Marcel Lucassen - Academia.edu (original) (raw)

Papers by Marcel Lucassen

Conference on Colour in Graphics, Imaging, and Vision, 2004

Conference on Colour in Graphics, Imaging, and Vision, 2002

This paper describes the application of the combined knowledge on colorimetry, colour imaging (vi... more This paper describes the application of the combined knowledge on colorimetry, colour imaging (visualization) and colour perception in an aviation related research project. It involves the optimisation of the conspicuity of the colour scheme of an airplane, with the purpose of minimizing the changes of a mid-air collision. Subjects determined the conspicuity (here defined as object detection in the visual periphery) of different airplane colours at a simulated distance of 1 km and for different simulated atmospheric visibilities. Results indicate that the conspicuity depends on the lightness difference between the airplane and its background, but not on the difference in hue or saturation. Figure 1. Photographs of the Pilatus PC-7. Length and wingspan are about 10 m. The current colour scheme is mainly yellow, red, white and black. When observed from a distance of 1 km, this aircraft subtends a visual angle of 1 degree (about the size of a thumbnail at arm's length).The black "nose" just in front of the cockpit prevents the pilot from being blinded by reflected sunlight.

Conference on Colour in Graphics, Imaging, and Vision, 2010

What happens to color emotion responses when texture is added to color samples? To quantify this ... more What happens to color emotion responses when texture is added to color samples? To quantify this we performed an experiment in which subjects ordered samples (displayed on a computer monitor) along four scales: Warm-Cool, Masculine-Feminine, Hard-Soft and Heavy-Light. Three sample types were used: uniform color, grayscale textures and color textures. Ten subjects arranged 315 samples (105 per sample type) along each of the four scales. After one week, they repeated the full experiment. The effect of adding texture to color samples is that color remains dominant for the Warm-Cool, Heavy-Light and Masculine-Feminine scale (in order of descending dominance), the importance of texture increases in that same order. The Hard-Soft scale is fully dominated by texture. The average intra-observer variability (between the first and second measurement) was 0.73, 0.66 and 0.65 for the uniform color, grayscale texture and color texture samples, respectively. The average inter-observer variability (between an observer and the other observers) was 0.68, 0.77 and 0.65, respectively. Using some 25,000 observer responses, we derived analytical functions for each sample type and emotion scale (except for the Warm-Cool scale on grayscale textures). These functions predict the group-averaged scale responses from the samples' color and texture parameters. For uniform color samples, the accuracy of our functions is significantly higher (average adjusted R 2 = 0.88) than that of functions previously reported. For color texture, the average adjusted R 2 =0.80.

Color Imaging Conference, 1993

Wemeasure the color fidelity of visual scenes that are rendered under different (simulated) illum... more Wemeasure the color fidelity of visual scenes that are rendered under different (simulated) illuminants and shown on a calibrated LCD display. Observers make triad illuminant comparisons involving the renderings from two chromatic test illuminants and one achromatic reference illuminant shown simultaneously. Four chromatic test illuminants are used: two along the daylight locus (yellow and blue), and two perpendicular to it (red and green). The observers select the rendering having the best color fidelity, thereby indirectly judging which of the two test illuminants induces the smallest color differences compared to the reference. Both multicolor test scenes and natural scenes are studied. The multicolor scenes are synthesized and represent ellipsoidal distributions in CIELAB chromaticity space having the same mean chromaticity but different chromatic orientations. We show that, for those distributions, color fidelity is best when the vector of the illuminant change (pointing from n...

Color constancy algorithms are often evaluated by using a distance measure that is based on mathe... more Color constancy algorithms are often evaluated by using a distance measure that is based on mathematical principles, such as the angular error. However, it is unknown whether these distance measures correlate to human vision. Therefore, the main goal of our paper is to analyze the correlation between several performance measures and the quality, obtained by using psychophysical experiments, of the output images generated by various color constancy algorithms. Subsequent issues that are addressed are the distribution of performance measures, suggesting additional and alternative information that can be provided to summarize the performance over a large set of images, and the perceptual significance of obtained improvements, i.e., the improvement that should be obtained before the difference becomes noticeable to a human observer.

Abstract. Color constancy is the ability to measure image features independent of the color of th... more Abstract. Color constancy is the ability to measure image features independent of the color of the scene illuminant and is an important topic in color and computer vision. As many color constancy algorithms exist, different distance measures are used to compute their accuracy. In general, these distances measures are based on mathematical principles such as the angular error and Euclidean distance. However, it is unknown to what extent these distance measures correlate to human vision. Therefore, in this paper, a taxonomy of different distance measures for color constancy algorithms is presented. The main goal is to analyze the correlation between the observed quality of the output images and the different distance measures for illuminant estimates. The output images are the resulting color corrected images using the illuminant estimates of the color constancy algorithms, and the quality of these images is determined by human observers. Distance measures are analyzed how they mimic ...

