Luminance Gradients Research Articles

Batik Pattern Classification Using Machine Learning Approaches

Batik is one of Malaysia traditional textile art form that is well known. By using Artificial Neural Network (ANN), k-Nearest Neighbors (k-NN) and Decision Tree methods, this study aims to classify Kelantan batik designs according to flora, fauna and geometry motifs. 133 images of the three categories were collected from social media and underwent pre-processing techniques. Image augmentation was done to enhance the diversity and quality of available training data for machine learning models. Digital transformation on the images based on colour features was developed to classify the three types of batik motifs. Image embedding was employed which returned a vector representation of each image in a data table in Orange software. The data divided into training and testing dataset, with a ratio of 8:2. The performance of each machine learning techniques were compared. The findings showed that ANN produced an excellent performance as indicated by classification accuracy (CA) of 87.9% for original images and 82.2% using Luminance Gradient image transformation technique. ANN also returns the highest AUC score indicating it is the best in distinguishing the images motif. Results from confusion matrix showed that ANN have the least misclassification for batik classification. Based on the result, it signifies that ANN performs the best classification among the three approaches.

Integration of motion information in illusory motion perceived in stationary patterns

Illusory motion is a phenomenon in which stationary images with repeating luminance gradient patterns appear to be moving. In this study, we conducted experiments focusing on illusory motion to verify the hypothetical rule that velocity information, extracted from local luminance patterns, is integrated by summation in visual information processing. This rule is based on the hypothesis of velocity integration, and could estimate perceived velocity of stimulus. The summation rule was evaluated by a psychophysical experiment. Our results showed that the summation rule unbiasedly predicted perceived velocity, suggesting that an algorithm for integrating velocity information in illusory motion is based on the summation rule. These results would contribute to understanding of the spatial integration of local motion signals in visual information processing.

Correction to Luzardo et al. (2023).

Reports an error in "Attention does not spread automatically along objects: Evidence from the pupillary light response" by Felipe Luzardo, Wolfgang Einhäuser, Monique Michl and Yaffa Yeshurun (Journal of Experimental Psychology: General, 2023[Jul], Vol 152[7], 2040-2051). The target stimuli were missing from Figures 1 and 2 and have now been included. The online version of this article has been corrected. (The following abstract of the original article appeared in record 2023-49083-001.) Objects influence attention allocation; when a location within an object is cued, participants react faster to targets appearing in a different location within this object than on a different object. Despite consistent demonstrations of this object-based effect, there is no agreement regarding its underlying mechanisms. To test the most common hypothesis that attention spreads automatically along the cued object, we utilized a continuous, response-free measurement of attentional allocation that relies on the modulation of the pupillary light response. In Experiments 1 and 2, attentional spreading was not encouraged because the target appeared often (60%) at the cued location and considerably less often at other locations (20% within the same object and 20% on another object). In Experiment 3, spreading was encouraged because the target appeared equally often in one of the three possible locations within the cued object (cued end, middle, uncued end). In all experiments, we added gray-to-black and gray-to-white luminance gradients to the objects. By cueing the gray ends of the objects, we could track attention. If attention indeed spreads automatically along objects, then pupil size should be greater after the gray-to-dark object is cued because attention spreads toward darker areas of the object than when the gray-to-white object is cued, regardless of the target location probability. However, unequivocal evidence of attentional spreading was only found when spreading was encouraged. These findings do not support an automatic spreading of attention. Instead, they suggest that attentional spreading along the object is guided by cue-target contingencies. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Attention does not spread automatically along objects: Evidence from the pupillary light response.

