Adjacent Color Research Articles

Absolute Color Scale for Improved Diagnostics with Wavefront Error Mapping

Wavefront data are expressed in micrometers and referenced to the pupil plane, but current methods to map wavefront error lack standardization. Many use normalized or floating scales that may confuse the user by generating ambiguous, noisy, or varying information. An absolute scale that combines consistent clinical information with statistical relevance is needed for wavefront error mapping. The color contours should correspond better to current corneal topography standards to improve clinical interpretation. Retrospective analysis of wavefront error data. Historic ophthalmic medical records. Topographic modeling system topographical examinations of 120 corneas across 12 categories were used. Corneal wavefront error data in micrometers from each topography map were extracted at 8 Zernike polynomial orders and for 3 pupil diameters expressed in millimeters (3, 5, and 7 mm). Both total aberrations (orders 2 through 8) and higher-order aberrations (orders 3 through 8) were expressed in the form of frequency histograms to determine the working range of the scale across all categories. The standard deviation of the mean error of normal corneas determined the map contour resolution. Map colors were based on corneal topography color standards and on the ability to distinguish adjacent color contours through contrast. Higher-order and total wavefront error contour maps for different corneal conditions. An absolute color scale was produced that encompassed a range of +/-6.5 microm and a contour interval of 0.5 microm. All aberrations in the categorical database were plotted with no loss of clinical information necessary for classification. In the few instances where mapped information was beyond the range of the scale, the type and severity of aberration remained legible. When wavefront data are expressed in micrometers, this absolute scale facilitates the determination of the severity of aberrations present compared with a floating scale, particularly for distinguishing normal from abnormal levels of wavefront error. The new color palette makes it easier to identify disorders. The corneal mapping method can be extended to mapping whole eye wavefront errors. When refraction data are expressed in diopters, the previously published corneal topography scale is suggested.

Some new bounds on [formula omitted]-choosability

List T-colouring is a generalisation of list colouring in which the differences between adjacent colours must not lie in the set T. We present a conjecture giving an upper bound on the T r -choosability T r - ch ( G ) (where T r = { 0 , 1 , … , r } ) in terms of r and ch ( G ) which, if true, is tight for all values of r and ch ( G ) , and we prove the bound in the case ch ( G ) = 2 . We also prove the conjecture with the colouring number col ( G ) in place of ch ( G ) , and use this result in conjunction with a theorem of Alon to establish an exponential upper bound on T r - ch ( G ) in terms of r and ch ( G ) .

Variant and invariant color perception in the near peripheral retina

Perceived shifts in hue that occur with increasing retinal eccentricity were measured by using an asymmetric color matching paradigm for a range of chromatic stimuli. Across nine observers a consistent pattern of hue shift was found; certain hues underwent large perceived shifts in appearance with increasing eccentricity, while for others little or no perceived shift was measured. In separate color naming experiments, red, blue, and yellow unique hues were found to be correlated with those hues that exhibited little or no perceptual shift with retinal eccentricity. Unique green, however, did not exhibit such a strong correlation. Hues that exhibited the largest perceptual shifts in the peripheral retina were found to correlate with intermediate hues that were equally likely to be identified by adjacent color naming mechanisms. However, once again the correlation was found to be weakest for the green mechanism. These data raise the possibility that perceptually unique hues are linked to color signals that represent the most reliable (minimally variant) chromatic information coming from the retina.

Full Color Theorems for L(2,1)-Colorings

The span $\lambda$ (G) of a graph G is the smallest k for which G's vertices can be L(2,1)-colored, i.e., colored with integers in $\{0,1, \ldots, k \}$ so that adjacent vertices' colors differ by at least 2, and colors of vertices at distance two differ. G is full-colorable if some such coloring uses all colors in $\{0,1, \ldots, \lambda (G) \}$ and no others. We prove that all trees except stars are full-colorable. The connected graph G with the smallest number of vertices exceeding $\lambda$ (G) which is not full-colorable is C6. We describe an array of other connected graphs that are not full-colorable and go into detail on full-colorability of graphs of maximum degree four or less.

Multifractal structure in nonrepresentational art

Multifractal analysis techniques are applied to patterns in several abstract expressionist artworks, painted by various artists. The analysis is carried out on two distinct types of structures: the physical patterns formed by a specific color ("blobs") and patterns formed by the luminance gradient between adjacent colors ("edges"). It is found that the multifractal analysis method applied to "blobs" cannot distinguish between artists of the same movement, yielding a multifractal spectrum of dimensions between about 1.5 and 1.8. The method can distinguish between different types of images, however, as demonstrated by studying a radically different type of art. The data suggest that the "edge" method can distinguish between artists in the same movement and is proposed to represent a toy model of visual discrimination. A "fractal reconstruction" analysis technique is also applied to the images in order to determine whether or not a specific signature can be extracted which might serve as a type of fingerprint for the movement.