The parametric factors kL, kC and kH that scale the CIELAB components kL*, kC* and kH* in the CIE... more The parametric factors kL, kC and kH that scale the CIELAB components kL*, kC* and kH* in the CIE94 colour difference formula are unity under reference conditions. When the conditions are changed, the scaling factors may be adapted to account for the influence of specific experimental conditions on perceived colour differences. We determined thresholds for the visibility of static background noise and for the visibility of a test symbol. The noise was present in only one of the L*, C* or H* dimensions, and the test symbol was an increment to the background, also in one of the dimensions L*, C* or H*. In order to maintain a perceptual uniform difference metric between test symbol and noisy background we arrived at kL = 0.15, kC= 0.52, and kH = 2.21, such that a just noticeable difference corresponds to kE*94=1. When the dimension (L*, C* or h*) of the incremental test symbol is the same as that of the noise in the background, the threshold for the test symbol increases linearly with ...

We report on a dynamic simulation of defective color vision. Using an RGB video camera connected ... more We report on a dynamic simulation of defective color vision. Using an RGB video camera connected to a PC or laptop, the captured and displayed RGB colors are translated by our software into modified RGB values that simulate the color appearance of a person with a color deficiency. Usually, the simulation of deficient color vision is restricted to static images and to dichromats (lacking one cone type). We are now able to also simulate color blindness in near real time video, and for both dichromats and anomalous trichromats. We discuss how these techniques were applied in a field study into color vision requirements in Dutch maritime practice and present visualization examples thereof.

The solution to get this book is that we don't over you the free book. But, we offer you the ... more The solution to get this book is that we don't over you the free book. But, we offer you the free information about color in computer vision. Why should be this book to read and where is the place to get it, even the soft file forms are common questions to utter. In this website, we don't only provide this book. We have still lots of books to read. Yeah, we are on-line library that is always full of recommended books.

Given an RGB image of a visual scene presented on a color display, how would the scene look under... more Given an RGB image of a visual scene presented on a color display, how would the scene look under a different illuminant? This question may be encountered in cases where a more or less realistic visualization is required or in psychophysical studies on topics like color constancy. A method is presented (based on existing technology) that does not require knowledge of the spectral reflectance functions of the objects in the scene. It uses the colorimetric calibration of the display to convert RGB values to CIE XYZ tristimulus values, makes an assumption about the illuminant, and applies van Trigt's [1,2] method for calculation of the smoothest reflectance function for each color in the image. The effect of changes in the spectral composition of the illuminant can then be calculated in terms of XYZ, and hence, can be visualized in RGB using the display calibration.

An electronic parts casing which can be easily formed, which allows a reduction in size and which... more An electronic parts casing which can be easily formed, which allows a reduction in size and which resists deformation. The electronic parts casing is composed of a frame member, an inner cover and an outer cover, and is divided into two chambers by a partition provided inside the frame member. On the outer side surfaces of the frame member, there are provided ridges for the engagement of the outer cover, and, in the periphery of the outer cover, there are provided detents to be engaged with the outer ridges of the frame member. On the top surface of the inner cover, there are provided outwardly convex draw surfaces, and, on the top surface of the outer cover, there is provided an outwardly convex draw portion, which has on its inner side an inwardly convex draw surface. The inner cover is placed in contact with the upper edges of the inner cover and of the partition. The convex draw surfaces provided on the inner cover are brought into close contact with the convex draw surface prov...

Journal of Vision

DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

Color and Imaging Conference

Recently, the CIE published a new standard in which the so called 'melanopic daylight efficac... more Recently, the CIE published a new standard in which the so called 'melanopic daylight efficacy ratio' (abbreviated to melanopic DER) is introduced. This number is helpful in estimating the impact that a light source may have on our circadian rhythm. Although the melanopic DER can be directly calculated from the spectral power distribution, in case the latter is unknown a spectrophotometer or similar instrument is required, which is usually unavailable to the general public. Here we demonstrate how the melanopic DER can be accurately estimated from a smartphone image of two selected color samples. In addition, using the smartphone's camera parameters we provide a method to estimate the illuminance. Combined these measurements allow an evaluation of the absolute melanopic stimulation.