Forgrundmaske

Forgrundmaske, meaning foreground mask, is a digital mask used to separate foreground elements from the background in images or video. It designates per-pixel visibility, with white or high values indicating foreground, black or zero indicating background, and gray levels representing varying levels of transparency through an alpha channel.

Mask formats typically include binary masks, grayscale masks, and alpha channels. A binary mask assigns full foreground or background, while a grayscale mask provides partial transparency that can be used for soft edges or compositing. In practice, the mask often accompanies an image as an alpha matte that determines how foreground and background layers are blended.

Creation methods range from manual to automatic. Manual approaches involve painting or rotoscoping to precisely delineate the subject. Automatic methods employ color-based segmentation, edge detection, depth maps, or semantic segmentation using machine learning to estimate the foreground regions. In video, tracking and frame-by-frame refinement (rotoscoping) are common to maintain a consistent mask over time.

Applications of forgrundmasker include image and video compositing, background replacement or removal, and selective editing such as color correction or effects applied only to the foreground. They are also used in visual effects, matte painting, and depth-of-field simulations where the foreground needs separation from the background.

Limitations include edge artifacts and noise around fine details (hair, fur, semi-transparent materials), motion blur in video, and the need for manual refinement to achieve precise results. The quality of the mask directly influences the realism of the final composite and may require post-processing to smooth edges and ensure temporal consistency.