Common Region and Spatial Performance Using Map-Like Displays

Three techniques of perceptual grouping were compared in terms of their effect on people's ability to read maps that always remained visible. The techniques differ in the way they create clusters of objects on map-like displays: by using boundary lines to form adjacent “countries” (Common Region), by coloring “city” symbols that belong to the same, contiguous, country in a unique way (Adjacent Color), or by using color to create spatially non-contiguous, overlapping, clusters (Color Only). Subjects were asked to compare the horizontal orientations of two cities at a time, and, in another task, to compare two distances corresponding to three map cities. Results show that orientation statements were verified faster for same-cluster cities than for differentcluster cities, but only in the Common Region condition. Neither distance estimations nor orientation judgments were distorted by any grouping technique, as indicated by an effect on judgment accuracy. The implications of these results for our understanding of map reading ability in relation to techniques for perceptual grouping are discussed.

Spatial processing in color reproduction

We consider the reproduction of color subject to material and neighborhood constraints. By "material constraints," we mean any constraints that are applied to the amount of ink, lights, voltages, and currents that are used in the generation of color. In the first instance we consider the problem of reproducing a target color constrained by maximum additive color signals, such as in the phosphorescence process in a cathode ray tube. In the second instance we consider the more difficult problem of reproducing color subject to constraints on the maximum primary color variations in a (spatial) neighborhood. We introduce the idea of adjacent color variance (ACV) and then attempt to reproduce colors subject to an upper bound on the ACV. An algorithm that is suitable for this task is the method of vector space projections (VSP). In order to use VSP for constrained color reproduction, we use a novel approach to linearize nonlinear CIE-Lab space constraints. Experimental results are furnished that demonstrate that using the ACV as a bound helps to reduce reproduction artifacts in a color image.

Extraction of Road Traffic Signs using Similarity of Adjacent Color Information

Extraction of Road Traffic Signs using Similarity of Adjacent Color Information

Removing Eyebrows Impairs Recognition of Famous Faces, or Doesn't, Depending on How the Eyebrows are Removed

Matching photos of famous people's faces with their names was as fast with photos that had eyebrows masked by adhesive plaster as with unretouched original photos. But matching was slower with photos that had eyebrows erased and replaced with adjacent skin texture and colour than with original photos. The conjecture that erasure impairs recognition because it alters a face's configuration was examined by repeating the experiment with the photos shown upside down, the rationale being that because configural information is difficult to encode from inverted faces the erasure effect should diminish. With inverted faces, matching was no different for original, eyebrows-masked, and eyebrows-erased photos. Eyebrows appear to be less important for face recognition as informative parts and features than as sources of information about a face's configuration.

Color image quantization using distances between adjacent colors along the color axis with highest color variance

This paper describes a simple but effective hierarchically divisive colormap design technique for color image quantization. By sorting colors based on their components along the principal axis, the one with the highest variance of color distribution, the Euclidean distances between any adjacent colors' along the axis are used to find the cutting plane that is perpendicular to the axis and divides a color cell into two subcells with approximately equal quantization errors with respect to their centroids. As a result, the total quantization error on both cells is minimal. The experimental results reveal that the proposed algorithm is effective and yields a better execution time when compared with others. Moreover the proposed method performs well on both pictures with 15-bit and 24-bit colors regardless of a number of colors in the colormap.

Extraction of Road Traffic Signs using Similarity of Adjacent Color Information(Vision and Recognition 1,Session: MA1-D)

Extraction of Road Traffic Signs using Similarity of Adjacent Color Information(Vision and Recognition 1,Session: MA1-D)

The development of conceptual colour categories in pre-school children: Influence of perceptual categorization

This study investigates the influence of perceptual colour categorization on the development of conceptual colour space in 43 pre-school children as a function of language-age. Knowledge of the 11 basic colour terms identified by Berlin and Kay (1969) was assessed in comprehension and naming tasks. Children's ability to comprehend basic colour terms was assessed in a spoken word-to-colour matching task in which a target colour was presented with two distracters from either distant or adjacent perceptual colour categories. Children's ability to name basic colour sensations was measured in an explicit naming task. Results showed that children's comprehension of basic colour terms was influenced by the perceptual relationship between the target and distracter colours. Most importantly, at a language-age of 3 years and above, naming errors were more likely to be made to adjacent, rather than distant, perceptual colour categories. These results are consistent with the prediction that categorical colour perception influences the underlying structure of developing conceptual colour space during the period in which children acquire basic colour terms.

