Glossary

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Deconvolution

A computational process that reverses the blurring effects of convolution in an optical or imaging system. In the context of visual accessibility, deconvolution is used to pre-process images displayed on a computer screen so that when viewed through an eye with known…

Edge enhancement(also: Edge detection, Contour enhancement)

An image processing technique that identifies and highlights the boundaries between objects in a visual scene, typically rendering them as bright lines against a dark background or overlaying them on the original image. For people with low vision, edge enhancement can make…

Gaussian Blur(also: Gaussian Filter)

An image processing technique that smooths an image by averaging pixel values using a Gaussian (bell-curve) weighted function, creating a soft, out-of-focus appearance. In video accessibility, Gaussian blur is applied to video backgrounds to reduce visual distractions while…

Image Segmentation(also: Region Segmentation)

A computer vision technique that partitions a digital image into multiple distinct regions or segments based on shared characteristics such as color, intensity, or texture. In accessibility applications, image segmentation is used to simplify complex images for tactile…

Instance Segmentation

A computer vision technique that identifies and delineates individual objects within an image at the pixel level, distinguishing separate instances even when they belong to the same category. In accessibility contexts, instance segmentation enables assistive tools to provide…

Perceptual Hashing(also: Image Hashing, pHash)

A technique that generates a compact fingerprint (hash) of an image based on its visual content rather than its raw data. Unlike cryptographic hashes that change completely with any modification, perceptual hashes produce similar values for visually similar images, allowing…

Phase-Based Motion Processing(also: Phase-Based Video Motion Processing, Phase-Based Motion Magnification)

A family of computer vision techniques that decompose video frames into complex steerable pyramids and analyse changes in the temporal phase of each scale and orientation to recover motion, including sub-pixel movements invisible to the naked eye. Because it operates in the…

Point Spread Function(also: PSF)

A mathematical description of how a single point of light is spread or blurred by an optical system such as the human eye. The point spread function characterizes the degree and pattern of distortion introduced by optical aberrations. In accessibility research, PSFs are used to…

Pre-compensation(also: Display Pre-compensation, Image Pre-compensation)

A technique in which images displayed on a computer screen are mathematically modified in advance to counteract the visual aberrations of the viewer's eye. Rather than relying on corrective lenses or magnification, pre-compensation transforms the source image so that when it…

Precompensation(also: Display Precompensation, Image Precompensation)

A technique in visual accessibility that pre-modifies displayed images in a way that is opposite to the optical distortion introduced by a user's eye, so that the image arriving at the retina more closely resembles the intended original. Precompensation works analogously to an…

Semantic Segmentation(also: Pixel-Level Classification, Scene Parsing)

A computer vision technique that classifies every pixel in an image into a predefined category, producing a detailed map of what objects are present and where they are located. Unlike object detection (which draws bounding boxes around objects), semantic segmentation provides…

Spatiotemporal Saliency(also: Spatiotemporal Saliency Estimation, Spatio-Temporal Saliency)

A computer vision technique that estimates, for each pixel in a video, how visually important it is at a given moment by combining spatial contrast (features that stand out within a frame) with temporal contrast (regions that change or move differently from their recent…

Table Recognition(also: Table Detection, Table Extraction)

The automated process of detecting and reconstructing tabular data structures from document images, scanned PDFs, or other non-structured formats. Table recognition goes beyond basic OCR by identifying the spatial relationships between text elements — rows, columns, cells,…

Watershed Algorithm(also: Watershed Segmentation, Watershed Transform)

An image segmentation technique inspired by geographical hydrology, where the gradient magnitude of an image is treated as a topographical surface. The algorithm simulates water flowing downhill from each pixel to local minima, forming catchment basins that define segmented…

Zernike Polynomials(also: Zernike Coefficients, Zernike Modes)

A set of mathematical functions used to describe the shape of optical wavefronts, commonly employed in ophthalmology and optometry to characterise the optical aberrations of the human eye. Each Zernike polynomial represents a specific type of optical distortion — for example,…

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