Glossary

Alpha Channel

Alpha Channel (Transparency Mask)

An alpha channel stores transparency information for each pixel in an image, with values ranging from fully transparent to fully opaque. It is the fourth channel in RGBA color, enabling smooth blending of images over backgrounds.

Alpha Compositing

Combining semi-transparent images by blending pixel colors according to their alpha channel values.

Aspect Ratio

Aspect Ratio (Width-to-Height Proportion)

Aspect ratio is the proportional relationship between an image's width and height, expressed as two numbers separated by a colon. Common ratios include 16:9 (widescreen), 4:3 (classic), and 1:1 (square).

AVIF

AV1 Image File Format

A next-generation image format based on the AV1 video codec, offering superior compression.

Batch Resize

Batch Image Resize

Processing multiple images at once to change their dimensions to a uniform size or percentage of the original.

Bit Depth

Bit Depth (Color Depth / Bits Per Pixel)

Bit depth determines the number of possible color values each pixel can represent. Higher bit depths allow more colors and smoother gradients: 8-bit provides 256 values per channel (16.7M colors), while 16-bit provides 65,536.

Canvas

Canvas (Image Working Area)

In image editing, the canvas is the total working area that defines the boundaries of the image. Resizing the canvas adds or removes space around the existing image content without scaling it.

Chroma Subsampling

Chroma Subsampling (Color Resolution Reduction)

Chroma subsampling reduces the color resolution of an image while preserving full brightness (luminance) detail. Human eyes are less sensitive to color changes than brightness changes, making this an efficient compression technique.

Chromatic Aberration

A lens defect causing color fringing at edges where different wavelengths of light focus at slightly different points.

Color Grading (Image)

Image Color Grading

Adjusting color balance, contrast, and tone curves to achieve a desired mood or visual style in an image.

Color Profile

Color Profile (ICC Profile)

A color profile defines how numerical color values map to actual colors on a specific device. ICC profiles ensure colors look consistent across different monitors, printers, and cameras by providing a standardized color interpretation.

Color Space

Color Space (Color Model)

A color space is a specific organization of colors that defines the gamut (range) of representable colors. sRGB is the web standard, Adobe RGB covers more greens and cyans for print, and Display P3 serves modern wide-gamut displays.

Compression Artifact

Compression Artifact (Visual Distortion)

Compression artifacts are visible distortions introduced by lossy compression algorithms. Common artifacts include blockiness (JPEG macroblocks), ringing around sharp edges, color banding in gradients, and mosquito noise.

Content-Aware Fill

An AI-powered technique that removes objects from images by intelligently filling the gap with surrounding pixels.

Convolution

Convolution (Image Filter Kernel Operation)

Convolution is the fundamental operation behind image filters like blur, sharpen, and edge detection. A small matrix (kernel) slides across the image, computing weighted sums of neighboring pixels to produce the output.

Crop

Image Crop

The removal of outer areas from an image to change its composition, aspect ratio, or focus.

Dithering (Image)

Image Dithering

A technique that simulates additional colors by arranging limited-palette pixels in patterns that blend visually.

DPI

Dots Per Inch

A measure of print resolution indicating how many dots of ink are placed per inch.

DPI/PPI

DPI/PPI (Dots/Pixels Per Inch)

DPI (dots per inch) and PPI (pixels per inch) measure image resolution density. PPI describes screen display density, while DPI refers to print output resolution. 72 PPI is standard for web, 300 DPI for print.

EXIF

EXIF (Exchangeable Image File Format)

EXIF is a metadata standard embedded in JPEG, TIFF, and RAW files that records camera settings and shooting conditions. It stores data like shutter speed, aperture, ISO, GPS location, date, camera model, and lens information.

Feature Matching

Image Feature Matching

Finding corresponding keypoints between two images for alignment, stitching, or 3D reconstruction.

Focus Stacking

Combining multiple images shot at different focus distances to produce one image with greater depth of field.

