Alpha compositing

Alpha compositing combines foreground and background image samples using alpha values that represent coverage or transparency, producing a new color and alpha value.

Porter–Duff compositing: A family of image-compositing operators that combine source and destination colors and alpha values. Its operators formalize the rules used to combine foreground and background layers.
Digital image: An image represented as a finite arrangement of digitally encoded samples. Compositing operates on corresponding samples in digital image layers.
Compositing (visual effects): The assembly of visual elements from separate sources into a finished film or video image. Alpha compositing is a basic operation for integrating effects with photographed footage.
Additive blending: A blend operation that adds color values from two image samples. It combines light contributions rather than weighting a foreground by opacity.
Color fringing: Unwanted colored edges that appear around image features or boundaries. Incorrect handling of transparent edge colors can create fringes after compositing.
Alpha channel: An image channel storing per-pixel alpha values, commonly used to represent opacity or coverage. The alpha channel supplies the values that control each layer’s contribution.
Pixel: A sample representing color or other image information at a location in a raster image. Compositing usually computes a new color and alpha for each pixel.
Digital compositing: The combination of visual elements from multiple digital sources into one image or sequence. Its image assembly workflows rely on alpha-aware layer operations.
Screen (blending mode): A blend mode that inverts, multiplies, and reinverts two color values to create a lighter result. Screen changes color interaction but is not itself an alpha compositing rule.
Alpha premultiplication artifact: A visible image defect caused by inconsistent treatment of premultiplied and straight alpha values. Mixing alpha conventions can produce dark or bright halos at translucent edges.

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