negatives, however, is a very delicate process. Not only the input device should be characterised properly, but also the negative film itself is a parameter which needs to be studied carefully. On negative film, the information is stored inverted and due to the color dye layers within the negative film, there also is a density shift between the red, green and blue planes. The main problem, however, is caused by the fact that, due to the variations in the development process, the characteristics of a strip of developed negative film can differ considerably from other strips of the same film type.In this paper, we first give a brief survey of our approach to scanning negatives presented in the past. Then, we show how the unpredictable properties of negative films can cause this approach to fail and discuss some substantial improvements. In this respect, we show how the adaptive approach taken in the conventional photo-finishing environment can be used electronically. In a following section, we describe how the inverted positive image data can be transformed into a well-known, calibrated color space. In the last section, we briefly discuss the minimal requirements for an ideal negative scanner.