A filter is a digital effect used to modify image pixels and selections. Algorithms control modifications by altering pixelPixels are the smallest unit of a digital display or digital image. A raster or bitmap image is made... More values or arrangement. Filters can clean up or retouchRetouch refers to the process of digitally removing unwanted imperfections or objects in an image. More photos, apply special art effects, or create unique transformations using distortions and lighting effects.