Gamma

Gamma (Brightness Transfer Function)

Gamma describes the nonlinear relationship between pixel values and displayed brightness. A gamma of 2.2 (the sRGB standard) means that pixel value 128 is not 50% brightness but approximately 21.8%, matching human perception.

Gamut Mapping

Color Gamut Mapping

The process of converting colors from one color space to another while handling out-of-gamut colors gracefully.

HDR

High Dynamic Range

An imaging technique that captures and displays a wider range of brightness levels than standard imaging.

Histogram

Histogram (Tonal Distribution Graph)

An image histogram is a graph showing the distribution of pixel brightness values from shadows (left) to highlights (right). Photographers and editors use histograms to evaluate exposure, contrast, and tonal balance.

ICC Profile

ICC Profile (International Color Consortium Profile)

An ICC profile is a standardized data file that characterizes a color device (monitor, printer, scanner) or color space. Embedding ICC profiles in images ensures that colors are reproduced accurately across different devices.

Image Histogram

A graphical representation of pixel intensity distribution in an image, used to assess exposure and contrast.

Image Interpolation

Image Interpolation (Pixel Resampling)

Image interpolation is the method used to calculate new pixel values when resizing an image. Different algorithms (nearest-neighbor, bilinear, bicubic, Lanczos) trade speed for quality when scaling images up or down.

Image Optimization

The process of reducing image file size while maintaining acceptable visual quality for web delivery.

Image Pyramid

A multi-scale representation of an image at progressively lower resolutions, used in image analysis and blending.

Image Registration

Aligning two or more images of the same scene taken at different times, viewpoints, or by different sensors.

Image Segmentation

Partitioning an image into multiple regions or objects, used in computer vision for scene understanding.

IPTC

International Press Telecommunications Council Metadata

A metadata standard for news photos including caption, creator, copyright, and keyword information.

Lossless Compression

Lossless Compression (Reversible Data Reduction)

Lossless compression reduces file size without discarding any image data. The original image can be perfectly reconstructed from the compressed file. PNG, TIFF (with LZW), and WebP lossless use this approach.

Lossy Compression

Lossy Compression (Perceptual Data Reduction)

Lossy compression achieves much smaller file sizes by permanently discarding image data that is less perceptible to human vision. JPEG, WebP lossy, and AVIF use this approach to achieve 10:1 to 50:1 compression ratios.

Metadata

Metadata (Image Descriptive Data)

Image metadata is information embedded within an image file that describes its properties, origin, and content. This includes EXIF camera data, IPTC editorial information, XMP descriptive tags, and ICC color profiles.

Mipmap

Mipmap (Multum In Parvo)

A set of pre-computed, progressively smaller versions of a texture used to improve rendering speed and reduce aliasing.

Morphological Operations

Morphological Image Operations

Image processing operations (erosion, dilation, opening, closing) that modify shapes based on a structuring element.

Noise Reduction (Image)

Image Noise Reduction

Techniques for removing unwanted grain or artifacts from images caused by high ISO or low-light conditions.

Object Detection

A computer vision task that identifies and locates objects within an image using bounding boxes and class labels.

Panorama Stitching

Panorama Image Stitching

Combining multiple overlapping photographs into a single wide-angle or 360-degree panoramic image.

Raster Graphics

Images composed of a grid of pixels, where each pixel has a specific color value.

Rasterization

Rasterization (Vector-to-Pixel Conversion)

Rasterization is the process of converting vector graphics (mathematical shapes) into raster images (pixel grids). This is necessary when displaying SVG, PDF, or font glyphs on pixel-based screens or exporting to bitmap formats.

Resize

Image Resize

Changing the dimensions of an image, which may involve interpolation to add or remove pixels.

Resolution

Image Resolution

The number of pixels in an image, typically expressed as width × height (e.g. 1920×1080).

Sprite Sheet

CSS Sprite Sheet

A single image containing multiple smaller images, used to reduce HTTP requests in web development.

Texture Atlas

A large image containing many smaller sub-images, used in 3D graphics and games to reduce draw calls.