Cotton Color Classification by Fuzzy Logic

This paper describes the application of fuzzy logic to cotton color grading in an attempt to improve the acceptance of machine grading for cotton colors. Cotton color grades are a number of classes in the (Rd, b) color space. Adjacent color classes have blurry and overlapping boundaries, making crisp-boundary methods ineffective for cotton color classification. Fuzzy logic is specialized to deal with uncertainty and imprecision in the decision-making process, and thus offers a new approach for grading cotton colors. In this paper, we present the procedures for constructing a fuzzy inference system (FIS) using fuzzy logic to classify major classes of cotton colors, and the preliminary results to demonstrate FIS effectiveness in reducing machine-classer disagreements in color grading. The results from the Fis show great consistency for multiple year of cotton color data.

A Coloring Problem With Restrictions of Adjacent Colors

The coloring problem is a well‐known problem of graphs. This paper considers a new coloring problem with restrictions such that some pairs of colors cannot be used for adjacent vertices, called coloring problem with restrictions of adjacent colors. The restriction of adjacent colors can be represented by a graph H called a restriction graph, i.e., each vertex represents a color and each edge means that the two colors corresponding to the two end‐vertices of the edge cannot be used for adjacent vertices. This paper shows some properties of the new coloring problem. It also presents a necessary and sufficient condition such that a restriction graph H cannot be replaced with a more simple graph, when H is a cactus with no 3‐cycle.

A Spectral Reflectance Measuring System which Corrects for Lateral Diffusion Error and Effects of Adjacent Surface Colors

Lateral diffusion error (LDE) is defined and the conventional methods of instrument configuration which minimize it are discussed. In 1999 it was discovered that the amount of light that laterally diffuses from an illuminated sample area to the adjacent unilluminated area is related to the spatial distribution of the light reflected by the illuminated area of the sample. A breadboard spectro-reflectometer which makes use of this relationship to correct for LDE has been built and test results are reported. Papers presented at the 2000 & 2001 TAGA meeting reported that printed colored areas adjacent to an unprinted area can affect the measured spectral reflectance value. This problem was attributed to bilateral diffusion of light between the area being measured and the adjacent printed colored area. The breadboard instrument was tested to determine if its capability to correct for LDE would result in correction of errors due to adjacent colors.

Use of an automated fluorescent microsphere method to measure regional blood flow in the fetal lamb

We have developed a method for measuring regional blood flow by means of fluorescent microspheres in all organs and tissues of the fetal lamb, including brain, heart, lung, liver, gut, spleen, kidney, adrenal, brown fat, skin, muscle, bone, and placenta. Five different fluorescent-labeled microspheres were used: blue (B), yellow-green (Y), orange (O), red (R), and crimson (C). An automated, 96-well microplate fluorescent reader (bottom reading) was chosen for the assay because of the rapidity and high throughput that it offers. Tissue samples were digested by 4 M ethanolic KOH. The sedimentation method and dye extraction with Cellosolve acetate, as previously reported by others, were used for the sample processing. The bones were crushed and allowed to directly soak in Cellosolve acetate to extract the dye. The relationship between microsphere number and fluorescent intensity was linear over a broad range of microsphere numbers (80-20,000/mL). The coefficients of variation of within-run and between-run precision were 3.39 +/- 1.10% and 4.54 +/- 1.10%, respectively. Recovery of microspheres from tissues and blood averaged 94.3 +/- 2.5% and was not dependent on microsphere number. The spillover of the fluorescent signals into adjacent colors was 4.0 +/- 0.1% for O to Y, 8.1 +/- 0.4% for O to R, and 9.1 +/- 0.5% for R to C, and these values were constant over a wide range in concentrations of the microsphere pairs. No evidence was obtained for quenching of the emission of one fluorophore via photon absorption by another fluorophore. The measurements of regional blood flow obtained with fluorescent microspheres in three chronically instrumented fetal lambs at approximately 140 days gestation were similar to the flow estimates obtained using radioactive microspheres in four other fetal lambs at the same gestational age. The fluorescent method is thus a viable alternative to the radioactive technique for the measurement of regional blood flow to all fetal organs and tissues, particularly when an automated fluorescent microplate reader is employed to reduce analysis time.

