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In this paper, the effect of the protan recoloring algorithm on an image with an inserted watermarkis analyzed. In addition, the effect of degradation of the quality of the recolored image due to the insertion ofwatermarks and superimposed AWGN was also analyzed. In the first part of the paper, the effect of color visiondeficiency, as a consequence of anomalies in L cones, which is designated as protanomaly (protanopia), isdescribed. People with protanopia do not see a wide range of colors because the colors from the L channel aremissing. After that, the recoloring algorithm, which performs recoloring of the image, so that, in protan persons,the visible spectrum of colors is expanded, is described. Then, the algorithm for inserting a watermark, in orderto protect copyrights, is described. In the second part of the work, the Experiment, in which the quality of therecoloring image was tested, as well as the quality of the extracted watermark, was described. The results of theexperiment are shown with pictures and tables. By applying a comparative analysis of the results of theexperiment, using objective (MSE, PSNR, NC and SSIM) and subjective (visual inspection) methods, theinsertion factor of the watermark, α, which preserves the quality of the recoloring image as well as the quality ofthe extracted watermark, was determined. Visual inspection determined the SNR at which visible imagedegradation and watermarks occur.

This thesis employs a close reading of archival and published sources to explore the origins of colour vision science in 19th century Britain. By drawing attention to wide ranging dialogues and disagreements between diverse figures with different visions of colour, including physicists David Brewster, James Clerk Maxwell, and Lord Rayleigh, politician and philologist William Gladstone, ophthalmologists Frederick Edridge-Green and Robert Carter, and anthropologist W.H.R Rivers, I show that 19th century colour vision science was not narrowly confined to the quantification, measurement, and classification of colours. It was instead shaped by deeper metaphysical questions and wider political concerns. These questions and concerns included the implications of natural law, free-will, and materialism for scientific understandings of reality, the limits of Darwinian understandings of humanity, the legitimacy of scientific experts and institutions in determining public policy, and the history, future, and advancement of civilization. I argue that the widespread use of spinning discs as an experimental research technology, promoted by Brewster and Maxwell, combined with the mainstream acceptance of Maxwell’s theoretical model of ‘coterminal response curves’, generated conflicts between competing understandings of perception, vision, and colour in the second half of the 19th century. These conflicts stemmed from the establishment of new conventions, inspired by Maxwell’s work, which held that scientists should maintain a practical and analytical distance from their own visual experiences, that the visual experiences of test subjects should be treated as untrustworthy phenomena in need of further analysis, and that the meaning of subjective experiences are contained within, and revealed by, mathematical models that accord with a rational understanding of the physical world. These practical and metaphysical approaches to the meaning of human experience did not end with the conflicts they generated in the second half of the 19th century but continue to bear on broader contemporary understandings of truth and illusion in scientific practice and popular imagination., Cambridge Trust

In anomalous trichromacy, the color signals available from comparing the activities of the two classes of cone sensitive in the medium and long wavelength parts of the spectrum are much reduced from those available in normal trichromacy, and color discrimination thresholds along the red-green axis are correspondingly elevated. Yet there is evidence that suprathreshold color perception is relatively preserved; this has led to the suggestion that anomalous trichromats post-receptorally amplify their impoverished red-green signals. To test this idea, we measured chromatic discrimination from white and from saturated red and green pedestals. If there is no post-receptoral compensation, the anomalous trichromat's loss of chromatic contrast will apply equally to the pedestal and to the test color. Coupled with a compressively nonlinear neural representation of saturation, this means that a given pedestal contrast will cause a smaller than normal modulation of discrimination sensitivity. We examined cases where chromatic pedestals impair the color discrimination of normal trichromatic observers. As predicted, anomalous observers experienced less impairment than normal trichromats, though they remained less sensitive than normal trichromats. Although the effectiveness of chromatic pedestals in impairing color discrimination was less for anomalous than for normal trichromats, the chromatic pedestals were more effective for anomalous observers than would be expected if the anomalous post-receptoral visual system were the same as in normal trichromacy; the hypothesis of zero compensation can be rejected. This might suggest that the effective contrast of the pedestal is post-receptorally amplified. But on closer analysis, the results do not support candidate simple models involving post-receptoral compensation either.

