Visual experiments, if performed in a traditional way, require asking participants to go to a laboratory, where displays
are calibrated and illumination conditions are set in a convenient way. In recent years there has been an increasing
interest in performing the experiments "out of the lab", with the aim of reducing costs, increasing the number of
participants, and differentiating the population. The equivalence of the response of visual experiments performed in
controlled and uncontrolled contexts is an open question which calls for research. In this work we aim at analyzing
more deeply the equivalence between "controlled" and "uncontrolled" that we found in a previous study of the authors
on the comparison of visual preferences for printed images. In particular, we are interested in understanding if, and to
what degree, the uncontrolled experiments require actually more participants in order to average out the effects of the
many uncontrolled parameters which may affects the response. In addition we aim at exploring the relationship, if any,
between our previous conclusions and the difference in the attributes of the images for which the observers were asked
to express their preference.
Visual experiments, attesting visual preference, visual ranking and visual differentiation, are very important to academia
and industry. They are traditionally performed into laboratories under controlled viewing conditions, resulting very
costly in their execution, due to the time and effort involved by all participants. If controlled tests could be substituted
by uncontrolled tests, a potential serious improvement could be obtained by eliminating a large part of the cost. In this
work we investigate if, and to what extent, visual experiments performed under controlled viewing conditions can be substituted by uncontrolled experiments. A task of visual preference of prints is carried out. This task is performed in the laboratory, under controlled viewing conditions, and in many different places, under natural, artificial and mixed light. We observe statistical equivalence for preferences expressed in controlled or uncontrolled conditions that supports the hypothesis that visual preference can be assessed with uncontrolled tests.
In psychological research, it is common to perform investigations on the World Wide Web in the form of questionnaires to collect data from a large number of participants. By comparison, visual experiments have been mainly performed in the laboratory, where it is possible to use calibrated devices and controlled viewing conditions. Recently, the Web has been exploited also for "uncontrolled" visual experiments, despite the lack of control on image rendering at the client side, assuming that the large number of participants involved in a Web investigation "averages out" the parameters that
the experiments would require to keep fixed if, following a traditional approach, it was performed under controlled
conditions. This paper describes the design and implementation of a Web-based visual experiment management system, which acts as a repository of visual experiment, and is designed with the purpose of facilitating the publishing of online investigations.
A recent trend in psychophysics experiments related to image quality is to perform the experiments on the World Wide
Web with a large number of observers instead of in a laboratory under controlled conditions. This method assumes that
the large number of participants involved in a Web investigation "averages out" the parameters that the experiments
would require to keep fixed in the same experiment performed, following a traditional approach, under controlled
conditions. In this paper we present the results of two experiments we have conducted to assess the minimum value of
color contrast to ensure readability. The first experiment was performed in a controlled environment, the second on the
Web. The result emerging from the statistical data analysis is that the Web experiment yields the same conclusions as
the experiment done in the laboratory.
One of the issues in Web page design is the selection of appropriate combinations of background and foreground colors to display textual information. Colors have to be selected in order to guarantee legibility for different devices, viewing conditions and, more important, for all the users, including those with deficient color vision. In this paper we present a tool to select background and foreground colors for the display of textual information. The tool is based on the Munsell Book of Colors; it allows the browsing of the atlas and indicates plausible colors based on a set of legibility rules, which have been defined experimentally.
The availability of large audio collections calls for ways to efficiently access and explore them by providing an effective overview of their contents at the interface level. In this paper we present an innovative strategy exploiting color to visualize the content of a database of audio records, part of a website dedicated to ethnographic information in a region of Italy.
Spectral characterization involves building a model that relates the device dependent representation to the reflectance function of the printed color, usually represented with a high number of reflectance samples at different wavelengths. Look-up table-based approaches, conventionally employed for colorimetric device characterization cannot be easily scaled to multispectral representations, but methods for the analytical description of devices are required. The article describes an innovative analytical printer model based on the Yule–Nielsen Spectral Neugebauer equation and formulated with a large number of degrees of freedom in order to account for dot-gain, ink interactions, and printer driver operations. To estimate our model's parameters we use genetic algorithms. No assumption is made concerning the sequence of inks during printing, and the printers are treated as RGB devices (the printer-driver operations are included in the model). We have tested our characterization method, which requires only about 130 measurements to train the learning algorithm, on four different inkjet printers, using different kinds of paper and drivers. The test set used for model evaluation was composed of 777 samples, uniformly distributed over the RGB color space.
In many applications, it is requested to compute surface color appearance under different illuminants. If multispectral information about surface reflectance is available, the calculus of tristimulus values under illuminants of specified SPD is straightforward. When only colorimetric information is known, the illuminant change is performed adopting transforms based on the Von Kries scaling model (i.e. the Bradford transform). Unfortunately, the three dimensional colorimetric space may be limited for properly computing the change in appearance of colors due to a change of illuminant. In this paper, a solution to this problem is presented. Assumption of the proposed method is that the problem is specific for a domain of colors, and that this domain can be modeled in a three dimensional Gaussian space. Given the domain Gaussian space, colors may be represented through synthesized reflectance spectra. Exploiting synthesized reflectance is proved to be an effective strategy to implement an illuminant change transform.