Objects influence attention allocation; when a location within an object is cued, participants react faster to targets appearing in a different location within this object than on a different object. Despite consistent demonstrations of this object-based effect, there is no agreement regarding its underlying mechanisms. To test the most common hypothesis that attention spreads automatically along the cued object, we utilized a continuous, response-free measurement of attentional allocation that relies on the modulation of the pupillary light response. In Experiments 1 and 2, attentional spreading was not encouraged because the target appeared often (60%) at the cued location and considerably less often at other locations (20% within the same object and 20% on another object). In Experiment 3, spreading was encouraged because the target appeared equally often in one of the three possible locations within the cued object (cued end, middle, uncued end). In all experiments, we added gray-to-black and gray-to-white luminance gradients to the objects. By cueing the gray ends of the objects, we could track attention. If attention indeed spreads automatically along objects, then pupil size should be greater after the gray-to-dark object is cued because attention spreads toward darker areas of the object than when the gray-to-white object is cued, regardless of the target location probability. However, unequivocal evidence of attentional spreading was only found when spreading was encouraged. These findings do not support an automatic spreading of attention. Instead, they suggest that attentional spreading along the object is guided by cue-target contingencies. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Effects of a gap between the central and surrounding regions with luminance gradients on the feeling of being dazzled.

The feeling of being dazzled is evoked by images consisting of an achromatic uniform center, surrounded by regions with luminance gradients. As the perceptual distinctness of the central region has been suggested to contribute to the feeling of being dazzled, we examined the effects of a gap between the central and surrounding regions on the feeling of being dazzled. The stimulus comprised a disk with uniform luminance surrounded by an annulus, of which the luminance was decreased from the inner boundary to the periphery. Three luminance profiles (linear, logistic, and inverse-logistic) of the surrounding luminance ramps were used. The distinctness of the disk decreased in the order of logistic, linear, and inverse-logistic profiles. The luminance of the disk, the maximum luminance of the annulus, and the gap size were also varied. When the luminance continuously transitioned from the disk to the annulus, the feeling of being dazzled was stronger for the inverse-logistic annulus luminance profile, compared with the logistic and linear profiles without a gap; however, it was not different for the three profiles with a gap. Further, the feeling of being dazzled increased when a gap was introduced for the logistic and linear profiles, but not for the inverse-logistic profile. These results suggest that the feeling of being dazzled was reduced by the perceptual indistinctness of the central disk for the logistic and linear annulus luminance profiles, while the gap restored the feeling of being dazzled by making the central disk perceptually distinct.

The switching glare illusion: Appearance and disappearance of glare effect due to figure-ground reversal.

The glare illusion is an illusory perception of brightness enhancement and self-luminosity from a glare pattern, which consists of a central white area and surrounding areas with radial darkening luminance gradients. Here, we report a phenomenon we call "the switching glare illusion." In this phenomenon, observers experience perceptual alternation in which the glare effect repeatedly appears and disappears or attenuates when the multiple glare patterns are arranged in a grid pattern. This perceptual alternation is caused by a figure-ground reversal in the grid pattern. Since such a phenomenon has not been reported for a single glare pattern, this is caused by arranging multiple glare patterns in a grid. This new finding is worthy for further studies for understanding the mechanisms underlying the glare effect and brightness perception.

A stimulus-driven approach reveals vertical luminance gradient as a stimulus feature that drives human cortical scene selectivity

Human neuroimaging studies have revealed a dedicated cortical system for visual scene processing. But what is a “scene”? Here, we use a stimulus-driven approach to identify a stimulus feature that selectively drives cortical scene processing. Specifically, using fMRI data from BOLD5000, we examined the images that elicited the greatest response in the cortical scene processing system, and found that there is a common “vertical luminance gradient” (VLG), with the top half of a scene image brighter than the bottom half; moreover, across the entire set of images, VLG systematically increases with the neural response in the scene-selective regions (Study 1). Thus, we hypothesized that VLG is a stimulus feature that selectively engages cortical scene processing, and directly tested the role of VLG in driving cortical scene selectivity using tightly controlled VLG stimuli (Study 2). Consistent with our hypothesis, we found that the scene-selective cortical regions—but not an object-selective region or early visual cortex—responded significantly more to images of VLG over control stimuli with minimal VLG. Interestingly, such selectivity was also found for images with an “inverted” VLG, resembling the luminance gradient in night scenes. Finally, we also tested the behavioral relevance of VLG for visual scene recognition (Study 3); we found that participants even categorized tightly controlled stimuli of both upright and inverted VLG to be a place more than an object, indicating that VLG is also used for behavioral scene recognition. Taken together, these results reveal that VLG is a stimulus feature that selectively engages cortical scene processing, and provide evidence for a recent proposal that visual scenes can be characterized by a set of common and unique visual features.