Anomalous trichromacy is a form of color vision deficiency characterized by the presence of three cone types, but with shifted spectral sensitivities for L or M cones, causing a red-green color deficiency. However, long-term adaptation to this impoverished opponent input may allow for a more normal color experience at the suprathreshold level (“compensation”). Recent experimental evidence points to the presence of compensation in some tasks. The current study used threshold detection, suprathreshold contrast matching, and a reaction-time task to compare contrast coding in normal and anomalous observers along the cardinal cone-opponent axes. Compared to color normals, anomals required more L-M contrast, but not S contrast, to detect stimuli and to match an achromatic reference stimulus. Reaction times were measured for several contrast levels along the two cone-opponent axes. Anomals had higher overall reaction times, but their reaction-time versus contrast functions could be matched to those of controls simply by scaling contrast by the detection thresholds. Anomalous participants were impaired relative to controls for L-M stimuli in all three tasks. However, the contrast losses were three times greater for thresholds and reaction times than for suprathreshold matches. These data provide evidence for compensation in anomalous trichromats, but highlight the role that the experimental task plays in revealing it.

Anomalous trichromats have three classes of cone receptors but with smaller separation in the spectral sensitivities of their longer-wave (L or M) cones compared to normal trichromats. As a result, the differences in the responses of the longer-wave cones are smaller, resulting in a weaker input to opponent mechanisms that compare the LvsM responses. Despite this, previous studies have found that their color percepts are more similar to normal trichromats than the smaller LvsM differences predict, suggesting that post-receptoral processes might amplify their responses to compensate for the weaker opponent inputs. We evaluated the degree and form of compensation using a hue-scaling task, in which the appearance of different hues is described by the perceived proportions of red-green or blue-yellow primary colors. The scaling functions were modeled to estimate the relative salience of the red-green to blue-yellow components. The red-green amplitudes of the 10 anomalous observers were 1.5 times weaker than for a group of 26 normal controls. However, their relative sensitivity at threshold for detecting LvsM chromatic contrast was on average 6 times higher, consistent with a 4-fold gain in the suprathreshold hue-scaling responses. Within-observer variability in the settings was similar for the two groups, suggesting that the suprathreshold gain did not similarly amplify the noise, at least for the dimension of hue. While the compensation was pronounced it was nevertheless partial, and anomalous observers differed systematically from the controls in the shapes of the hue-scaling functions and the corresponding loci of their color categories. Factor analyses further revealed different patterns of individual differences between the groups. We discuss the implications of these results for understanding both the processes of compensation for a color deficiency and the limits of these processes.

Introduction Classification of color deficiency has required substantial time and expense with the static Farnsworth-Munsell and Innova Rabin tests. Therefore, dynamic color tests were developed for the Nintendo 3DS. Methods Fifteen color deficient patients and 17 age-matched normals performed Rabin color test in addition to PDI Check dynamic color games resembling Farnsworth-Munsell presentation (version 0.2.8) and 3-color iso-luminance gray (version 0.2.13). Results Tests of red, green and blue cone-deficient with the v0.2.8 had sensitivity/specificity/PPV of 92%/86%/92% protanopes, 78%/90%/88% deutanopes and 87%/50%/93% tritanopes. Version 0.2.13 had sens/spec/PPV of 78%/83%/78% red-cone, 100%/85%/80% green cone and 67%/78%/33% blue cone. Corresponding IntraClass Correlation (ICC) utilizing v0.2.8 were red-cone 0.22 (−0.02–0.60), green-cone 0.34 (−0.10–0.67) and blue-cone 0.38 (0.12–0.75). ICC for v0.2.13 was higher with protanope 0.62 (−0.07–0.87), deuteranope 0.64 (−0.09–0.88) and tritanope 0.31 (−0.07–0.70). The PDI Check color game took 65 seconds compared to 197 seconds for Innova Rabin. Conclusion The PDI Check color game quickly identifies patients with inherited color deficiencies., Video Abstract Point your SmartPhone at the code above. If you have a QR code reader the video abstract will appear. Or use: https://youtu.be/oREQZvZ7rpc

The clustering of neurons with similar response properties is a conspicuous feature of neocortex. In primary visual cortex (V1), maps of several properties like orientation preference are well described, but the functional architecture of color, central to visual perception in trichromatic primates, is not. Here we used two-photon calcium imaging in macaques to examine the fine structure of chromatic representation and found that neurons responsive to spatially uniform, chromatic stimuli form unambiguous clusters that coincide with blobs. Further, these responsive groups have marked substructure, segregating into smaller ensembles or micromaps with distinct chromatic signatures that appear columnar in upper layer 2/3. Spatially structured chromatic stimuli revealed maps built on the same micromap framework but with larger subdomains that go well beyond blobs. We conclude that V1 has an architecture for color representation that switches between blobs and a combined blob/interblob system based on the spatial content of the visual scene., Stimulus feature maps are found in primary visual cortex of many species. Here the authors show color maps in trichromatic primates containing segregated ensembles of neurons with distinct chromatic signatures that associate with cortical modules known as blobs.

