Pixel

A digital raster image is a grid of pixels. Each pixel stores color and brightness information, commonly through red, green, and blue (RGB) channels; formats that support transparency may also store an alpha value. Multiplying an image’s width by its height gives its pixel count: a 3000 × 2000 image contains 6 million pixels. Individual pixels become noticeable when an image is enlarged beyond the detail available in its original resolution.

Pixels, camera sensor photosites, and print dots are related but not interchangeable. A photosite measures light on a camera sensor, while image processing converts sensor measurements into output pixels. PPI describes pixel density at a display or print size; DPI describes a printer’s ink-dot density. More pixels can support finer detail, but sharpness also depends on focus, optics, lighting, processing, and compression.

Image editing changes or creates pixel values. Object removal reconstructs pixels in a selected area, background removal changes transparency, and upscaling generates additional pixels from patterns in the source image. Magic Eraser can perform these edits, but generated detail is an estimate rather than recovered information from the original scene. Start with the sharpest, least-compressed source available and inspect important edges, text, and faces after editing.