Classification of objects and scenes by a neural network with pretrained input modules to decode spatial texture inhomogeneities

Subject of study. The study investigated the possibility of using neural network models of second-order visual mechanisms as inputs for neural network classifiers. Second-order visual mechanisms can detect spatial inhomogeneities in the contrast, orientation, and spatial frequency of an image. These mechanisms are traditionally considered one of the stages of early visual processing; their role in the perception of textures has been well studied. Aim of study. The study aimed to investigate whether the use of classifier input modules pretrained to demodulate the spatial modulations of luminance gradients contributed to object and scene classifications. Method. Neural network modeling was used as the main method. At the first stage of the study, a set of texture images was generated to train neural network models of second-order visual mechanisms. At the second stage, the object and scene samples were prepared, based on which classifier networks were trained. Pretrained models of second-order visual mechanisms with fixed weights were applied as these network inputs. Main results. The second-order information presented as a map of instantaneous values of the modulation function of contrast, orientation, and spatial frequency of the image was sufficient for the identification of only some of the scene classes. In general, the use of the values of luminance gradient modulation functions for object classification proved to be ineffective within the proposed neural network architectural framework. Thus, the hypothesis stating that second-order visual filters encode features enabling the identification of objects was not confirmed. This result makes it necessary to test an alternative hypothesis stating that the role of second-order filters is limited to the construction of saliency maps, and filters are windows through which information is received from the first-order filter outputs. Practical significance. The possibility of using second-order models of visual mechanisms in computer vision systems was assessed.

Anisotropy in the peripheral visual field based on pupil response to the glare illusion

Visual-field (VF) anisotropy has been investigated in terms of spatial resolution of attention, spatial frequency, and semantic processing. Brightness perception has also been reported to vary between VFs. However, the influence of VF anisotropy on brightness perception using pupillometry has not been investigated. The present study measured participants' pupil size during glare illusion, in which converging luminance gradients evoke brightness enhancement and a glowing impression on the central white area of the stimulus, and halo stimuli, in which the same physical brightness of the glare illusion is used with a diverging luminance pattern. The results revealed greater stimulus-evoked pupillary dilation and glare-related dilated pupil reduction in the upper VF (UVF) compared with other VFs and halo-related pupillary changes, respectively. The stimulus-evoked pupillary dilation was affected by poor contrast sensitivity. However, owing to the superior cognitive bias formed by statistical regularity in natural scene processing of the glare illusion in the UVF, we found reduced pupillary dilation compared with the response to halo stimuli and the response from other VFs. These findings offer valuable insight into a method to reduce the potential glare effect of any VF anisotropy induced by the glare effect experienced in daily vision. An important practical implication of our study may be in informing the design of applications aimed at improving nighttime driving behavior. We also believe that our study makes a significant contribution to the literature because it offers valuable insights on VF anisotropy using evidence from pupillometry and the glare illusion.

Klaus: A study on the Application of Light and Shadow Based on Gestalt Psychology

Klaus, as a 2D animation with a 3D effect, uses light and shadow to the extreme. This paper takes the "2D shift 3D" art style of Klaus as the research object, combines the theory of "three-dimensional space created by light" in Gestalt psychology, firstly analyzes the light and shadow performance characteristics of traditional 2D animation: the simple presentation of light sources and Firstly, we analyze the characteristics of light and shadow in traditional 2D animation: the simple presentation of natural light and the application of single light source, then we introduce the factors of light affecting the composition of 3D space: luminance gradient and multiple light sources, and analyze them with the art design of Klaus. Finally, we conclude that the application of luminance gradient and multiple light sources in light is the key to rendering 3D effects in 2d images.