Although trichromatic colour vision has been extensively studied as it grants significant advantages for Old World primates, it is unknown which selective pressures were behind the trait’s evolution. The leading hypothesis would be that colour vision arose as a foraging adaptation because it allowed individuals to spot food more efficiently. To test this, we exposed 3 chimpanzees (Pan troglodytes), 5 gorillas (Gorilla gorilla) and 3 mandrills (Mandrillus sphinx) to colour cardboard plates to assess whether colours related to diet were the most preferred. The experimental setting was divided into two phases. During the first, animals were provided with colour cardboard plates of only 1 colour per data collection session. The order of colour presentation was randomly determined: white, black, yellow, green and red. In phase 2, primates were simultaneously provided with cardboard plates of all colours. Behavioural interactions with plates were measured using a one-zero group focal sampling (10-s sampling intervals and 20-min observation periods). Results showed that when animals were exposed to only 1 colour at a time, they exhibited different colour preferences depending on the species considered. Chimpanzees preferred red and yellow, the colours linked to fruits, while gorillas selected red and white. Mandrills exhibited fewer differences between colour preferences, with red being the most selected. Furthermore, when all colours were simultaneously provided, individuals chose colours related to diet over black and white. Although there were clear individual differences, our results support that trichromatic colour vision is an advantage in detecting and selecting red items. In the wild, it could be important in the detection of reddish fruits and leaves.

In Moscow in the 1950′s, the physicist M. M. Bongard developed the use of silent substitution to establish the number of dimensions of human or animal colour vision and to derive colour-matching functions either for whole organisms or for individual neuronal channels. In 1956, he and his colleague M. S. Smirnov reported that extra-foveal human vision was tetrachromatic when tested by the silent-substitution method that they called ‘replacement colorimetry’. In the steady state, trichromatic matches were possible in extra-foveal regions, but transients were visible when one such match was replaced by another. If, however, a match was made with four primaries, then a silent substitution was possible; and such matches – unlike trichromatic ones – were stable with light level and with changes in the state of chromatic adaptation. Bongard and Smirnov believed that the fourth receptor had the spectral sensitivity of the rods, but of course they were working long before the discovery of intrinsically photosensitive retinal ganglion cells. On the fiftieth anniversary of Bongard’s grievous death, we provide a translation of Bongard and Smirnov’s paper on the tetrachromacy of extra-foveal vision. In a commentary, we give the background to their work and provide further details of their apparatus and procedure. We briefly discuss related research and the reception in the West of Bongard and Smirnov’s claims. We suggest that an analogy can be made between the tetrachromacy of the parafovea and the ‘weak tetrachromacy’ of heterozygotes for anomalous colour vision, whose trichromatic matches are not stable with chromatic adaptation.

Color vision tests and multi‐test protocols in current use often fail to detect small changes in red/green (RG) and yellow/blue (YB) color vision due to poor sensitivity. The tests also have low specificity. In this study, we examine how improved understanding of within‐ and inter‐subject variability in RG and YB color vision and accurate assessment of the differences in color thresholds between the least‐sensitive, age‐matched normal trichromats, and the least‐affected deutans and protans can be used to design an efficient color vision screener (CVS) test. To achieve this objective, we examined two extensive data sets from earlier studies and carried out new experiments to provide better estimates of within‐subject variability in color thresholds and to validate the CVS test. The data sets provide essential information on inter‐subject variability, the effects of normal aging on RG and YB thresholds, and the spread in RG color thresholds in deutan and protan subjects. A statistical model was developed to optimize the parameters of the CVS test and to predict the limits of what can be achieved in color assessment. The efficiency and repeatability of the CVS test were then assessed in 84 subjects. The results match model predictions and reveal close to 100% test efficiency. The test takes between 140 and 160 seconds to complete and has close to 100% repeatability. An efficient, “two‐step” protocol based on the initial use of the CVS test followed by full color assessment in only those who fail the CVS test is also described.