Use of an automated fluorescent microsphere method to measure regional blood flow in the fetal lamb

We have developed a method for measuring regional blood flow by means of fluorescent microspheres in all organs and tissues of the fetal lamb, including brain, heart, lung, liver, gut, spleen, kidney, adrenal, brown fat, skin, muscle, bone, and placenta. Five different fluorescent-labeled microspheres were used: blue (B), yellow-green (Y), orange (O), red (R), and crimson (C). An automated, 96-well microplate fluorescent reader (bottom reading) was chosen for the assay because of the rapidity and high throughput that it offers. Tissue samples were digested by 4 M ethanolic KOH. The sedimentation method and dye extraction with Cellosolve acetate, as previously reported by others, were used for the sample processing. The bones were crushed and allowed to directly soak in Cellosolve acetate to extract the dye. The relationship between microsphere number and fluorescent intensity was linear over a broad range of microsphere numbers (80-20,000/mL). The coefficients of variation of within-run and between-run precision were 3.39 +/- 1.10% and 4.54 +/- 1.10%, respectively. Recovery of microspheres from tissues and blood averaged 94.3 +/- 2.5% and was not dependent on microsphere number. The spillover of the fluorescent signals into adjacent colors was 4.0 +/- 0.1% for O to Y, 8.1 +/- 0.4% for O to R, and 9.1 +/- 0.5% for R to C, and these values were constant over a wide range in concentrations of the microsphere pairs. No evidence was obtained for quenching of the emission of one fluorophore via photon absorption by another fluorophore. The measurements of regional blood flow obtained with fluorescent microspheres in three chronically instrumented fetal lambs at approximately 140 days gestation were similar to the flow estimates obtained using radioactive microspheres in four other fetal lambs at the same gestational age. The fluorescent method is thus a viable alternative to the radioactive technique for the measurement of regional blood flow to all fetal organs and tissues, particularly when an automated fluorescent microplate reader is employed to reduce analysis time.

Multicentre evaluation of the urine analyser Miditronr` Junior

A multicentre evaluation of the urine analyser Miditronr` Junior was performed at four laboratories. The Miditronr` Junior analyser provides semi-quantitative results for erythrocytes, bilirubin, urobilinogen, ketone bodies, glucose, protein, nitrite, leukocytes, pH and relative density. Accuracy of the Miditronr` Junior analyser was evaluated by comparison to quantitative analytical chemistry methods (glucose, total protein), physical methods (pH, relative density), and microscopic methods (erythrocytes, leukocytes). Agreement was defined as identical or neighbouring concentration block. The level of agreement found with chemical, physical or microscopic methods for the six analytes tested varied from 79 to 99%. The within-run precision was determined as repeatability by using 31 native urines. The results of repeated measurements (n=10) fell in the same concentration block, or in case of borderline concentration were spaced between two adjacent colour blocks. Day-to-day precision covering a minimum of 20 days using commercially available control solutions yielded results within ± one colour block from the mean.

Graph homomorphisms with infinite targets

Let H be a fixed graph whose vertices are called colours. Informally, an H -colouring of a graph G is an assignment of these colours to the vertices of G such that adjacent vertices receive adjacent colours. We introduce a new tool for proving NP-completeness of H -colouring problems, which unifies all methods used previously. As an application we extend, to infinite graphs of bounded degree, the theorem of Hell and Nešetřil that classifies finite H -colouring problems by complexity.

Seeing depth in colour: More than just what meets the eyes

Novel binocular depth illusions obtained from two-dimensional colour images are presented. It is demonstrated that the magnitude of these illusions is based on transverse chromatic aberation (TCA), however, the depth obtained cannot be observed unless specific conditions are met even if the TCA is present. Some form of perceptual organization occurring at and/or beyond the binocular fusion site of the brain, is required for some of these effects to occur. An example of a paradoxical finding leading to this conclusion is the observation that under some conditions the same colour can be perceived on separate depth planes while spatially adjacent colours from opposing ends of the visible spectrum (i.e. red and blue or green) can be perceived on the same depth plane simultaneously within the same image. Further, results show that some form of reference plane is required by the brain to use the colour induced disparity, without which, depth cannot be perceived even if the disparity information is present. This phenomenon is spatially tuned for medium to high frequency components and is still detectable under isoluminant conditions which would support the notion that it requires information from the parvocellular pathway. Binocular lustre and rivaldepth are ruled out as being significant factors in the effect. It is argued that this phenomenon represents an instance of global interactive processes induced by TCA while previous studies on chromostereopsis have concentrated on local aspects. Results of the present study may explain why under certain situations depth can be perceived in coloured images and not under other circumstances where TCA is still present.