What is aliasing and anti-aliasing?
Digital images are made by displaying tiny dots on a (usually) rectilinear grid. Straight lines which go in either horizontal or vertical directions on this grid will always look fine, but diagonal lines can be a problem. Since such lines essentially cut across the grid pattern they can appear as rough jagged stair-step lines rather than smooth diagonal lines. There are three common ways of reducing this effect. First, if the resolution of the image is high enough (ie: each individual pixel is small enough) then the aliasing will not be readily apparent to the human eye. Second, the jagged lines can be smoothed out by filling in the stairsteps with intermediate (eg: grey rather than black and white) values. Computer software that performs this function is commonly known as an anti-aliasing algorithm . Third, most digital cameras contain optical filters situated between the lens and the image sensor which smooth out the jaggies optically before it s recorded by the sensor. Such anti-ali