Traditional color vision tests depend on subjective judgments and are not suitable for infant children and subjects with cognitive dysfunction. We aimed to explore an objective and quantitative color vision testing method based on sweep steady-state visual evoked potentials (sweep SSVEPs) and compare the results with subjective Farnsworth–Munsell (FM) 100-hue test results. A red-green SSVEP pattern reversal checkboard paradigm at different luminance ratios was used to induce visual evoked potentials (VEPs) from 15 color vision deficiencies (CVDs) and 11 normal color vision subjects. After electroencephalography signals were processed by canonical correlation analysis, an equiluminance turning curve corresponding to the activation of the L-cones and M-cones at different levels of color vision was established. Then, we obtained different equiluminance T and proposed the SSVEP color vision severity index (ICVD) to quantify color vision function and the severity of CVDs. In addition, the FM 100-hue test was used to obtain subjective data for the diagnosis of color vision. The value of ICVD can be an indicator of the level of color vision. Both the total error scores (TES) and confusion index (C-index) of the FM 100-hue test were significantly correlated with ICVD values (P

Many studies have examined how color and luminance information are processed in the visual system. It has been observed that chromatic noise masked luminance discrimination in trichromats and that luminance thresholds increased as a function of noise saturation. Here, we aimed to compare chromatic noise inhibition on the luminance thresholds of trichromats and subjects with severe deutan or protan losses. Twenty-two age-matched subjects were evaluated, 12 trichromats and 10 with congenital color vision impairment: 5 protanopes/protanomalous, and 5 deuteranopes/deuteranomalous. We used a mosaic of circles containing chromatic noise consisting of 8 chromaticities around protan, deutan, and tritan confusion lines. A subset of the circles differed in the remaining circles by the luminance arising from a C-shaped central target. All the participants were tested in 4 chromatic noise saturation conditions (0.04, 0.02, 0.01, 0.005 u′v′ units) and 1 condition without chromatic noise. We observed that trichromats had an increasing luminance threshold as a function of chromatic noise saturation under all chromatic noise conditions. The subjects with color vision deficiencies displayed no changes in the luminance threshold across the different chromatic noise saturations when the noise was composed of chromaticities close to their color confusion lines (protan and deutan chromatic noise). However, for tritan chromatic noise, they were found to have similar results to the trichromats. The use of chromatic noise masking on luminance threshold estimates could help to simultaneously examine the processing of luminance and color information. A comparison between luminance contrast discrimination obtained from no chromatic and high-saturated chromatic noise conditions could be initially undertaken in this double-duty test.

Purpose. The study of color deficiencies prevalence in young people, students of higher educational university.Materials and methods. The study was carried for the half year — fall semester. A total of 1,609 students were examined, aged 17–21. There were 1191 boys and 418 girls. The survey was conducted to determine the health groups in physical training and in various sports sections. An ophthalmologic examination determined refractive disorders and other ocular pathology, which is important for determining health groups. Rabkin polychromatic tables and Neitz color vision test (Neitz Lab (UW Medicine) were used for determining of color deficiencies. The obtained results of these tests were compared in terms of the time spent on the test, the results of the test effectiveness, the determination of dissimulation, and the assessment of the shift in the color spectrum in individuals with impaired color perception.Results. A total of refractive disorders were detected in 856 students (53.2 %). The high degree of myopia was in 40. Disorders of color deficient were noted in 101 students (8.48 %) of 1191 male subjects when using the Neitz color test. Dichromatic eye changes were observed from 2.1 % students: protanopia and deiteranopia were in 0.67 % and 1.43 %. Most of all there were violations with the perception of shades of light brown and light green colors. A third of healthy students noted the impossibility of distinguishing light brown from light gray. This is regardless of the state of refraction. Simultaneous violations of the perception of shades of red, green, yellow and blue were observed in one subject, it was associated with congenital cataracts. In four young people, acquired eye diseases caused. In two girls, violations of the perception of a pastel shade of light green were noted, with one girl (0.24 %) having a violation in two eyes, and was presumably due to a gene anomaly. The second girl had one eye and was associated with partial atrophy of the optic nerve after the optic neuritis.Conclusions. Neitz color test expands the diagnostic possibilities, since in its design it has pastel shades of light green and light brown colors on a gray background, reduces the likelihood of dissimulation, reduces the time of the survey. Neitz color test allows to expand the possibilities for more accurate and differential diagnosis dichromatic and anormal trichromatic subjects and acquired color vision defects.

