Human visual system model

About: Human visual system model is a research topic. Over the lifetime, 8697 publications have been published within this topic receiving 259440 citations.

Just-Noticeable Difference-Based Perceptual Optimization for JPEG Compression

Abstract: The Quantization table in JPEG, which specifies the quantization scale for each discrete cosine transform (DCT) coefficient, plays an important role in image codec optimization. However, the generic quantization table design that is based on the characteristics of human visual system (HVS) cannot adapt to the variations of image content. In this letter, we propose a just-noticeable difference (JND) based quantization table derivation method for JPEG by optimizing the rate-distortion costs for all the frequency bands. To achieve better perceptual quality, the DCT domain JND-based distortion metric is utilized to model the stair distortion perceived by HVS. The rate-distortion cost for each band is derived by estimating the rate with the first-order entropy of quantized coefficients. Subsequently, the optimal quantization table is obtained by minimizing the total rate-distortion costs of all the bands. Extensive experimental results show that the quantization table generated by the proposed method achieves significant bit-rate savings compared with JPEG recommended quantization table and specifically developed quantization tables in terms of both objective and subjective evaluations.

Distributed visual attention on a humanoid robot

Abstract: Complex visual processes such as visual attention are often computationally too expensive to allow real-time implementation on a single computer To solve this problem we study distributed computer architectures that enable us to divide complex tasks into several smaller problems In this paper we demonstrate how to implement distributed visual attention system on a humanoid robot to achieve real-time operation at relatively high resolutions and frame rates We start from a popular theory of bottom-up visual attention that assumes that information across various modalities is used for the early encoding of visual information Our system uses five different modalities including color, intensity, edges, stereo, and motion We show how to distribute the attention processing on a computer cluster and study the issues arising on such systems The system was fully implemented on a workstation cluster comprised of eight PCs It was used to drive the gaze of a humanoid head towards potential regions of interest

Adaptive local tone mapping based on retinex for high dynamic range images

Abstract: In this paper, we present a new tone mapping technique for high dynamic range images based on the retinex theory. Our algorithm consists of two steps, global adaptation and local adaptation of the human visual system. In the local adaptation process, the Gaussian filter of the retinex algorithms is substituted with a guided filter to reduce halo artifacts. To guarantee good rendition and dynamic range compression, we propose a contrast enhancement factor based on the luminance values of the scene. In addition, an adaptive nonlinearity offset is introduced to deal with the strength of the logarithm function's nonlinearity. Experiments show that our algorithm provides satisfactory results while preserving details and reducing halo artifacts.

Top-Down Visual Attention for Efficient Rendering of Task Related Scenes

Abstract: The perception of a virtual environment depends on the user and the task the user is currently performing in that environment. Models of the human visual system can thus be exploited to significantly reduce computational time when rendering high fidelity images, without compromising the perceived visual quality. This paper considers how an image can be selectively rendered when a user is performing a visual task in an environment. In particular, we investigate to what level viewers fail to notice degradations in image quality, between nontask related areas and task related areas, when quality parameters such as image resolution, edge antialiasing and reflection and shadows are altered.

Testing and treatment of visual dysfunctions

Abstract: A method for testing and treating visual dysfunctions (for example amblyopia) includes steps of providing an interactive visual game that presents to the patient a visual task, the visual game employing images scaled to the threshold visual parameter or parameters of the patient, and presenting a nonvisual reward to the patient for successful completion of the task. Also, apparatus for treating visual dysfunctions in a patient includes means for presenting an image to the patient, the image presenting a visual task to the patient, means for scaling the image to about the patient's threshold value for a visual parameter or parameters, means for providing an interaction between the patient and the image, and means for providing a reward for successful completion of the task. Also, an interactive video apparatus includes video display means for simultaneously stimulating a subject's interest and stimulating the subject's vision at about the maximum value of a visual parameter or parameters of which the subject is capable, means for receiving input from the subject, and means for providing to the subject a nonvisual reward for subject input that is appropriate to an image presented to the subject on the video display means. Also, a computerized method for testing a visual parameter or parameters comprises providing an interactive visual test that presents to the patient an image to be identified and, in step increments of increasing difficulty of the parameter in question, determining that patient's threshold value for the visual parameter or parameters by providing for interaction between the patient and the image.