Windowing

Windowing is a term used in several technical domains to denote the selection and shaping of a subset of data for processing or viewing. The core idea is to focus on a finite portion of a signal, image, or data stream by applying a window or clipping region that reduces artifacts and manages range.

In signal processing, windowing multiplies a discrete signal by a window function w[n], tapering samples toward the ends. This reduces spectral leakage when computing Fourier transforms or spectrograms. Common windows include rectangular, Hann, Hamming, Blackman, and Kaiser. There is a trade-off between main lobe width (frequency resolution) and sidelobe level (leakage). Windowing is central to the short-time Fourier transform, filter design, and numerical analysis.

In medical and scientific imaging, windowing refers to mapping the range of pixel values to display brightness and contrast, via a window level and window width. This enhances visibility of structures with different intensities and is independent of the underlying data processing.

In computer graphics, windowing describes the stage that maps 3D coordinates to 2D device coordinates, including clipping to the view window and viewport transformation. It determines which parts of a scene are rasterized and displayed on the screen.

In data analysis and streaming, windowing uses moving, or sliding, windows to compute statistics, trends, or features on subsets of data. The window size and stride control temporal locality and latency, enabling rolling averages, event detection, and real-time processing.