International audience; Certain features of both extant and fossil anthropoid primates have been interpreted as adaptations to ripe fruit foraging and feeding particularly spatulate incisors and trichromatic color vision. Here, we approach the question of anthropoid fruit foraging adaptations in light of the sensory and mechanical properties of anthropoid-consumed fruits in Kibale National Park, Uganda. We quantify the color, odor, size, and puncture resistance of fruits in Kibale that are consumed by anthropoid primates (N = 44) and compare these with the same traits of fruits that are not consumed by anthropoid primates (N = 24). Contrary to extant hypotheses, color and odor of anthropoid-consumed fruits do not differ from non-anthropoid–consumed fruits. However, we find that anthropoids in this system consume fruits that are significantly larger than non-anthropoid–consumed fruits, and with the exception of elephants that consume very large fruits, are the only dispersers of fruits with a surface area

Animal colouration is often a trade-off between background matching for camouflage from predators, and conspicuousness for communication with con- or heterospecifics. Stomatopods are marine crustaceans known to use colour signals during courtship and contests, while their overall body colouration may provide camouflage. However, we have little understanding of how stomatopods perceive these signals in their environment or whether overall body coloration does provide camouflage from predators. Neogonodactylus oerstedii assess meral spot colour during contests, and meral spot colour varies depending on local habitat. By calculating quantum catch for N. oerstedii’s 12 photoreceptors associated with chromatic vision, we found that variation in meral spot total reflectance does not function to increase signal contrast in the local habitat. Neogonodactylus oerstedii also show between-habitat variation in dorsal body colouration. We used visual models to predict a trichromatic fish predator’s perception of these colour variations. Our results suggest that sandy and green stomatopods are camouflaged from a typical fish predator in rubble fields and seagrass beds, respectively. To our knowledge, this is the first study to investigate signal contrast and camouflage in a stomatopod. These results provide new insight into the function and evolution of colouration in a species with a complex visual system.

In many butterflies, the ancestral trichromatic insect colour vision, based on UV-, blue- and green-sensitive photoreceptors, is extended with red-sensitive cells. Physiological evidence for red receptors has been missing in nymphalid butterflies, although some species can discriminate red hues well. In eight species from genera Archaeoprepona, Argynnis, Charaxes, Danaus, Melitaea, Morpho, Heliconius and Speyeria , we found a novel class of green-sensitive photoreceptors that have hyperpolarizing responses to stimulation with red light. These green-positive, red-negative (G+R–) cells are allocated to positions R1/2, normally occupied by UV and blue-sensitive cells. Spectral sensitivity, polarization sensitivity and temporal dynamics suggest that the red opponent units (R–) are the basal photoreceptors R9, interacting with R1/2 in the same ommatidia via direct inhibitory synapses. We found the G+R– cells exclusively in butterflies with red-shining ommatidia, which contain longitudinal screening pigments. The implementation of the red colour channel with R9 is different from pierid and papilionid butterflies, where cells R5–8 are the red receptors. The nymphalid red-green opponent channel and the potential for tetrachromacy seem to have been switched on several times during evolution, balancing between the cost of neural processing and the value of extended colour information.

Digital photography and spectrometry are widely used for colour measurement, but both methods have a number of advantages and disadvantages. Comparative studies can help determine the most appropriate method for quantifying animal colour perception, but few have attempted to compare them based on colour model conversion. Here we compare colour measurements from digital photography and spectrometry in a controlled standard experimental environment using the three-dimensional colour space model CIE L*a*b* which is designed to approximate colour perception in humans and assess the repeatability and agreement of the two methods. For digital photography, we first extracted RGB values from each colour patch and transferred these to L*a*b* values using colour model conversion. For spectrometry, we measured the spectral reflectance (SR) value and subsequently transferred SR values to L*a*b* values. Using a consensus of correlation analysis, intraclass correlation coefficients, concordance correlation coefficients, and Bland-Altman analysis, we found that although spectrometry showed a slightly higher repeatability than photography, both methods were highly repeatable and showed a strong agreement. Furthermore, we used Bland-Altman analysis to derive the limits of agreement, which can be used as criteria for identifying when photography and spectrometry could be as a suitable alternative for measuring colour perception in humans and other trichromatic species. We suggest that our workflow offers a practical and logical approach that could improve how we currently study colour perception in trichromats. Measuring colour efficiently and accurately is necessary for investigating the evolutionary biology of colour perception in animals. Digital photography and spectrometry are two methods widely used for colour measurement, but there are benefits and limitations to using either method. Comparative studies based on colour model conversion are therefore critical for helping researchers determine which method is most appropriate. Here we test the repeatability and agreement of the two measuring methods using standard colour patches, as a comparative case study of broader interest in measuring colour perception in humans and similar primates. Our results demonstrate that both methods are highly repeatable, and the two methods may be used interchangeably to measure colour perception in humans under experimental conditions.