A multi-exposure fusion framework for contrast enhancement of hazy images employing dynamic stochastic resonance

Current imaging devices coupled with advanced hardware and software are smart enough to enhance low light images taken in clear weather. But in hazy or foggy environments, the captured images are of degraded quality. To address this issue, image processing algorithms are employed to enhance the degraded images to make useful for extracting meaningful features. In this study, we propose a haze removal algorithm to improve the color and contrast of images captured in hazy environments. The first step involves generation of images with various exposures using the theory of dynamic stochastic resonance. The images are then fused in a multi-scale fusion framework crafting weight maps viz. haze density, chromaticity, and luminance gradient. The fusion process focuses on uniformly enhancing the dark and bright regions of the image. However, it may overemphasize haze affected regions. Therefore, in the second step, the atmospheric scattering equation is referred and its modified version is applied that accomplishes the haze removal task. Quantitative and qualitative analyses demonstrate the effectiveness of the proposed method.

Revisiting the attentional bias in the split brain

Previous research has revealed a strong right bias in allocation of attention in split brain subjects, suggesting that a pathological attention bias occurs not only after unilateral (usually right-hemispheric) damage but also after functional disconnection of intact right-hemispheric areas involved in allocation of attention from those in the left hemisphere. Here, we investigated the laterality bias in spatial attention, as measured with the greyscales task, in two split-brain subjects (D.D.C. and D.D.V.) who had undergone complete callosotomy. The greyscales task requires participants to judge the darker (or brighter) of two left-right mirror-reversed luminance gradients under conditions of free viewing, and offers an efficient means of quantifying pathological attentional biases in patients with unilateral lesions. As predicted, the results of the two split-brain subjects revealed a pathological rightward bias in allocation of attention, suggesting strong dependence on a single hemisphere (the left) in spatial attention, which is opposite to what one expects from people with intact commissures, and is remarkable in that it occurs in free viewing. In that sense both split-brain patients are behaving as though the brain is indeed split, especially in D.D.C. who had undergone partial resection of the anterior commissure in addition to complete callosotomy, whereas the anterior commissure is still intact in D.D.V. The findings support the view that the commissural pathways play a significant role in integration of attentional processes across cerebral hemispheres.

Joint Gamma correction and multi-resolution fusion scheme for enhancing haze degraded images

The presence of haze degrades the quality of a captured image. The aerosols in the atmosphere cause scattering of the incident light, and this phenomenon is observed on the captured image as well, where some regions appear grayish and colors in those regions appear faded. To improve the quality of the hazy images, we propose a joint fusion and restoration model that sufficiently enhances the contrast of the hazy image while preserving its mean brightness. The fusion model utilizes images of various exposures generated by a modified Gamma correction model. The images for fusion are selected using some selection criteria and fused in a multi-resolution decomposition scheme. Three haze-sensitive weight maps corresponding to some statistical property of haze namely, saliency, illumination, and luminance gradient are constructed. The hazy image formation model is then used and dehazing is performed based on the dark channel prior assumption. The proposed algorithm does not consider the estimation of airlight vector which seldom cause over-saturation defect, instead a mean brightness preservation model has been applied. The variety of experiments demonstrate the significance of the proposed method.

Asymmetric Brightness Effects With Dark Versus Light Glare-Like Stimuli.

The glare effect is a brightness illusion that has captured the attention of the vision community since its discovery. However, its photometrical reversal, which we refer to here as photometrical reversed glare (PRG) stimuli, remained relatively unexplored. We presented three experiments that sought to examine the perceived brightness of a target area surrounded by luminance gradients in PRG stimuli and compare them with conventional glare effect configurations. Experiment 1 measured the brightness of the central target area of PRG stimuli through an adjustment task; the results showed that the target appeared brighter than similar, comparative areas not surrounded by luminance gradients. This finding was unexpected given the recent report that PRG stimuli cause pupil dilation. Meanwhile, Experiments 2 and 3 implemented a rating task to further test the findings in Experiment 1. Again, the study found a robust brightening illusion in the target area of PRG stimuli in a wide range of target and background luminance. The results are discussed in comparison with the brightness enhancement of the glare effect.