The majority of papers illustrating the advantages of multispectral approaches in color imaging consider metamerism reduction as the main reason of turning, in the next years, from colorimetric imaging and reproduction to multispectral. Doubtless, if spectral match is the reproduction criterion, and if this is accomplished with sufficient accuracy, originals and reproductions match, visually, even if viewing conditions change. It follows that, in practical applications, the spectral-based approach is advantageous whenever the viewing conditions are unknown. From a theoretical viewpoint, metamerism-free reproductions have a considerable advantage vis-à-vis traditional prints. In practice, the measurability of such advantage rests on the possibility of a comparison between the original image and the corresponding reproduction, which, in turn, should quantify the ability of the observer to discover the mismatch.
In this work, we compare results of colorimetric and spectral-based reproductions of single color patches in print. We consider a four ink printer, which we characterize colorimetrically and spectrally. Then, we perform a set of experiments. Test colors are reproduced using colorimetric and multispectral strategies. We compare the results obtained through measurements. The aim of our work is to discuss possible advantages or disadvantages of the spectral-based reproduction with respect to colorimetric reproduction for single colors.
Information about the spectral reflectance of a color surface is useful in many applications. Assuming that reflectance functions can be adequately approximated by a linear combination of a small number of basis functions and exploiting genetic algorithms, we address here the problem of synthesizing a spectral reflectance function, given the standard CIE 1931 tristimulus values. Different sets of basis functions have been experimented and different data sets have been used for benchmarking.
In recent years, many methods have been proposed for the spectral-based characterization of inkjet printers. To our knowledge, the majority of these are based on a physical description of the printing process, employing different strategies to deal with mechanical dot gain and the physical interaction among inks. But our experience tells us that as printing is a physical process involving a large number of effects and unpredictable interactions, it is not unusual to be unable to fit a mathematical model to a given printer. The question becomes, therefore, whether it is feasible, and to what degree, to employ an analytical printer model even if it appears to be incapable of describing the behavior of a given device. A key objective of our work is to obtain a procedure that can spectrally characterize any printer, regardless of the paper and the printer driver used. We consider in fact the printers RGB devices, and incorporate the printer driver operations, even if they are unknown to us, into the analytical model.
We report here our experimentation on the use of genetic algorithms to tune a spectral printer model based on the Yule-Nielsen modified Neugebauer equation. In our experiments we have considered three different inkjet printers and used different kinds of paper and printer drivers. For each device the printer model has been tuned, using a genetic algorithm, on a data set of some 150 measured reflectance spectra. The test set was composed of 777 samples, uniformly distributed in the RGB color space.
The paper presents an innovative approach to the spectral-based characterization of ink-jet color printers. Our objective was to design a color separation procedure based on a spectral model of the printer, managed here as an RGB device. The printer was a four-ink device, and we assumed that the driver always replaced the black completely when converting from RGB to CMYK amounts of ink. The color separation procedure, which estimates the RGB values given a reflectance spectrum, is based on the inversion of the Yule-Nielsen modified Neugebauer model. To improve the performance of the direct Neugebauer model in computing the reflectance spectrum of the print, given the amounts of ink, we designed a method that exploits the results of the numerical inversion of the Neugebauer model to estimate a correction of the amount of black ink computed on RGB values. This correction can be considered a first step in optimization of the Neugebauer model; it accounts for ink-trapping and the lack of knowledge on how the black is actually replaced by the printer driver.
We have examined the performance of various color-based retrieval strategies when coupled with a pre-filtering Retinex algorithm to see whether, and to what degree, Retinex improved the effectiveness of the retrieval, regardless of the strategy adopted. The retrieval strategies implemented included color and spatial-chromatic histogram matching, color coherence vector matching, and the weighted sum of the absolute differences between the first three moments of each color channel. The experimental results are reported and discussed.
Proc. SPIE. 4300, Color Imaging: Device-Independent Color, Color Hardcopy, and Graphic Arts VI
KEYWORDS: Human-machine interfaces, Visualization, Vegetation, Data visualization, Human vision and color perception, Chemical elements, Algorithm development, Space operations, Graphic design, Information visualization
In this paper, we describe the main feature of a system supporting the selection of color palettes for qualitative data representation and graphic interface design. The system is mainly based on visual interaction providing effective tools for browsing the Munsell color space and setting perceptual constraints on the number and type of colors the system selects automatically. The system can also manage ICC device profiles, making it possible to process colors in terms of standard, device-independent color representation. Experimental results are also reported.
This paper present the results of the activities concerning the architecture of a high quality catalogue for made-to- measure garments undertaken in the ISHTAR project. The syste is based upon servers and standard Internet browsers. The main issues faced in this paper are the definition of an architecture to obtain the best trade off between performance and representation of apparel/textile goods and the introduction of a color management system that can benefit also generic internet users.