alphablend

Alphablend is a term used in computer graphics and image processing to describe the blending of two images or colors based on an alpha channel. The alpha channel is essentially a transparency mask, where each pixel's alpha value determines how opaque or transparent it is. When alphablending occurs, the color of a pixel in the foreground image is combined with the color of the corresponding pixel in the background image. The degree of blending is controlled by the alpha value of the foreground pixel. A fully opaque foreground pixel will completely obscure the background pixel, while a fully transparent foreground pixel will be invisible, showing only the background. Partially transparent pixels will result in a mix of the foreground and background colors, with the proportion of each determined by the alpha value.

This technique is fundamental to creating effects like fading, transparency, and compositing in digital media. It allows for seamless integration of images, layered graphics, and realistic visual effects in software applications ranging from image editors to video games. The mathematical operation behind alphablending typically involves multiplying the foreground color by its alpha value and adding the background color multiplied by one minus the foreground pixel's alpha value. This ensures that the combined color is a weighted average of the two source colors, respecting the transparency information provided by the alpha channel. Alphablending is a core component in many graphics rendering pipelines and file formats, such as PNG, which natively support alpha channels.