Perception of a Black Room Seen Through a Veiling Luminance.

When a black room (a room painted black and filled with objects painted black) is viewed through a veiling luminance, how does it appear? Prior work on black rooms and white rooms suggests the room will appear white because mutual illumination in the high-reflectance white room lowers image contrast, and the veil also lowers image contrast. Other work reporting high lightness constancy for three-dimensional scenes viewed through a veil suggests the veil will not make the room appear lighter. Because mutual illumination also modifies the pattern of luminance gradients across the room while the veil does not, we were able to tease apart local luminance gradients from overall luminance contrast by presenting observers with a black room viewed through a veiling luminance. The room appeared white, and no veil was perceived. This suggests that lightness judgments in a room of one reflectance depend on overall luminance contrast only.

Did Tim Paint a Vermeer?

Tim’s Vermeer is a recent documentary feature film following engineer and self-described non-artist Tim Jenison’ extensive efforts to “paint a Vermeer” by means of a novel optical telescope and mirror-comparator procedure. His efforts were inspired by the controversial claim that some Western painters as early as 1420 secretly built optical devices and traced passages in projected images during the execution of some of their works, thereby achieving a novel and compelling “optical look.” The authors examine the proposed telescope optics in historical perspective, the particular visual evidence adduced in support of the comparator hypothesis, and the difficulty and efficacy of the mirror-comparator procedure as revealed by an independent artist/copyist’s attempts to replicate the procedure. Specifically, the authors find that the luminance gradient along the rear wall in the duplicate painting is far from being rare, difficult, or even “impossible” to achieve as proponents claimed; in fact, such gradients appear in numerous Old Master paintings that show no ancillary evidence of having been executed with optics. There is indeed a slight bowing of a single contour in the Vermeer original, which one would normally expect to be straight; however, the optical explanation for this bowing implies that numerous other lines would be similarly bowed, but in fact all are straight. The proposed method does not explain some ofthe most compelling “optical” evidence in Vermeer’s works suchas the small disk-shaped highlights, which appear like the blur spots that arise in an out-of-focus projected image. Likewise, the comparator-based explanations for the presence of pinprick holes at central vanishing points and the presence of underdrawings and pentimenti in several of Vermeer’s works have more plausible non-optical explanations. Finally, an independent experimentalattempt to replicate the procedure fails overall to provide support for the telescope claim. In light of these considerations and evidence, the authors conclude that it is extremely unlikely that Vermeer used the proposed mirror-comparator procedure.

Mechanism for analogous illusory motion perception in flies and humans

Visual motion detection is one of the most important computations performed by visual circuits. Yet, we perceive vivid illusory motion in stationary, periodic luminance gradients that contain no true motion. This illusion is shared by diverse vertebrate species, but theories proposed to explain this illusion have remained difficult to test. Here, we demonstrate that in the fruit fly Drosophila, the illusory motion percept is generated by unbalanced contributions of direction-selective neurons' responses to stationary edges. First, we found that flies, like humans, perceive sustained motion in the stationary gradients. The percept was abolished when the elementary motion detector neurons T4 and T5 were silenced. In vivo calcium imaging revealed that T4 and T5 neurons encode the location and polarity of stationary edges. Furthermore, our proposed mechanistic model allowed us to predictably manipulate both the magnitude and direction of the fly's illusory percept by selectively silencing either T4 or T5 neurons. Interestingly, human brains possess the same mechanistic ingredients that drive our model in flies. When we adapted human observers to moving light edges or dark edges, we could manipulate the magnitude and direction of their percepts as well, suggesting that mechanisms similar to the fly's may also underlie this illusion in humans. By taking a comparative approach that exploits Drosophila neurogenetics, our results provide a causal, mechanistic account for a long-known visual illusion. These results argue that this illusion arises from architectures for motion detection that are shared across phyla.

Horizontal and vertical perceptual asymmetries for the grayscale task in healthy Japanese young adults

The grayscale task requires participants to make forced-choice luminance judgments of two mirror-reversed luminance gradients. Neurologically healthy left-to-right readers in Western countries, show strong leftward and upward attentional biases in the horizontal and vertical conditions, respectively. In this study, we examined the grayscale task performance of young adults whose native language was Japanese, a language with complex writing rules including changes in the directionality of reading. Additionally, we examined the effects of sex, handedness, and hand used. Half (64 men and 64 women) of the participants included in this study were left-handed. Participants were administered a paper version of the grayscale task in horizontal and vertical conditions. As with left-to-right readers, respective leftward and upward biases were observed in the two conditions. The main effects of sex, handedness, and hand used and the possible interactions among the three variables were non-significant for either condition. The results of this study can be used as basic data for the application of this task to clinical and analog research in neuropsychiatric and developmental disorders in Japan.

Countershading enhances camouflage by reducing prey contrast

A three-dimensional body shape is problematic for camouflage because overhead lighting produces a luminance gradient across the body's surface. Countershading, a form of patterning where animals are darkest on their uppermost surface, is thought to counteract this luminance gradient and enhance concealment, but the mechanisms of protection remain unclear. Surprisingly, no study has examined how countershading alters prey contrast, or investigated how the presence of a dorsoventral luminance gradient affects detection under controlled viewing conditions. It has also been suggested that the direction of the dorsoventral luminance gradient (darkest or lightest on top) may interfere with predators' abilities to resolve prey's three-dimensional shape, yet this intriguing idea has never been tested. We used live fish predators (western rainbowfish, Melanotaenia australis) and computer-generated prey images to compare the detectability of uniformly pigmented (i.e. non-countershaded) prey with that of optimally countershaded prey of varying contrasts against the background. Optimally countershaded prey were difficult for predators to detect, and the probability and speed of detection depended on prey luminance contrast with the background. In comparison, non-countershaded prey were always highly detectable, even though their average luminance closely matched the luminance of the background. Our findings suggest that uniformly pigmented three-dimensional prey are highly conspicuous to predators because overhead lighting increases luminance contrast between different body parts or between the body and the background. We found no evidence for the notion that countershading interferes with predator perception of three-dimensional form.

The influence of object structure on visual short-term memory for multipart objects.

Numerous studies have shown that more visual features can be stored in visual short-term memory (VSTM) when they are encoded from fewer objects (Luck & Vogel, 1997, Nature, 390, 279-281; Olson & Jiang, 2002, Perception & Psychophysics, 64[7], 1055-1067). This finding has been consistent for simple objects with one surface and one boundary contour, but very few experiments have shown a clear performance benefit when features are organized as multipart objects versus spatially dispersed single-feature objects. Some researchers have suggested multipart object integration is not mandatory because of the potential ambiguity of the display (Balaban & Luria, 2015, Cortex, 26(5), 2093-2104; Luria & Vogel, 2014, Journal of Cognitive Neuroscience, 26[8], 1819-1828). For example, a white bar across the middle of a red circle could be interpreted as two objects, a white bar occluding a red circle, or as a single two-colored object. We explore whether an object benefit can be found by disambiguating the figure-ground organization of multipart objects using a luminance gradient and linear perspective to create the appearance of a unified surface. Also, we investigated memory for objects with a visual feature indicated by a hole, rather than an additional surface on the object. Results indicate the organization of multipart objects can influence VSTM performance, but the effect is driven by how the specific organization allows for use of global ensemble statistics of the memory array rather than a memory benefit for local object representations.